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The genus Eigenmannia Jordan et Evermann,1896 includes electric fishes endemic to the Neotropical region with extensive karyotype variability and occurrence of different sex chromosome systems, however, cytogenetic studies within this group are restricted to few species. Here, we describe the karyotypes of Eigenmannia limbata (Schreiner et Miranda Ribeiro, 1903) and E. microstoma (Reinhardt, 1852) and the chromosomal locations of 5S and 18S rDNAs (ribosomal RNA genes) and U2 snDNA (small nuclear RNA gene). Among them, 18S rDNA sites were situated in only one chromosomal pair in both species, and co-localized with 5S rDNA in E. microstoma. On the other hand, 5S rDNA and U2 snRNA sites were observed on several chromosomes, with variation in the number of sites between species under study. These two repetitive DNAs were observed co-localized in one chromosomal pair in E. limbata and in four pairs in E. microstoma. Our study shows a new case of association of these two types of repetitive DNA in the genome of Gymnotiformes.

Eigenmannia desantanai Peixoto, Dutra & Wosiacki, 2015: 393, fig. 7. Paratypes: 2 lots, 19 specimens —NUP 3470, 9 + 1 c&s, 119.8–142.8 mm LEA: Brazil, Mato Grosso, Santo Antônio do Leverger, rio Cuiabá, rio Paraguai basin, 15°58’26”S, 55°56’26”W, Nupélia staff, 24 Oct 2002. NUP 12500, 9, 78.3–106.1 mm LEA: Brazil, Mato Grosso, Barão do Melgaço, rio Cuiabá, baía de Chacororé, rio Paraguai basin, 16°14’58.9”S, 55°52’44.4” W, Nupélia staff, 20 Oct 2003., Published as part of De Oliveira, Rianne C., Ota, Renata R., Deprá, Gabriel C., Zawadzki, Cláudio H., Pavanelli, Carla S. & Da Graça, Weferson J., 2022, Catalog of type specimens of the fish collection of the Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (NUP), Universidade Estadual de Maringá Paraná, Brazil, pp. 1-43 in Zootaxa 5128 (1) on page 10, DOI: 10.11646/zootaxa.5128.1.1, http://zenodo.org/record/6479497, {"references":["Peixoto, L. A. W., Dutra, G. M. & Wosiacki, W. B. (2015) The electric glass knifefishes of the Eigenmannia trilineata speciesgroup (Gymnotiformes: Sternopygidae): monophyly and description of seven new species. Zoological Journal of the Linnean Society, 175 (2), 384 - 414. https: // doi. org / 10.1111 / zoj. 12274"]}

Eigenmannia pavulagem Peixoto, Dutra & Wosiacki, 2015: 403, fig. 17. Paratypes: 1 lot, 2 specimens — NUP 17104, 2, 82.7–114.7 mm LEA: Pará, Paragominas, igarapé Paraquequara, tributary of rio Capim, rio Guamá basin, 3°14’50”S, 47°45’50” W, A. Souza, 16 Apr 2003., Published as part of De Oliveira, Rianne C., Ota, Renata R., Deprá, Gabriel C., Zawadzki, Cláudio H., Pavanelli, Carla S. & Da Graça, Weferson J., 2022, Catalog of type specimens of the fish collection of the Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (NUP), Universidade Estadual de Maringá Paraná, Brazil, pp. 1-43 in Zootaxa 5128 (1) on page 10, DOI: 10.11646/zootaxa.5128.1.1, http://zenodo.org/record/6479497, {"references":["Peixoto, L. A. W., Dutra, G. M. & Wosiacki, W. B. (2015) The electric glass knifefishes of the Eigenmannia trilineata speciesgroup (Gymnotiformes: Sternopygidae): monophyly and description of seven new species. Zoological Journal of the Linnean Society, 175 (2), 384 - 414. https: // doi. org / 10.1111 / zoj. 12274"]}

Animals vary considerably in size, shape, and physiological features across individuals, but yet achieve remarkably similar behavioral performances. We examined how animals compensate for morphophysiological variation by measuring the system dynamics of individual knifefish (Eigenmannia virescens) in a refuge tracking task. Kinematic measurements of Eigenmannia were used to generate individualized estimates of each fish’s locomotor plant and controller, revealing substantial variability between fish. To test the impact of this variability on behavioral performance, these models were used to perform simulated ‘brain transplants’—computationally swapping controllers and plants between individuals. We found that simulated closed-loop performance was robust to mismatch between plant and controller. This suggests that animals rely on feedback rather than precisely tuned neural controllers to compensate for morphophysiological variability., eLife digest People come in different shapes and sizes, but most will perform similarly well if asked to complete a task requiring fine manual dexterity – such as holding a pen or picking up a single grape. How can different individuals, with different sized hands and muscles, produce such similar movements? One explanation is that an individual’s brain and nervous system become precisely tuned to mechanics of the body’s muscles and skeleton. An alternative explanation is that brain and nervous system use a more “robust” control policy that can compensate for differences in the body by relying on feedback from the senses to guide the movements. To distinguish between these two explanations, Uyanik et al. turned to weakly electric freshwater fish known as glass knifefish. These fish seek refuge within root systems, reed grass and among other objects in the water. They swim backwards and forwards to stay hidden despite constantly changing currents. Each fish shuttles back and forth by moving a long ribbon-like fin on the underside of its body. Uyanik et al. measured the movements of the ribbon fin under controlled conditions in the laboratory, and then used the data to create computer models of the brain and body of each fish. The models of each fish’s brain and body were quite different. To study how the brain interacts with the body, Uyanik et al. then conducted experiments reminiscent of those described in the story of Frankenstein and transplanted the brain from each computer model into the body of different model fish. These “brain swaps” had almost no effect on the model’s simulated swimming behavior. Instead, these “Frankenfish” used sensory feedback to compensate for any mismatch between their brain and body. This suggests that, for some behaviors, an animal’s brain does not need to be precisely tuned to the specific characteristics of its body. Instead, robust control of movement relies on many seemingly redundant systems that provide sensory feedback. This has implications for the field of robotics. It further suggests that when designing robots, engineers should prioritize enabling the robots to use sensory feedback to cope with unexpected events, a well-known idea in control engineering.

Eigenmannia is one of the more taxonomically complex genera within the Gymnotiformes. Here we adopt an integrative taxonomic approach, combining osteology, COI gene sequences, and geometric morphometrics to describe three new species belonging to the E. trilineata species group from Colombian trans-Andean region. These new species increase the number of species in the E. trilineata complex to 18 and the number of species in the genus to 25. The distribution range of the E. trilineata species group is expanded to include parts of northwestern South America and southern Central America. RESUMEN Eigenmannia es uno de los géneros taxonómicamente más complejos dentro de los Gymnotiformes. En este artículo adoptamos un enfoque taxonómico integrador, que combina osteología, secuencias del gene COI y morfometría geométrica, para describir tres nuevas especies que pertenecen al grupo de especies de E. trilineata de la región transandina de Colombia. Estas nuevas especies aumentan el número de especies en el complejo E. trilineata a 18 y el número de especies en el género a 25. El rango de distribución del grupo de especies de E. trilineata se ha expandido al noroeste de Sudamérica y el sur de América Central.

Field studies on freely behaving animals commonly require tagging and often are focused on single species. Weakly electric fish generate a species- and individual-specific electric organ discharge (EOD) and therefore provide a unique opportunity for individual tracking without tagging. We here present and test tracking algorithms based on recordings with submerged electrode arrays. Harmonic structures extracted from power spectra provide fish identity. Localization of fish based on weighted averages of their EOD amplitudes is found to be more robust than fitting a dipole model. We apply these techniques to monitor a community of three species,Apteronotus rostratus,Eigenmannia humboldtii, andSternopygus dariensis, in their natural habitat in Darién, Panamá. We found consistent upstream movements after sunset followed by downstream movements in the second half of the night. Extrapolations of these movements and estimates of fish density obtained from additional transect data suggest that some fish cover at least several hundreds of meters of the stream per night. Most fish, includingEigenmannia, were traversing the electrode array solitarily. Fromin-situmeasurements of the decay of the EOD amplitude with distance of individual animals we estimated that fish can detect conspecifics at distances of up to 2 m. Our recordings also emphasize the complexity of natural electrosensory scenes resulting from the interactions of the EODs of different species. Electrode arrays thus provide an unprecedented window into the so-far hidden nocturnal activities of multispecies communities of weakly electric fish at an unmatched level of detail.Summary statementDetailed movement patterns and complex electrosensory scenes of three species of weakly electric fish were tracked without tagging using a submerged electrode array in a small Neotropical stream.

We report four mitochondrial genomes of South American electric knifefishes, derived from target capture and Illumina sequencing (HiSeq 2500 PE100). Two trans-Andean species Eigenmannia humboldtii (mitochondrial consensus genome of 25 individuals) and Sternopygus aequilabiatus (mitochondrial consensus genome of 30 individuals) from Colombia and two cis-Andean species Eigenmannia limbata from Suriname and Sternopygus macrurus from Argentina. Regarding Eigenmannia humboldtii, Eigenmannia limbata, and Sternopygus macrurus mitochondrial genomes have 13 protein-coding genes, 1 D-loop, 2 ribosomal RNAs, 22 transfer RNAs, and are 13,394 bp, 10,921 bp, and 13,013 bp in length respectively, for Sternopygus aequilabiatus mitochondrial genomes have 13 protein-coding genes, 2 ribosomal RNAs, 22 transfer RNAs, and is 14,270 bp in length.

Glass knifefish (Eigenmannia) are a group of weakly electric fishes found throughout the Amazon basin. Their electric organ discharges (EODs) are energetically costly adaptations used in social communication and for localizing conspecifics and other objects including prey at night and in turbid water. Interestingly, a troglobitic population of blind cavefish Eigenmannia vicentespelea survives in complete darkness in a cave system in central Brazil. We examined the effects of troglobitic conditions, which includes a complete loss of visual cues and potentially reduced food sources, by comparing the behavior and movement of freely behaving cavefish to a nearby epigean (surface) population (Eigenmannia trilineata). We found that the strengths of electric discharges in cavefish were greater than in surface fish, which may result from increased reliance on electrosensory perception, larger size, and sufficient food resources. Surface fish were recorded while feeding at night and did not show evidence of territoriality, whereas cavefish appeared to maintain territories. Surprisingly, we routinely found both surface and cavefish with sustained differences in EOD frequencies that were below 10 Hz despite being within close proximity of about 50 cm. A half century of analysis of electrosocial interactions in laboratory tanks suggest that these small differences in EOD frequencies should have triggered the “jamming avoidance response,” a behavior in which fish change their EOD frequencies to increase the difference between individuals. Pairs of fish also showed significant interactions between EOD frequencies and relative movements at large distances, over 1.5 m, and at high differences in frequencies, often >50 Hz. These interactions are likely “envelope” responses in which fish alter their EOD frequency in relation to higher order features, specifically changes in the depth of modulation, of electrosocial signals.

A new species of Eigenmannia is described from the rio Mutum, tributary of upper rio Juruena, rio Tapajós basin, Comodoro, Mato Grosso, Brazil. The new species is distinguished from all congeners by coloration pattern, position of the mouth, number of scales rows above lateral line, number of premaxillary and dentary teeth, number of precaudal vertebrae, orbital diameter, mouth width, relative depth of posterodorsal expansion on infraorbitals 1+2 and relative size of coronomeckelian bone. Comments on potentially useful characters in phylogenetic studies derived from musculature, discussion on Eigenmannia species-group and the first dichotomous key for Eigenmannia are provided.

Made available in DSpace on 2018-12-11T16:40:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-02-01 This study provides the most comprehensive Model-Based Total Evidence (MBTE) phylogenetic analyses of the clade Gymnotiformes to date, reappraising relationships using a dataset comprised of six genes (5277 bp) and 223 morphological characters, and an ingroup taxon sample including 120 of 212 valid species representing 34 of the 35 extant genera. Our MBTE analyses indicate the two main gymnotiform clades are Gymnotidae and Sternopygoidei, the latter comprised of Rhamphichthyoidea (Rhamphichthyidae + Hypopomidae) and Sinusoidea (Sternopygidae + Apteronotidae). Within Gymnotidae, Electrophorus and Gymnotus are sister taxa, and Gymnotus includes the following six clades: (i) G. pantherinus clade, (ii) G. coatesi clade, (iii) G. anguillaris clade, (iv) G. tigre clade, (v) G. cylindricus clade, and (vi) G. carapo clade. Within Rhamphichthyoidea, Steatogenae (Steatogenys + Hypopygus) is a member of Rhamphichthyidae, and Hypopomidae includes the following clades: (i) Akawaio, (ii) Hypopomus, (iii) Microsternarchini, and (iv) Brachyhypopomus. Within Sternopygidae, Sternopygus and Eigenmanninae are sister groups, Rhabdolichops is the sister to other Eigenmanninae, Archolaemus+. Distocyclus is the sister to Eigenmannia, and Japigny is nested within Eigenmannia. Within Apteronotidae, Sternarchorhamphinae (Sternarchorhamphus + Orthosternarchus) is the sister to Apteronotinae, Adontosternarchus is the sister group to other Apteronotinae, Sternarchorhynchini (Sternarchorhynchus + Platyurosternarchus) is the sister to Navajini, and species assigned to Apteronotus are members of two separate clades: (i) A. sensu stricto in the Apteronotini, and (ii) the A. bonapartii clade in the Navajini. Universidade Estadual Paulista - UNESP Instituto de Biociências de Botucatu University of Louisiana at Lafayette Department of Biology Universidade Estadual Paulista - UNESP Instituto de Biociências de Botucatu

Eigenmannia oradens, new species Figs. 1��� 3, Table 1 Holotype. ANSP 190768, xr, 121.6 mm LEA, Venezuela, Amazonas, R��o Ventuari at Raudales Chipirito, 88.5 Km east of San Fernando de Atabapo, 04��04���6���N 66��54���13���W, 0 1 April 2010, M. Sabaj-P��rez, N.K. Lujan, D.C. Werneke, T. Carvalho, S. Meza V., A. Luna & O. Santaella. Paratypes. ANSP 190912, 2 xr, 62.6���101.1 mm LEA, Venezuela, Amazonas, R��o Ventuari ca. 20 airmiles NE of confluence with R��o Orinoco, near ornamental fish market in river, 04��04���32���N 66��53���34���W, 0 3 April 2005, N.K. Lujan, M. Arce, E.L. Richmond, M.P. Grant & T.E. Wesley. ANSP 203212, 1xr, 76.7 mm LEA, collected with the holotype, MPEG 35287, 1xr+1CS, 94.7���111.1 mm LEA, collected with the holotype. MZUSP 122802, 1MS, 102.3 mm LEA, collected with the holotype. USNM 440377, 1xr, 91.4 mm LEA, collected with the holotype. Diagnosis. Eigenmannia oradens differs from all congeners by presence of bony dorsolateral flange of dentary which also anchors numerous teeth along its extension (versus dorsolateral flange absent and teeth are attached only in dentary rim), and first premaxillary teeth row mobile, teeth attached to anteroventral margin of premaxilla (versus first premaxillary teeth row immobile, teeth completely attached to ventral surface of premaxilla). It is further distinguished from remain congeners, except E. besouro Peixoto & Wosiacki, 2016, E. correntes Camposda-Paz & Queiroz, 2017, E. meeki Dutra, de Santana & Wosiacki, 2017, E. vicentespelaea Triques, 1996, E. virescens Valenciennes, 1836, and E. waiwai Peixoto, Dutra & Wosiacki, 2015 by the subterminal mouth (versus terminal: Fig. 2). The new species is diagnosed from E. besouro, E. correntes, E. meeki, E. vicentespelaea, and E. virescens by having 38���42 teeth on premaxilla (versus 18���29 in E. besouro, 17���20 in E. correntes, 30���35 in E. meeki, 25���26 in E. vicentespelaea, and 22 in E. virescens). It is distinguished from E. besouro, E. correntes, E. meeki, E. virescens, and E. waiwai by the coronomeckelian bone corresponding to 45% of length of Meckel���s cartilage (versus 20% of length of Meckel���s cartilage in E. correntes, E. meeki, E. virescens and E. waiwai and 30% of length of Meckel���s cartilage in E. besouro). Eigenmannia oradens also differs from E. meeki, E. vicentespelaea, and E. waiwai by having 99���107 scales along lateral line until the end of anal fin (versus 140���168 in E. meeki, 110���125 in E. vicentespelaea, and 111���128 in E. waiwai). It is further distinguished from E. besouro, E. correntes, E. vicentespelaea and E. waiwai by absence of superior midlateral stripe (versus presence). The new species is additionally diagnosed from E. meeki, E. virescens, and E. waiwai by depth of posterodorsal expansion on infraorbitals 1+2 approximately equal to total length of infraorbitals 1+2 (versus less than 50% of the length of infraorbitals 1+2). Eigenmannia oradens also differs from E. besouro, E. correntes and E. waiwai by having ii, 16���17 pectoral fin rays (versus ii, 13���14 in E. besouro, ii, 11���12 in E. correntes, and ii, 13���15 in E. waiwai). It is distinguished from E. correntes and E. meeki by having 31���38 dentary teeth (versus 16���18 and 20���23 respectively), and 164���192 anal-fin rays (versus 211���240). It also differs from E. virescens by presence of narrow stripe on lateral line (versus absence). Eigenmannia oradens is diagnosed from E. waiwai by having 14 precaudal vertebrae (versus 12 or 13). Description. Body shape and pigmentation in Figs. 1 and 2. Morphometric data for examined specimens in Table 1. Largest examined specimen 121.6 mm LEA. Body elongate, distinctly compressed laterally. Greatest body depth at vertical through distal margin of pectoral fin. Dorsal profile of body convex to straight. Ventral profile slightly convex. Caudal filament elongate. Head compressed, greatest width in opercular region and greatest depth at nape (Fig. 2). Dorsal profile of head convex. Ventral profile of head slightly straight. Snout subconical in lateral view. Mouth subterminal. Premaxillary teeth 38(1) or 42 (1) arranged in five (1) or six (1) rows. First premaxillary teeth row mobile, teeth attached only to anteroventral margin of premaxilla. Maxilla slender with short, hook-shaped anterodorsal process. Posterior margin of maxilla reaching posterior margins of first and second infraorbitals. Dentary teeth 31(1) or 38(1) arranged in three (2) rows. Dentary teeth attached in bony dorsolateral flange of dentary (Fig. 3). Coronomeckelian bone corresponds to 45% of length of Meckel���s cartilage. Endopterygoid teeth 10(1) arranged in single row. Mouth rictus extending posteriorly to vertical between nares or on posterior nostril. Anterior naris tube-like, closer to snout tip than to anterior margin of eye. Posterior naris rounded, without tube; near midpoint between anterior naris and anterior margin of eye. Eye small, circular, completely covered by thin membrane, on anterior one-half of HL and laterally oriented. Antorbital and infraorbitals 1 to 4 enlarged, partially cylindrical with slender osseous arches. Fifth and sixth infraorbitals slender and tubular. Depth of posterodorsal expansion on infraorbitals 1+2 equals total length of infraorbitals 1+2. Gill opening limited to posterior margin of opercle and extending above and below pectoral-fin base. Gill rakers tiny and fleshy. Seven (1) gill rakers on first ceratobranchial. Six (2) gill rakers on first infrapharyngobranchial. Upper pharyngeal plate with 10(1) teeth. Lower pharyngeal plate with nine (1) teeth. Branchial membranes joined at isthmus. Branchiostegal rays five (1). First and second branchiostegal rays narrow. Third to fifth branchiostegal rays spatulate. First to fourth branchiostegal rays attached to anterior ceratohyal. Fifth branchiostegal ray attached to posterior ceratohyal. Anus and urogenital papilla adjacent. Position of anus and urogenital papilla shifting through ontogeny from vertical through posterior margin of eye to vertical through middle of eye. Scales small, cycloid, extending from immediately posterior of head to tip of caudal filament. Scales present on mid-dorsal region of body. Scales above lateral line at midbody eight(4), nine(1), ten*(2), or 11(1). Lateral-line scales to vertical through anal-fin terminus 99(1), 100(3), 104(1), 105(2), or 107*(1). Pectoral-fin rays ii,16(7) or ii,17*(1). Three proximal radials. Distal pectoral-fin margin straight. Total anal-fin rays 164(1), 173(1), 177(1), 178*(2), 182(1), or 192(1). Anal-fin origin below pectoral-fin insertion. Distal margin of anal fin straight. First unbranched rays tiny; rays progressively increasing in size to first branched rays. Branched rays all of nearly equal length, except for posterior most rays that progressively decrease in size. Precaudal vertebrae 14*(7). Transitional vertebrae three (3) or four* (4). Vertebrae to end of anal fin 57(1), 59(2), 60(2) or 61(1). Pleural ribs six*(3) or seven (7). Displaced hemal spines four* (7). Coloration in alcohol. Body ground coloration cream. Body densely covered by dark chromatophores gradually more spaced ventrally. Chromatophores more concentrated on perforated scales forming lateral line stripe (Fig. 1). Second layer of pigmentation formed by multiple, small bars of dark chromatophores situated between musculature associated with anal-fin pterygiophores. Dark individual bars in combination form two stripes-like patterns. Inferior midlaterial stripe approximately as wide as orbital diameter. Anal-fin base stripe approximately as wide as orbital diameter. Head densely covered by dark chromatophores gradually more spaced ventrally. Lips distinctly darker than proximate areas. Pectoral and anal fins hyaline with scattered dark chromatophores overlying fin rays. Distribution. Eigenmannia oradens is only known from its type locality in the R��o Ventuari, R��o Orinoco basin, Estado Amazonas in Venezuela (Fig. 4). Etymology. The specific epithet, oradens, is from the Latin ora, meaning edge, and dens, meaning tooth, in allusion to the presence of a bony dorsolateral flange on the dentary in which teeth are attached. An adjective. Remarks. Eigenmannia oradens can be diagnosed among congeners by a remarkable arrangement of the oral dentition. In the premaxilla the anterobasal margin of the first tooth row is attached to it surface. Consequently, this arrangement, gives mobility freedom to the teeth, which can reach 90 degrees from the vertical. This type of attachment is also known in species of Archolaemus (Vari et al., 2012). Broadly, the premaxilla attachment in Archolaemus and E. oradens can be included in the Type 3 of Fink (1981) [���...a tooth attachment mode which acts as a hinge, with its axis of rotation being the anterior tooth attachment site���; pg. 176]. In contrast, the first tooth row is completely attached to the premaxilla in Sternopygidae, Type 2 of Fink (1981). The dentary of E. oradens is characterized by a bony dorsolateral flange, which anchors numerous teeth along its extension (Fig. 3). Such condition also occurs in Archolaemus, D. guchereauae, and Japigny. And according to the current hypotheses of phylogenetic relationships it is considered a convergence among the four taxa (e.g., Tagliacollo et al., 2016). As noted in the diagnosis for the new species, the number of teeth rows of premaxilla and dentary have a large variation across Eigenmannia and can be explored as source of taxonomic characters. The description of E. oradens corroborates with previous studies that used teeth arrangement and attachment as a valuable source of taxonomic information at different hierarchical levels (e.g., Vari et al., 2012; Peixoto et al., 2015; Peixoto & Wosiacki, 2016; Campos-da-Paz & Queiroz, 2017; Dutra et al., 2017; Peixoto & Waltz, 2017). Comparative material examined. Archolaemus blax: INPA 6424, 20+4CS, 118���270mm TL, Rio Tocantins above Tucuru�� Dam, Brazil. MNRJ 12158, 18+4CS of 93, 90.0���382.0 mm TL, Rio Bezerra, Rio Tocantins basin, Brazil. Archolaemus ferreirai: INPA 6422, 8+4CS paratypes, 131.0���269.0 mm TL, Rio Mucaja��, Rio Branco basin, Brazil. INPA 36379, 20+1CS paratype, 119.0���342.0 mm TL, Rio Mucaja��, Rio Branco basin, Brazil. Archolaemus janeae: INPA 36380, 14+2CS paratypes, 136.0���225.0 mm TL, Rio Iriri, Rio Xingu basin, Brazil. Archolaemus luciae: INPA 20964, 8+4CS paratypes, 106.0���200.0 mm TL, Rio Trombetas, Brazil. Archolaemus orientalis: FMNH 94418, 1CS of 3 paratype, Rio S��o Francisco, Brazil. MPEG 21508, holotype, 156.0 mm TL, Rio Paracatu, Rio S��o Francisco basin, Brazil. MPEG 21509, 1MS paratype, 150.0 mm TL, Rio Paracatu, Rio S��o Francisco basin, Brazil. Archolaemus santosi: INPA 36382, 6+3CS paratypes, 73.0���212.0 mm TL, Rio Jamari, Rio Madeira basin, Brazil. Distocyclus conirostris: INPA 11482, 7+3CS of 32, 100.2���197.0 mm LEA, Rio Purus, Brazil. INPA 28879, 2CS of 19, 108.7���165.0 mm LEA, Rio Negro, Brazil. INPA 28915, 2CS of 11, 108.1��� 130.5 mm LEA, Rio Negro, Brazil. INPA 34018, 8+1CS, 132.0��� 174.5 mm LEA, Praia Grande above community of Carapan��, Rio Purus basin, Brazil. MPEG 20023, 2+1CS, 120.9���196.4 mm LEA, Rio Arari, Ilha do Maraj��, Brazil. MPEG 20024, 2+1CS, 149.1���181.0 mm LEA, Rio Arari, Ilha do Maraj��, Brazil. MZUSP 6982, 2+1CS, 156.2���166.0 mm LEA, Rio Madeira, Brazil. Distocyclus guchereauae: MNHN 2003-0013, 1, 222.0 mm TL, Maroni drainage, French Guiana. MNHN 2003-0014, 1, 232.0 mm TL, Maroni drainage, French Guiana. MNHN 2003-0018, 2, 322.0���321.0 mm TL, Maroni drainage, French Guiana. Eigenmannia antonioi: MPEG 10182, 6+1CS paratypes, 77.0��� 118.3 mm LEA, Rio Anapu, Brazil. Eigenmannia besouro: MZUSP 57890, holotype, 91.9 mm LEA, Rio Grande, S��o Desid��rio, Brazil; MZUSP 119104, 5+1CS, paratypes, 69.6���106.1 mm LEA. MZUSP 83792, 6+1CS, paratypes, 55.8���68.8 mm LEA, Rio Preto, Brazil. Eigenmannia desantanai: NUP 3470, 10+1CS paratypes, 119.8��� 142.8 mm LEA, Rio Cuiab��, Brazil. Eigenmannia guairaca: NUP 6467, 8+2CS paratypes, 81.4���135.8 mm LEA, Riacho ��gua do ��, Brazil. Eigenmannia humboldtii: IAvH-P 6788, 1, 316.7 mm LEA, R��o Atrato, Colombia. IAvH-P 6794, 1, 330.0 mm LEA, R��o Atrato, Colombia. IAvH-P 6800, 288.3 mm LEA, R��o Atrato, Colombia. IAvH-P 6806, 1CS, 205.7 mm LEA, R��o Atrato, Colombia. IAvH-P 7024, 1, 199.8 mm LEA, R��o Atrato, Colombia. IAvH-P 7415, 2, 240.9��� 270.1 mm LEA, R��o Atrato, Colombia. IAvH-P 7822, 1, 312.0 mm LEA, R��o Magdalena, Colombia. IAvH-P 7823, 1, 264.0 mm LEA, R��o Magdalena, Colombia. NRM 27741, 1, 294.1 mm LEA, Can�� Ponelaolla, Colombia. USNM 247229, 3, 134.9��� 175.6 mm LEA, R��o Salado, Colombia. Eigenmannia limbata: INPA 18288, 2CS, 98.0���151.0 mm LEA, Lago Mamirau��, Brazil. USNM 305802, 10+2CS, 122.6���250.5 mm LEA, Rio Matos, Bolivia. Eigenmannia macrops: BMNH 1897.8.6.1, holotype, 128.5mm LEA, Potaro River, Guyana. USNM 402684, 6, 80.1���116.8 mm LEA, Cuyuni River, Guyana. USNM 405265, 3, 56.3���107.8 mm LEA, Cuyuni River, Guyana. USNM 405266, 15+1CS, 63.3���162.9 mm LEA, Cuyuni River, Guyana. Eigenmannia matintapereira: MZUSP 109618, 3+1CS paratypes, 79.7���143.6 mm LEA, Rio Uneiuxi, Brazil. MZUSP 109695, 5+1CS paratypes, 65.7���167.7 mm LEA, Rio Urubaxi, Brazil. Eigenmannia meeki: USNM 293171, holotype, 235.7 mm LEA, R��o Pucuro, Panam��. MPEG 33912, 1+1 CS, 194.6���222.0 mm LEA, R��o Pucuro, Panam��. Eigenmannia microstoma: BMNH 1868.7.8.2���3, 2 syntypes, 101.1���139.3 mm LEA, Rio S��o Francisco basin, Brazil. ZMUC P2516 (formally ZMUC 21), 1 syntype (photo and radiograph), 162.8 mm LEA, Rio S��o Francisco basin, Brazil. ZMUC P2517 (formally ZMUC 23), 1 syntype, 153.8 mm LEA, Rio S��o Francisco basin, Brazil. ZMUC P2518 (formally ZMUC 24), 1 syntype, 176.6 mm LEA, Rio S��o Francisco basin, Brazil. ZMUC P2519 (formally ZMUC 25), 1 syntype, 105.1 mm LEA, Rio S��o Francisco basin, Brazil. ZMUC P2520 (formally ZMUC 26), 1 syntype, 101.1 mm LEA, Rio S��o Francisco basin, Brazil. MCP 45216, 5+1CS, 57.7���91.6 mm LEA, Rio Pandeiros, Brazil. Eigenmannia muirapinima: MPEG 21777, 1+3CS paratypes, 84.6���98.5 mm LEA, Lago Jar��, Brazil. MPEG 29489, 11+2CS paratypes, 76.2���97.7 mm LEA, Igarap�� Santo Ant��nio, Brazil. Eigenmannia nigra: ANSP 162130, 3 paratypes, 243.0���265.0 mm LEA, R��o Casiquiare, Venezuela. BMNH 1998.3.17, 8 of 15, 133.0��� 192.9 mm LEA, Paran�� Apara, Brazil. CAS 54387, 3+1CS of 5, 139.2��� 166.9 mm LEA, R��o Orinoco bifurcation, Venezuela. CAS 54518, 1, 130.3 mm LEA, R��o Orinoco bifurcation, Venezuela. INPA 9976, 3+1CS of 10, 149.7��� 223.1 mm LEA, Paran�� Apara, Brazil. INPA 15813, 12, 148.4��� 222.4 mm LEA, Lago Tef��, Brazil. USNM 260240, 4+1CS of 22, 192.2��� 225.2 mm LEA, main channel of R��o Apure, Venezuela. Eigenmannia pavulagem: MPEG 9524, 3CS paratypes, 90.7���108.5 mm LEA, Igarap�� Anuera-Grande, Brazil. MPEG 29490 paratypes, 25+2CS, 26.2���176.6 mm LEA, Igarap�� Paraquequara, Brazil. Eigenmannia sayona: MZUSP 96497, holotype, 131.8 mm LEA, R��o Parguaza, Cede��o, Venezuela; MZUSP 119711, paratypes, 6+2CS, 27.8-116.2 mm LEA. Eigenmannia trilineata: UFRGS 6635, 10, 58.5���143.8 mm LEA, Rio Tramanda��, Brazil. UFRGS 6790, 12, 92.8���159.1 mm LEA, Arroio Gueromana, Brazil. UFRGS 8788, 3, 114.2��� 130.5 mm LEA, Rio Pardo, Brazil. UFRGS 13329, 1, 124.3 mm LEA, Arroio Corrientes, Brazil. Eigenmannia virescens: MCP 12474, 1, 190.1 mm LEA, Rio Uruguai, Brazil. MCP 13416, 5, 148.7���196.0, Rio do Peixe, Brazil. MCP 16797, 5+2CS, 143.7���182.0 mm LEA, Rio Ijuizinho, Brazil. MCP 19330, 1, 147.0 mm LEA, Rio Uruguai, Brazil. MCP 21139, 3, 157.3��� 236.1 mm LEA, Rio das Antas, Brazil. MCP 26819, 1, 212.9 mm LEA, Rio Ibicui, Brazil. Eigenmannia vicentespelaea: MZUSP 83461, 3+1CS, 108.0��� 164.5 mm LEA, Cave of S��o Vicente I, Brazil. Eigenmannia waiwai, INPA 37594, 31+2CS paratypes, 94.0��� 138.1 mm LEA, Rio Mapuera, Brazil. INPA 37567, 3+1CS paratypes, 74.9���154.8 mm LEA, Cachoeira Porteira, Brazil. ��� Eigenmannia ��� goajira: USNM 121596, holotype, 377.0 mm LEA, R��o Socuy, Venezuela. USNM 121596, 1, paratype, 335.6 mm LEA, R��o Socuy, Venezuela. Japigny kirschbaum: MNHN 2008-1201, 110.9 mm TL, holotype, Mana River, French Guiana; MNHN 2000-5954, 2, 99���111 mm TL, paratypes, Maroni drainage, French Guiana. FMNH 50185, 3CS, New River drainage, head of Itabu Creek, Guyana. Rhabdolichops caviceps: INPA 20157, 8+2CS, 108.7���134.5 mm LEA, Paran�� do Xiboquena, tributary of Rio Solim��es, Brazil. Rhabdolichops eastwardi: INPA 12361, 2CS of 41, Lago do Prato, Rio Negro, Amazonas, Brazil. MPEG 1189, 2CS, 115.1���127.8 mm LEA, Rio Goiapi, Ilha do Maraj��, Brazil. Rhabdolichops electrogrammus: INPA 28863, 8+2CS of 79, 96.8��� 101.5 mm LEA, Rio Negro, Brazil. Rhabdolichops lundbergi: INPA 11406, 7+3CS of 111, 133.6��� 155.6 mm LEA, Rio Coari, tributary of Rio Solim��es, Brazil. Rhabdolichops nigrimans: INPA 28862, 11+2CS, 97.3���132.0 mm LEA, Rio Negro, Brazil. Rhabdolichops troscheli: MPEG 1174, 1, Rio Goiapi, Ilha do Maraj��, Brazil. MPEG 2604, 9+2CS, 90.0��� 94.7 mm LEA, Rio Goiapi, Ilha do Maraj��, Brazil. MPEG 2803, 1CS, 222.0 mm LEA, Rio Goiapi, Ilha do Maraj��, Brazil. MPEG 8482, 1CS, 170.1 mm LEA, Tom��-A��u, Par��, Brazil., Published as part of Dutra, Guilherme Moreira, Peixoto, Luiz Ant��nio Wanderley, Santana, Carlos David De & Wosiacki, Wolmar Benjamin, 2018, A new species of Eigenmannia Jordan & Evermann (Teleostei: Gymnotiformes: Sternopygidae) from R��o Ventuari, Venezuela, pp. 132-140 in Zootaxa 4422 (1) on pages 133-138, DOI: 10.11646/zootaxa.4422.1.8, http://zenodo.org/record/1251065, {"references":["Peixoto, L. A. W. & Wosiacki, W. B. (2016) Eigenmannia besouro, a new species of the Eigenmannia trilineata species-group (Gymnotiformes: Sternopygidae) from the rio Sao Francisco basin, northeastern Brazil. Zootaxa, 4126 (2), 262 - 270. https: // doi. org / 10.11646 / zootaxa. 4126.2.6","Campos-da-Paz, R. & Queiroz, I. R. (2017) A new species of Eigenmannia Jordan and Evermann (Gymnotiformes: Sternopygidae) from the upper rio Paraguai basin. Zootaxa, 4216, 73 - 84. https: // doi. org / 10.11646 / zootaxa. 4216.1.5","Dutra, G. M., de Santana, C. D. & Wosiacki, W. B. (2017) A new species of the glass electric knifefish genus Eigenmannia Jordan and Evermann (Teleostei: Gymnotiformes: Sternopygidae) from Rio Tuira Basin, Panama. Copeia, 105, 85 - 91. https: // doi. org / 10.1643 / CI- 16 - 439","Peixoto, L. A. W., Dutra, G. M. & Wosiacki, W. B. (2015) The Electric Glass Knifefishes from the Eigenmannia trilineata species-group (Gymnotiformes: Sternopygidae): monophyly and description of seven new species. Zoological Journal of the Linnean Society, 175, 384 - 414. https: // doi. org / 10.1111 / zoj. 12274","Vari, R. P., de Santana, C. D. & Wosiacki, W. B. (2012) South American eletric knifefishes of the genus Archolaemus (Ostariophysi, Gymnotiformes): undetected diversity in a clade of rheophiles. Zoological Journal of the Linnean Society, 165, 670 - 699. https: // doi. org / 10.1111 / j. 1096 - 3642.2012.00827. x","Fink, W. L. (1981) Ontogeny and phylogeny of tooth attachment modes in Actinopterygian Fishes. Journal of Morphology, 167, 167 - 184. https: // doi. org / 10.1002 / jmor. 1051670203","Peixoto, L. A. W & Waltz, B. T. (2017) A new species of the Eigenmannia trilineata species group from the Rio Orinoco basin, Venezuela (Gymnotiformes: Sternopygidae). Neotropical Ichthyology, 15, e 150199. https: // doi. org / 10.1590 / 1982 - 0224 - 20150199"]}

Eigenmannia 1. Two inconspicuous dark-brown longitudinal stripes on the flank.............................................................. E. virescens 1’. Three or four conspicuous dark-brown longitudinal stripes on the flank.............................................................. 2 2. Premaxilla with nine or 10 teeth distributed in two rows; pectoral fin with ii,11 or 12 rays and anal fin with 151 to 170 rays.............................................................. E. guairaca 2’. Premaxilla with 31 to 33 teeth distributed in four rows; pectoral fin with ii,14 or 15 rays and anal fin with 176 to 217 rays.............................................................. E. trilineata, Published as part of Ota, Renata Rúbia, Deprá, Gabriel de Carvalho, Graça, Weferson Júnio da & Pavanelli, Carla Simone, 2018, Peixes da planície de inundação do alto rio Paraná e áreas adjacentes: revised, annotated and updated, pp. 1-111 in Neotropical Ichthyology 16 (2) on page 59, DOI: 10.1590/1982-0224-20170094, http://zenodo.org/record/3678395

Eigenmannia guairaca Peixoto, Dutra, Wosiacki, 2015 Fig. 17 Body elongated and compressed; greatest body depth contained 5.9 to 7.0 times in TL; head length 6.5 to 8.3, anal-fin base length 0.7 to 1.2, caudal filament length 2.8 to 4.5, preanal distance 5.0 to 6.0 and prepectoral distance 6.1 to 7.7 in LEA; snout length 3.8 to 4.9, horizontal orbital diameter 6.7 to 8.8 and least interorbital width 2.7 to 3.5 in HL. Mouth terminal; premaxilla with 9 or 10 teeth distributed in two rows. Pectoral fin with 12 or 13 rays and anal fin with 151-170 rays. Lateral line complete, with 110- 143 pored scales; transverse series above lateral line with 9-11 scale rows. Ground color pale brown; four dark-brown longitudinal stripes on flank (one superior medial, one lateral line, one inferior medial and one at anal-fin base). Maximum total length. 173.0 mm TL. Distribution. Tributaries of the rio Iguatemi, and riacho Água do Ó, tributary of rio Paranapanema, upper rio Paraná basin. Remarks. Peixoto et al. (2015) reviewed the Eigenmannia trilineata species-group, described the new species, E. guaiaraca, from the riacho Água do Ó, tributary of the rio Paranapanema, upper rio Paraná basin, and restricted the distribution of E. trilineata to the lower rio Paraná basin. Analyzing additional material hosted at Coleção Ictiológica do Nupélia, specimens similar to E. guairaca were found in tributaries of the rio Iguatemi, right bank of the upper rio Paraná, and specimens similar to those redescribed as E. trilineata by Peixoto et al. (2015) in the upper rio Paraná floodplain and some of its tributaries (e.g. rio Paracaí). Therefore, the occurrence of both species in the studied region has been recorded., Published as part of Ota, Renata Rúbia, Deprá, Gabriel de Carvalho, Graça, Weferson Júnio da & Pavanelli, Carla Simone, 2018, Peixes da planície de inundação do alto rio Paraná e áreas adjacentes: revised, annotated and updated, pp. 1-111 in Neotropical Ichthyology 16 (2) on page 59, DOI: 10.1590/1982-0224-20170094, http://zenodo.org/record/3678395, {"references":["Peixoto LAW, Dutra GM, Wosiacki WB. The electric glass knifefishes of the Eigenmannia trilineata species-group (Gymnotiformes: Sternopygidae): monophyly and description of seven new species. Zool J Linn Soc. 2015; 175 (2): 384 - 414."]}

Eigenmannia trilineata López, Castello, 1966 Fig. 17 Body elongated and compressed; greatest body depth contained 4.8 to 5.6 times in TL; head length 7.4 to 9.0, anal-fin base length 1.1 to 1.2, caudal filament length 2.8 to 4.0, preanal distance 5.9 to 7.8 and prepectoral distance 7.0 to 9.1 in LEA; snout length 2.5 to 3.5, horizontal orbital diameter 4.0 to 5.2 and least interorbital width 2.0 to 2.6 in HL. Mouth terminal. Pectoral fin with 16-18 and anal fin with 197-230 rays. Lateral line complete, with 110-122 pored scales. Transversal series above lateral line with 15- 16 scale rows (Campos-da-paz, 1997). Ground color pale brown; four dark-brown longitudinal stripes on flank (one superior medial, one on lateral line, one inferior medial and one at anal-fin base) (Graça, Pavanelli, 2007). Maximum total length. 265.0 mm TL (Graça, Pavanelli, 2007). Distribution. Río Paraná basin., Published as part of Ota, Renata Rúbia, Deprá, Gabriel de Carvalho, Graça, Weferson Júnio da & Pavanelli, Carla Simone, 2018, Peixes da planície de inundação do alto rio Paraná e áreas adjacentes: revised, annotated and updated, pp. 1-111 in Neotropical Ichthyology 16 (2) on page 59, DOI: 10.1590/1982-0224-20170094, http://zenodo.org/record/3678395, {"references":["Campos-da-Paz R. Sistematica e taxonomia dos peixes eletricos das bacias dos rios Paraguai, Parana e Sao Francisco, com notas sobre especies presentes em rios costeiros do leste do Brasil (Teleostei: Ostariophysi: Gymnotiformes). [PhD Thesis]. Sao Paulo, SP: Universidade de Sao Paulo; 1997","Pavanelli CS, Graca WJ, Zawadzki CH, Britski HA, Vidotti AP, Avelino GS, Verissimo S. Fishes from the Corumba Reservoir, Paranaiba River drainage, upper rio Parana basin, State of Goias, Brazil. Check List. 2007; 3 (1): 58 - 64."]}

Eigenmannia virescens (Valenciennes, 1836) Fig. 17 Body elongated and compressed; greatest body depth contained 5.7 to 7.0 times in TL; head length 6.4 to 8.3, anal-fin base length 1.1 to 1.2, caudal filament length 2.6 to 4.9, preanal distance 5.3 to 6.4 and prepectoral distance 6.4 to 9.3 in LEA; snout length 3.1 to 4.4, horizontal orbital diameter 5.4 to 7.3 and least interorbital width 2.9 to 4.0 in HL. Mouth terminal. Pectoral fin with 14 or 17 and anal fin with 186-245 rays. Lateral line complete, with 150-162 pored scales; transverse series above lateral line with 15- 16 scale rows (Campos-da-paz, 1997). Ground color pale brown; two dark-brown longitudinal stripes on flank (one on lateral line, one ventral to it) (Graça, Pavanelli, 2007). Maximum total length. 320.0 mm TL (Graça, Pavanelli, 2007). Distribution. Río Orinoco and río de la Plata basins., Published as part of Ota, Renata Rúbia, Deprá, Gabriel de Carvalho, Graça, Weferson Júnio da & Pavanelli, Carla Simone, 2018, Peixes da planície de inundação do alto rio Paraná e áreas adjacentes: revised, annotated and updated, pp. 1-111 in Neotropical Ichthyology 16 (2) on pages 59-60, DOI: 10.1590/1982-0224-20170094, http://zenodo.org/record/3678395, {"references":["Campos-da-Paz R. Sistematica e taxonomia dos peixes eletricos das bacias dos rios Paraguai, Parana e Sao Francisco, com notas sobre especies presentes em rios costeiros do leste do Brasil (Teleostei: Ostariophysi: Gymnotiformes). [PhD Thesis]. Sao Paulo, SP: Universidade de Sao Paulo; 1997","Pavanelli CS, Graca WJ, Zawadzki CH, Britski HA, Vidotti AP, Avelino GS, Verissimo S. Fishes from the Corumba Reservoir, Paranaiba River drainage, upper rio Parana basin, State of Goias, Brazil. Check List. 2007; 3 (1): 58 - 64."]}

Eigenmannia loretana, new species Figs. 1���6, Table 1 Holotype. MUSM 61210, 135 mm, 120 mm LEA, Peru, Loreto, R��o Pacaya, Lago Tomana, southwest of Iquitos, 5��20���40���S, 74��30���00���W, J. S. Albert & W. G. R. Crampton, 21 Sep. 2002. Paratypes. All from Peru. FMNH 134534, 1, 107 mm, 91 mm LEA, Peru, Loreto, R��o Pacaya, Lago Tomana, 5��17'6.13"S, 74��25'25.80"W, J. S. Albert & W. G. R. Crampton, 21 Sep. 2002; MUSM 61212, 2, 60���98 mm (one specimen missing part of tail), 60���77 mm LEA (one specimen missing part of posterior anal fin), Peru, Loreto, R��o Pacaya, Cocha Yanayacu, 5��16���43���S, 74��55���57���W, J. S. Albert & W. G. R. Crampton, 4 Aug 2000; UF 126165, 1, 115 mm, 84 mm LEA, Peru, Loreto, R��o Pacaya, J. S. Albert & W. Crampton, 19 Sep 2004; FMNH 134535, 2, 1 C&S, 101���102 mm, 71���72 mm LEA, Peru, Loreto, R��o Pacaya, Cocha Yarina, 5��24���37.3���S, 74��30���15.18���W, J. S. Albert & W. G. R. Crampton, 14 May 2003; UF 129250, 1, 101 mm, 70 mm LEA, Peru, Loreto, R��o Pacaya, Cocha Yarina, 5��24���37.3���S, 74��30���15.18���W, J. S. Albert & W. G. R. Crampton, 14 May 2003; UF 114721, 1, 96 mm, 74 mm LEA, Peru, Loreto, R��o Pacaya, Cocha Yanayacu, 5��16���43���S, 74��55���57���W, J. S. Albert & W. G. R. Crampton, 4 Aug 2000. Non-types. All from Peru. UF 114494, 26, 82���113 mm, 61���82 mm LEA, Peru, Loreto, Quedabra 33 km southwest of Iquitos, J. S. Albert & W. G. R. Crampton, 6 Aug. 2000; UF 116557, 2, 93���141 mm, 1 C&S 141 mm, (one specimen missing part of tail), 93���103 mm LEA (one specimen missing part of posterior anal fin), Peru, Maynas, Loreto, Quedabra at km 23 on Iquitos-Nauta Road, J. Albert & W. G. R. Crampton, 27 Mar 2001; ANSP 202364, 12, 103��� 130 mm, 75���94.0 LEA, Peru, Loreto, Cocha Santa Thomas, affluent to R��o Nanay, Iquitos, J. Craig & L. Kim, 21 Aug 2016; ANSP 177759, 132 mm, 99 mm LEA, Mixana Reserve, near Iquitos, Loreto, Peru, 03��52'46"S, 73��29'33"W, J. Albert & W. G. R. Crampton, 0 8 April 2004; AUM 38657, 16, 89���111 mm, 56���80 mm LEA, Peru, Loreto, Cocha Santa Thomas, affluent to R��o Nanay, Iquitos, J. Craig & L. Kim, 21 Aug 2016; MUSM 60215, 39, 56���121 mm (one specimen missing part of tail), 56���88 mm LEA (one specimen missing part of posterior anal fin), Peru, Loreto, Cocha Santa Thomas, affluent to R��o Nanay, Iquitos, 3��47'56.9"S, 73��20'31.02"W, J. Craig & L. Kim, 21 Aug 2016; MUSM 60216, 2 C&S, 117���120 mm Peru, Loreto, Cocha Santa Thomas, affluent to R��o Nanay, Iquitos, 3��47'56.9"S, 73��20'31.02"W, J. Craig & L. Kim, 21 Aug 2016; MUSM 60217, 3 C&S, 118��� 128 mm, Peru, Loreto, Cocha Santa Thomas, affluent to R��o Nanay, Iquitos, 3��47'56.9"S, 73��20'31.02"W, J. Craig & L. Kim, 21 Aug 2016. Diagnosis. Table 2 provides a summary of diagnostic traits among species of the E. trilineata species group. Eigenmannia loretana can be distinguished from all congeners except members of the E. trilineata species group by the presence of a superior medial stripe (vs. absent); from members of the E. humboldtii species group by a relatively small adult body size (vs. large adult body size,> 300 mm); from E. macrops by a relatively small eye (eye diameter less than snout length vs. greater than or equal to snout length); and from E. virescens by a terminal (vs. subterminal) mouth and a smaller adult body size (vs. > 230 mm). Eigenmannia loretana can be distinguished from all other species in the E. trilineata species group by the length of the posterodorsal process of infraorbitals 1+2 (60���75% length of infraorbitals 1+2 vs. 40% in E. besouro and E. correntes; 50% in E. matintapereira, E. meeki, E. trilineata, and E. waiwai; and 100% in E. antonioi, E. desantanai, E. guairaca, E. microstoma, E. muirapinima, E. pavulagem, E. sayona, and E. vicentespelaea). Eigenmannia loretana can be further differentiated from species in the E. trilineata group except E. antonioi and E. pavulagem by its premaxillary dentition, with 11���15 teeth distributed in three rows (vs. eight���10 teeth in two rows in E. muirapinima; nine���10 teeth in two rows in E. guairaca; 16 teeth in three rows in E. microstoma; 17 teeth in three rows in E. sayona; 17���20 teeth in three rows in E. correntes; 18���29 teeth in three to four rows in E. besouro; 22���24 teeth in four rows in E. matintapereira; 24���25 teeth in four rows in E. desantanai; 25���26 teeth in four rows in E. vicentespelaea; 31���33 teeth in four rows in E. trilineata; 35���40 teeth in five rows in E. waiwai; and 30���35 teeth in five to six rows in E. meeki). Eigenmannia loretana can be further distinguished from E. antonioi and E. pavulagem by its endopterygoid dentition, with six to seven teeth distributed in a single row (vs. eight���12 teeth in a single row in E. antonioi and eight to 11 teeth in a single row in E. pavulagem), suborbital depth 28���36% HL (vs. 18���27& HL in E. antonioi and 19���27% HL in E. pavulagem), and by coloration with a uniformly dark brown head and light brown pectoral fins on recently-preserved specimens (vs. darkened dorsal region of head gradually becoming lighter ventrally, and hyaline pectoral fins). Endopterygoid dentition also distinguishes E. loretana from all species in the E. trilineata group except E. correntes and E. guairaca (six to seven teeth distributed in a single row vs. eight to nine teeth in a single row in E. antonioi and E. sayona; eight to 11 teeth in one or two rows in E. pavulagem; nine to 12 teeth in one or two rows in E. matintapereira; 11���16 teeth in one or two rows in E. microstoma; eight to nine teeth in two rows in E. muirapinima; 10���11 teeth in two rows in E. besouro; 10���15 teeth in two rows in E. vicentespelaea; 13���15 teeth in two rows in E. meeki; 14���15 teeth in two rows in E. desantanai; 14���17 teeth in two rows in E. waiwai; and 16���17 teeth in two rows in E. trilineata.). Eigenmannia loretana can be further distinguished from E. correntes and E. guairaca by a total anal-fin rays count of 183���219 (vs. 143���164 in E. correntes and 151���170 in E. guairaca), and the size of dentary teeth increasing after the sixth to seventh tooth (vs. all teeth similar in size). Eigenmannia loretana can be further distinguished from E. guairaca by pectoral-fin rays ii, 13���14 (vs. ii, 11���12), suborbital depth, 28���36% HL (vs. 22���28% HL), orbital diameter, 15.7���23.9% HL (vs. 11.4���15.0% HL), head depth at supraoccipital, 86.8���96.7% HL (vs. 75���86.4% HL). Eigenmannia loretana can be further distinguished from E. correntes by head length, 11.2���12.8% LEA (vs. 13.1���14.9% LEA), snout length, 23.9���30.3% HL (vs. 32.2���35.2% HL), interorbital distance, 33.5���40.7% HL (vs. 25.2���30.1% HL), head depth at supraoccipital, 86.8���96.7% HL (vs. 63.7���70.0% HL), and terminal mouth position (vs. subterminal). Description. Gymnotiform with relatively small adult body size, largest recorded specimen 135 mm. Morphometric data and meristic counts summarized in Table 1. No sexual dimorphism observed. Body elongate and laterally compressed, dorsal profile of body convex from posterior margin of head to vertical through middle of anal fin, then slightly angled downwards until caudal filament at insertion of last anal-fin ray. Ventral surface of body straight from base of posterior margin of head to first anal-fin ray, then slightly concave to end of caudal filament. Greatest body depth at posterior margin of pectoral-fin base. Head short and relatively round. Head mildly compressed laterally; greatest width at opercular region and greatest depth at vertical through supraoccipital. Dorsal profile of head slightly convex, from tip of snout to posterior supraoccipital margin. Ventral profile of head slightly convex from lower lip to branchial opening. Mouth terminal, at or slightly below horizontal line through eye. Lower jaw extending anterior to upper jaw (tip of snout) in some specimens. Premaxillary teeth 11���15 (n=3), distributed in three rows. Rictus at or slightly posterior to vertical line through anterior nostril. Posterior nares closer to eye than tip of snout. Eye circular, covered by skin, located laterally on head, closer to dorsal margin of head than ventral margin. Antorbital and infraorbitals 1���4 partial enlarged cylinders, infraorbitals 5���6 as narrow ossified tubes. Posterodorsal expansion of infraorbitals 1+2 equal to approximately 60���75% of the length on infraorbitals 1+2 (Fig. 2). Suspensorium including opercular series and maxilla illustrated in Fig. 3. Maxilla sickle-shaped with smaller sickle-shaped anterodorsal process; descending blade of maxilla gradually increasing in width posteroventrally. Mandible illustrated in Figs. 3 and 4. Dentary V -shaped, with 17���19 (n=3) teeth, distributed in one to two rows; teeth increasing in size towards rictus after sixth to seventh tooth; robust laterosensory canals present along lateroventral surface. Anguloarticular with narrow process on lateral surface, extending dorsally; small rectangular process on medial surface connecting to Meckel���s cartilage. Coronomeckelian bone roughly 20% length of Meckel���s cartilage. Retroarticular small, roughly rectangular, located at posteroventral margin of anguloarticular. Endopterygoid broadly overlapping quadrate and metapterygoid, roughly triangular, with well-developed ascending process and six to seven conical teeth distributed in a single row on ventral margin. Base of quadrate roughly square in shape extending into pointed triangular shape anterodorsally; quadrate articulating with preopercle and symplectic at base through posteroventral process and notch; circular process extending anteroventrally from base. Metapterygoid similar in shape to quadrate, without posterodorsal process and notch; triangular region pointed posterodorsally. Symplectic elongate and triangular. Preopercle crescent-shaped, with robust laterosensory canal tubes along lateral surface. Interopercle teardrop-shaped, with sharp, pointed posterodorsal expansion. Opercle roughly triangular, dorsal margin convex; opercular ridges present along lateral surface of anterior region; center weakly ossified, becoming increasingly laminar towards distal margins. Subopercle sickle-shaped, tapering posterodorsally, forming concave dorsal profile. Hyomandibula at roughly 100�� to horizontal line through long axis of head; dorsal articulating head roughly one and a half times wider than ventral margin; laminar anterior shelf extending from widest of hyomandibula point to anteroventral margin. Neurocranial bones shown in a full-head CT scan in Fig. 5. Mesethmoid oriented at about 45�� angle from ventral ethmoid, until reaching anterior margin of frontals. Vomer gradually tapering to points laterally near anterior margin of parasphenoid. Paired frontals convex in dorsal profile, roughly half length of total skull length. Supraorbital canal robust, forming a highly ossified shelf-like structure. Entire ventral surface of orbitosphenoid contacting dorsal margin of parasphenoid in adult specimens. Ventral surface of pterosphenoid largely not contacting dorsal margin of parasphenoid, forming lateral fenestrae, varying in size throughout ontogeny. Anterior fontanelle roughly 85% length of posterior fontanelle. Anterior half of posterior fontanelle surrounded by frontals, posterior half by parietals. Prootic and exoccipital with prominent foramenae. Supraoccipital extending dorsally to dorsal margin of parietals. Posttemporal bones fused with supracleithrae. Scales cycloid, present from posterior margin of head to posterior point of caudal filament. Nine to 13 (n=20) longitudinal rows of scales above lateral line. Anal-fin pterygiophore scales small, roughly half the size of other scales. Pectoral-fin rays ii, 13���14 (n=20). Anal-fin origin at or slightly anterior to vertical line through pectoral fin base. Total anal-fin rays 183���219 (n=17). Caudal filament long and cylindrical, occasionally laterally compressed. Precaudal vertebrae 13 (n=3) or 14 (n=2). Displaced haemal spines two (n=1) or three (n=3). Coloration in alcohol. Background color yellowish brown. Head dark brown in recently preserved specimens. Dorsal region of some specimens dark brown, gradually grading into lighter brown/yellow ventrally. Four longitudinal stripes present. Thin, dark lateral line stripe, one scale wide. Superior medial stripe thicker than lateral line stripe, gradually fading out near margin of body cavity. Dark inferior medial stripe and anal-fin base stripes present. Anal fins hyaline, pectoral fins occasionally pigmented in a light brown color. Live Coloration. See Fig. 6. Background color grey-opaque to transparent along body posterior to head. Head covered with chromatophores and colored dark brown. Pectoral fins light brown in some specimens. Four longitudinal stripes present; more apparent than in preserved specimens. Distribution. Collection localities are shown in Figure 7. Known from the Western Amazon in Peru, from the R��o Pacaya and affluents of the R��o Nanay (Fig. 1). Specimens collected over sandy beaches and in floating vegetation along river and stream margins. The type locality was restricted to the R��o Pacaya because of the cryptic nature of species in the E. trilineata complex. Etymology. The new species is named in honor of the residents/inhabitants of Loreto, Peru. Feminine., Published as part of Waltz, Brandon T. & Albert, James S., 2018, New species of glass knifefish Eigenmannia loretana (Gymnotiformes: Sternopygidae) from the Western Amazon, pp. 399-411 in Zootaxa 4399 (3) on pages 401-407, DOI: 10.11646/zootaxa.4399.3.9, http://zenodo.org/record/1206748

Sensory systems encode environmental information that is necessary for adaptive behavioural choices, and thus greatly influence the evolution of animal behaviour and the underlying neural circuits. Here, we evaluate how the quality of sensory information impacts the jamming avoidance response (JAR) in weakly electric fish. To sense their environment, these fish generate an oscillating electric field: the electric organ discharge (EOD). Nearby fish with similar EOD frequencies perform the JAR to increase the difference between their EOD frequencies, i.e. their difference frequency (DF). The fish determines the sign of the DF: when it has a lower frequency (DF > 0), EOD frequency is decreased and vice versa.We study the sensory basis of the JAR in two species:Apteronotus leptorhynchushave a high frequency (ca1000 Hz), spatio-temporally heterogeneous electric field, whereasEigenmanniasp. have a low frequency (ca300 Hz), spatially uniform field. We show that the increased complexity of theApteronotusfield decreases the reliability of sensory cues used to determine the DF. Interestingly,Apteronotusresponds to all JAR stimuli by increasing EOD frequency, having lost the neural pathway that produces JAR-related decreases in EOD frequency. Our results suggest that electric field complexity may have influenced the evolution of the JAR by degrading the related sensory information.

Eigenmannia trilineata Lopez and Castello, 1966 (Sternopygidae) was described from the Rio de La Plata basin and subsequently cited from most South American river basins. Questions about the limits of this species raise the possibility of the occurrence of undescribed species misidentified as E. trilineata. Herein we propose the Eigenmannia trilineata species group for species that share the presence of the superior medial stripe on the flank. This group comprises: Eigenmannia antonioi sp. nov., from the Rio Anapu, Rio Amazonas basin; Eigenmannia desantanai sp. nov., from the Rio Cuiaba, Rio Paraguay basin; Eigenmannia guairaca sp. nov., from the Riacho Agua do O, upper Rio Parana basin; Eigenmannia matintapereira sp. nov., from the Rio Uneiuxi and Rio Urubaxi, Rio Negro basin; Eigenmannia microstoma (Reinhardt, 1852), from the Rio Sao Francisco basin; Eigenmannia muirapinima sp. nov., from small tributaries of the Rio Amazonas; Eigenmannia pavulagem sp. nov., from the tributaries of Rio Capim, Rio Guama basin; E. trilineata, from the lower Rio Parana basin and Rio de La Plata basin; Eigenmannia vicentespelaea Triques, 1996, from Sao Vicente I and II caves, Rio Tocantins basin; and Eigenmannia waiwai sp. nov., from the Rio Trombetas basin. These species can be distinguished from each other by unique sets of meristics, morphometrics, osteological and colour pattern features. © 2015 The Linnean Society of London

Eigenmannia correntes, new species Figures 1���2 Holotype. MNRJ 47046, 113.0 mm LEA, Brazil, Mato Grosso do Sul, Sonora, c��rrego de Baixo, left margin tributary of rio Correntes, at road MS-213, 17o42���46���S 54o21���25���W, R. Campos-da-Paz, 4 Oct 2003. Paratypes. All collected along with holotype. MNRJ 46334, 29, +2 c&s, 14.0���118.0 mm LEA. Non-type material. All from Brazil. MNRJ 46335, 21, 61.0���83.0 mm LEA, Mato Grosso do Sul, Sonora, c��rrego de Cima, left margin tributary of rio Correntes, at road MS-213, 17o39���52���S 54o14���48���W, R. Campos-da- Paz, 4 Oct 2003; MNRJ 46336, 10, 44.0���69.0 mm LEA, Mato Grosso, Itiquira, stream at right margin of rio Correntes, near highway BR-163, 17o28���36���S 54o43���23���W, R. Campos-da-Paz, 5 Oct 2003. Diagnosis. Distinguished from all congeners, except those species included in the Eigenmannia trilineata species-group, by the presence of a conspicuous superior midlateral stripe (Fig. 1; vs. absence). Eigenmannia correntes can be differentiated from all members of the Eigenmannia trilineata species-group, except E. vicentespelaea, E. waiwai and E. besouro, by the mouth subterminal (Fig. 2; vs. terminal in remaining species of the E. trilineata species-group). It differs from E. vicentespelaea by: 1) lower number of premaxillary teeth (17���20, in three irregular rows vs. 25���26, in four rows); 2) lower number of dentary teeth (16���18, in two irregular rows vs. 38���45, in three or four rows); 3) higher number of longitudinal series of scales above lateral line (11���12 vs. 7���8); 4) lower number of pectoral-fin rays (ii,12���13 vs. ii,15���17); 5) lower total number of anal-fin rays (143���164 vs. 169��� 191); 6) larger body width (6.4���8.1% of LEA vs. 3.5���5.8%); and 7) larger oral width (23.5���26.0% of HL vs. 9.5��� 17.2%). It differs from E. waiwai by: 1) larger oral width (23.5���26.0% of HL vs. 9.5���14.6%); 2) longer snout (32.2���35.2% of HL vs. 23.8���31.5%); 3) smaller eye (orbital diameter 10.6���13.3% of HL vs. 22.6���28.8%);) greater postorbital distance (56.8���62.1% of HL vs. 43.9���55.4%); 5) smaller head depth at supraoccipital (63.7���70.0% of HL vs. 73.6���86.2%); 6) longer mouth (19.9���24.6% of HL vs. 12.1���17.7%); 7) lower number of premaxillary teeth (17���20, in three irregular rows vs. 35���40, in five rows); 8) lower number of dentary teeth (16���18, in two irregular rows vs. 37���38, in four rows); 9) higher number of longitudinal series of scales above lateral line (11���12 vs. 9���10); and 10) lower total number of anal-fin rays (143���164 vs. 167���195). Finally, it is distinguished from E. besouro by: 1) larger oral width (23.5���26.0% of HL vs. 9.5���19.1%); 2) longer snout (32.2���35.2% of HL vs. 23.7���31.9%); 3) larger eye (orbital diameter 10.6���13.3% of HL vs. 16.9���25.1%); 4) shorter postorbital length (56.8���62.1% of HL vs. 46.9���55.9%); 5) greater suborbital depth (25.2���32.3% of HL vs. 18.3���24.8%); and 6) higher number of longitudinal series of scales above lateral line (11���12 vs.7���10). Description. Morphometric and meristic data of holotype and paratypes summarized in Table 1. Body compressed, more markedly posterior to abdominal cavity and to posterior half of TL. Greatest body depth at abdominal region, near vertical through tip of pectoral fin. Dorsal profile of body nearly straight to gently convex anteriorly; ventral profile slightly convex. Head compressed, widest at opercular region and deepest at occiput. Dorsal profile of head convex from tip of snout to vertical through opercular opening; ventral profile of head slightly concave from tip of mandible to opercular opening. Snout elongate, subconical; eyes of moderate size, circular, covered with thin skin, laterally oriented on anterior third of head length. Mouth of moderate size and subterminal, upper jaw projected, mandible included, rictus near a vertical through posterior naris; teeth present on both jaws, premaxillary and dentary teeth similar in size on each bone. Anterior nares small, tubular, on anterior half of mouth length and close to tip of snout; posterior nares not tubular, elliptical, near a vertical through rictus, about one eye diameter from anterior eye margin. Opercular (branchial) opening of moderate size, immediately anterior to pectoral fin origin, with membranous margin; branchial membranes joined to isthmus. Anus and well-developed urogenital papilla adjacent, ventral to opercular region, with no apparent significant shifting anteriorly with age. Pectoral fin elongate, ellipsoid, with ii,12(9) or ii,13(1) [ii,12] (total pectoral-fin rays, 14���15 [14]). Scales cycloid, present over body posterior from head, including postcranial portion of body and mid-dorsal region, maximum number of scales above lateral line at mid-body 11(4) or 12(6) [11]. Lateral line scales usually larger than those immediately dorsal and ventral to that series, 100���116 [100] to vertical to posterior end of anal fin. Anal-fin origin slightly posterior from vertical through pectoral-fin origin; anterior unbranched anal-fin rays 11���16 [11], less developed and smaller than posterior branched ones; total anal-fin rays 143���164 [143] rays. Tail cylindrical, elongate, tapering to pointed posterior end. Relevant osteological features of Eigenmannia correntes as follows: vomer arrow-shaped anteriorly; lateral ethmoids and nasals present; antorbital and infraorbitals 1���4 enlarged, partial cylinders, with laminar bony arches, fifth and sixth infraorbitals slender and tubular; antorbital 25���30% of total length of infraorbital bones 1+2; infraorbital bones 1+2 with enlarged posterodorsal expansion (depth of posterodorsal expansion [DPE] 40% of length of infraorbital bones 1+2 [LIB]); infraorbitals 3 and 4 closely associated; premaxilla somewhat circular, with 17���20 pointed conical teeth of similar size in three irregular rows (N=2); maxilla edentulous, slender and gently curved posteriorly, with well-developed sickle-shaped anterodorsal process (about 20% of total length of maxilla, equal to width of posterior nostril); dentary triangular, with 16���18 pointed conical teeth of similar size, vertically directed in two irregular rows (N=2); small triangular coronomeckelian bone associated to posterodorsal margin of Meckel���s cartilage, about 20% of Meckel���s cartilage length; endopterygoid with well-developed dorsally directed process; small, pointed, conical teeth located ventrally sometimes in two irregular rows at anterior margin of endopterygoid, 4���5 (smaller, regenerated, c&s specimen) and 8���9 (larger c&s specimen, 112.0 mm LEA); five small elongate basibranchials, the two posterior ones unossified; five hypobranchials, the two posterior ones unossified; epibranchials 1���5 ossified; lower pharyngeal tooth plate with 7���12 conical teeth (N=2); infrapharyngobranchials 1���4 ossified; upper pharyngeal tooth plate with 7 conical teeth (N=2); urohyal broad, with irregular arrow-shaped head and well-developed posterior laminar portion, slightly larger than longest branchiostegal ray; five branchiostegal rays, three anterior ones filamentous, two posterior ones triangular, laminar distally. Scapular foramen present. Three independent pectoral proximal radials, proximal three and four coossified. Fourteen precaudal vertebrae, 10 anterior and 4 transitional vertebrae (N=2); 60 total vertebrae up to the end of anal fin (n=1). Anal pterygiophores slender and thin. Coloration in alcohol. Background colour yellowish pale brown, darker dorsally, lighter ventrally below superior midlateral stripe. Dorsal region of head, opercle area and middorsum brown. Eyes dark. Four longitudinal dark stripes along body: lateral-line stripe, thin, extending from anteriormost perforated lateral-line scales to posterior region of caudal filament, darker and conspicuous posterior from abdominal region; superior midlateral stripe, thicker (2���3 scales deep anteriorly), dark and conspicuous, extending posteriorly from abdominal region;inferior midlateral stripe, thick, extending from postero-ventral region of abdominal region; anal-fin base stripe, moderately thick, extending along anal-fin base. Area between superior midlateral stripe and inferior midlateral stripe light. Pectoral and anal fins hyaline, with scattered chromatophores over rays, interradial membranes hyaline. Caudal filament uniform brown. Geographic distribution. Eigenmannia correntes is currently known only from three streams, all tributaries of the rio Correntes, a major tributary of the rio Piquiri system, upper rio Paraguai basin: c��rrego de Baixo (typelocality; Fig. 3) and c��rrego de Cima (both left margin tributaries, municipality of Sonora, Mato Grosso do Sul state, Brazil); and another stream (not named, at the right margin of the rio Correntes, Itiquira, Mato Grosso, Brazil). To date, the only remaning valid species belonging to the Eigenmannia trilineata species-group recorded in the rio Paraguai basin is E. desantanai (see Peixoto et al., 2015; Fig. 4). Eigenmannia correntes is readily separated from E. desantanai, for instance, for its conspicuous subterminal mouth (vs. terminal in this latter species), premaxilla with 17���20 teeth in three irregular rows (vs. 24���25 teeth in four rows), endopterygoid with 4��� 9 teeth in two irregular rows (vs. 14���15 teeth in two rows), anterior vertebrae 10 (vs. 9), transitional vertebrae 4 (vs. 2���3), precaudal vertebrae 14 (vs. 11���12), 143���164 anal-fin rays (vs. 170���198), and oral width 23.5���26.0% of HL (vs. 13.1���18.4%). Specimens in museum and other institutional collections, usually referred to as E. virescens, are also frequently recorded from the rio Paraguai basin (e.g., Britski et al., 1999), but their actual taxonomic identity needs to be properly addressed. Remarks. Eigenmannia is currently poorly defined within the Sternopygidae, and there is no objective evidence unequivocally demonstrating its monophyly (see ���Introduction���, above). For this reason, E. correntes is herein referred to that genus on the basis of a combination of characters either plesiomorphic or of uncertain polarity (e.g., Tagliacollo et al., 2016): eyes covered by skin; scales present over entire postcranial portion of body; nasal capsule length equal to at least two diameters of the posterior nostril; teeth present posteriorly beyond the anterior portion of the dentary; teeth absent from oral valve; teeth present on endopterygoid; infraorbital bones 1+2 with enlarged posterodorsal expansion; 8) gill rakers short, unossified; and absence of any dark and clear alternating wide vertical bands on body. Giora and Fialho (2009) studied the reproductive biology of, E. trilineata, from southern Brazil, and their results showed a high frequency of mature females from October to February, indicated that the first maturation size estimated for females was 80.5 mm TL, and that the species showed multiple spawining type. Some females of Eigenmannia correntes (individuals collected in October 2003 in the rio Correntes system,> ca. 80.0 mm TL), exhibited conspicuous distended bellies, with translucent/whitish (diameter 1.0 mm, dark yellow/orange coloration), clearly visible inside their abdomen through transparency (Fig. 5) what, as with E. trilineata, suggests a multiple spawning type. Kirschbaum (1979), for instance, also reported multiple spawning type regarding specimens identified by him as E. virescens. Three specimens of Eigenmannia correntes (MNRJ 46335 [01, ca. 65.0 mm LEA, tail broken] and MNRJ 46336 [02, 40.0 mm and 63.0 mm LEA) had cysts containing parasites (probably metacercariae; M. M. Ishikawa and S. B. de P��dua, pers. comm.), apparently representing the first evidence of this kind of parasitism in the genus (Fig. 6). Etymology. The specific epithet correntes refers to the rio Correntes, the main river at the rio Piquiri system, upper rio Paraguai basin, from where all specimens used in the original description were collected. A noun in apposition. Comparative material. Eigenmannia microstoma: ZMUC [���Jrn. 24���], 1, syntype, Brazil, Minas Gerais, Lagoa Santa; MNRJ 24494, 3, Brazil, Alagoas, Penedo; MZUSP 22955, 2, Brazil, Minas Gerais, Tr��s Marias, rio S��o Francisco; MZUSP 24643, 1 c&s, Brazil, Tr��s Marias, Tr��s Marias dam; Eigenmannia trilineata: MZUSP 22616.0, 1, Argentina, Buenos Aires, Rio de La Plata; Eigenmannia vicentespelaea: MZUSP 42605, 1, holotype, Brazil, Goi��s, S��o Domingos, Caverna (��� cave ���) S��o Vicente II, rio Tocantins basin; MZUSP 47984, 1 paratype, collected along with holotype; Eigenmannia matintapereira: MZUSP 29973, 1, paratype, Brazil, Amazonas, rio Arirar��; MZUSP 29974, 1, paratype, Brazil, Amazonas, rio Maraui��, rio Negro basin; MZUSP 29975, 3, Brazil, Amazonas, rio Negro; MZUSP 29981, 1, Brazil, Amazonas, rio Negro., Published as part of Campos-Da-Paz, Ricardo & Queiroz, Igor Raposo, 2017, A new species of Eigenmannia Jordan and Evermann (Gymnotiformes: Sternopygidae) from the upper rio Paraguai basin, pp. 73-84 in Zootaxa 4216 (1) on pages 76-82, DOI: 10.5281/zenodo.229831, {"references":["Peixoto, L. A. W., Dutra, G. M. & Wosiacki, W. B. (2015) The electric glass knifefishes of the Eigenmannia trilineata speciesgroup (Gymnotiformes: Sternopygidae): monophyly and description of seven new species. Zoological Journal of the Linnean Society, 175, 384 - 414. http: // dx. doi. org / 10.1111 / zoj. 12274","Britski, H. A., de Silimon, K. Z. & Lopes, B. S. (1999) Peixes do Pantanal. Manual de identificacao. Embrapa-SPI, Brasilia, 184 pp.","Tagliacollo, V. A., Bernt, M. J., Craig, J. M., Oliveira, C. & Albert, J. S. (2016) Model-based total evidence phylogeny of Neotropical electric knifefishes (Teleostei, Gymnotiformes). Molecular Phylogenetics and Evolution, 95, 20 - 33. http: // dx. doi. org / 10.1016 / j. ympev. 2015.11.007","Giora, J & Fialho, C. B. (2009) Reproductive biology of weakly electric fish Eigenmannia trilineata Lopez and Castello, 1966 (Teleostei, Sternopygidae). Brazilian Archives of Biology and Technolology, 52, 617 - 628. http: // dx. doi. org / 10.1590 / S 1516 - 89132009000300014","Kirschbaum, F. (1979) Reproduction of the weakly electric fish Eigenmannia virescens (Rhamphichthyidae, Teleostei) in captivity. I. Control of gonadal recrudescence and regression by environmental factors. Behavioral Ecology and Sciobiology, 4, 331 - 355. http: // dx. doi. org / 10.1007 / BF 00303241"]}

Regulating membrane potential and synaptic function contributes significantly to the energetic costs of brain signaling, but the relative costs of action potentials (APs) and synaptic transmission during high-frequency firing are unknown. The continuous high-frequency (200-600Hz) electric organ discharge (EOD) of Eigenmannia, a weakly electric fish, underlies its electrosensing and communication. EODs reflect APs fired by the muscle-derived electrocytes of the electric organ (EO). Cholinergic synapses at the excitable posterior membranes of the elongated electrocytes control AP frequency. Based on whole-fish O2 consumption, ATP demand per EOD-linked AP increases exponentially with AP frequency. Continual EOD-AP generation implies first, that ion homeostatic processes reliably counteract any dissipation of posterior membrane ENa and EK and second that high frequency synaptic activation is reliably supported. Both of these processes require energy. To facilitate an exploration of the expected energy demands of each, we modify a previous excitability model and include synaptic currents able to drive APs at frequencies as high as 600 Hz. Synaptic stimuli are modeled as pulsatile cation conductance changes, with or without a small (sustained) background conductance. Over the full species range of EOD frequencies (200-600 Hz) we calculate frequency-dependent "Na+-entry budgets" for an electrocyte AP as a surrogate for required 3Na+/2K+-ATPase activity. We find that the cost per AP of maintaining constant-amplitude APs increases nonlinearly with frequency, whereas the cost per AP for synaptic input current is essentially constant. This predicts that Na+ channel density should correlate positively with EOD frequency, whereas AChR density should be the same across fish. Importantly, calculated costs (inferred from Na+-entry through Nav and ACh channels) for electrocyte APs as frequencies rise are much less than expected from published whole-fish EOD-linked O2 consumption. For APs at increasingly high frequencies, we suggest that EOD-related costs external to electrocytes (including packaging of synaptic transmitter) substantially exceed the direct cost of electrocyte ion homeostasis.

Made available in DSpace on 2018-11-26T17:41:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-10-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) CONICYT, BECAS-CHILE The cytogenetic characteristics of Eigenmannia aff. trilineata were analyzed by basic and molecular cytogenetics, applying fluorescent in situ hybridization, with 18S and 5S rDNA and U2 snRNA probes. The species revealed a kind of polymorphism associated to ZZ/Z0 type sex chromosomes, with 2n=32 (8m+2sm+22a, NF=42) in all males under analysis, whereas females evidenced 2n=31 (8m+1sm+22a, NF=40). C-banding showed constitutive heterochromatin restricted to the pericentromeric region of all chromosomes and single-nucleolus organized regions on pair 11. A site for rDNA 5S was synthetic with a cluster of rDNA 18S near the centromere on the long arm of only one homologue of pair 11. Other clusters for 5S rDNA were sited on pairs 7, 10, 12, 13, and 16. Further, 5S rDNA was co-located with U2 cluster in the pericentromeric region of pair 12. Joint analysis of DNA barcoding from cytochrome c oxidase subunit I (COI) sequences, generated from the karyotyped samples of E. aff. trilineata, and sequences of other Gymnotiforms recognized E. aff. trilineata as an Operational Taxonomic Unit. Results foreground the hypothesis that cytotypes are independent evolution units as cryptic species with a low morphological differentiation level, although with high genetic/karyotype differentiation rates. Univ Estadual Paulista, Dept Morphol, Inst Biosci, Dist Rubiao Jr S-N, BR-18618970 Botucatu, SP, Brazil Univ Estadual Paulista, Dept Morphol, Inst Biosci, Dist Rubiao Jr S-N, BR-18618970 Botucatu, SP, Brazil CONICYT, BECAS-CHILE: 72110694

The weakly electric knifefish Eigenmannia emits an electric organ discharge (EOD) of constant frequency and sinusoidal waveform that varies with sex and age. Eigenmannia discriminates among these except when stimulated at the same frequency as its own EOD frequency. In that case, it needs to perform a Jamming Avoidance Response (frequency shift) which results in a beating mixed signal. By a sophisticated analysis of the amplitude and phase modulations of the beat signal, Eigenmannia derives the frequency difference, its sign, and the waveform of the stimulus, hence the signaller’s identity. The human ear is not capable of an equivalent waveform analysis of acoustic stimuli.

Eigenmannia besouro, new species (Figure 1) Holotype. MZUSP 57890, 91.9 mm LEA, Brazil, Bahia, S��o Desid��rio, S��tio Grande, rio S��o Francisco basin, rio Grande, 12 �� 25 ' 40.09 "S 45 ��05' 10 "W, O. Oyakawa, A. Akama & V. Garutti, 8 Jul 1998. Paratypes. All from rio S��o Francisco basin, Brazil. Bahia: MZUSP 57889, 3, 94.6���105.4 mm LEA, S��o Desid��rio, rio S��o Desid��rio, O. Oyakawa, A. Akama & V. Garutti, 7 Jul 1998; MZUSP 57895, 1, 117.93 mm LEA, Formosa do Rio Preto, rio Preto, 11 �� 3 ' 15 "S 45 �� 12 ' 6 "W, O. Oyakawa, A. Akama & V. Garutti, 3 Jul 1998. MZUSP 83792, 6+ 1 CS, 55.8���68.8 mm LEA, Formosa do Rio Preto, rio Preto, 11 �� 8 ' 28 "S 46 �� 4 ' 1 "W, C. Moreira & J. Nolasco, 15 Nov 2002; MZUSP 84036, 7, 44.3���61.3 mm LEA, Formosa do Rio Preto, rio Preto, 11 �� 8 ' 28 "S 46 �� 4 ' 1 "W, C. Moreira, J. Nolasco & M. Avila, 3 Aug 2002; MZUSP 84070, 6, 13.9���100.1 mm LEA, Formosa do Rio Preto, rio Sap��o, tributary to rio Preto, 10 �� 55 ' 39 "S 45 �� 41 ' 54 "W, C. Moreira & J. Nolasco, 6 Aug 2002; MZUSP 84113, 1, 75.9 mm LEA, Formosa do Rio Preto, rio Preto, 11 �� 2 ' 59 "S 45 �� 11 ' 31 "W, C. Moreira & J. Nolasco, 20 Nov 2002; MZUSP 98748, 2, 65.6 ���81.0 mm LEA, Barra, rio Grande, 11 �� 6 ' 8 "S 43 �� 9 ' 26 "W, O. Oyakawa, A. Akama, V. Garutti & J. Nolasco, 10 Apr 2001; MZUSP 114281, 1, 80.6 mm LEA, Lu��s Eduardo Magalh��es, rio Veredinha, rio Grande, 11 �� 10 ' 1.5 "S 44 �� 17 ' 9.3 "W, J. Birindelli, F. Dagosta, M. Loeb & C. Santos, 4 Dez 2012; MZUSP 114520, 2, 10.9���26.8 mm LEA, S��o Desid��rio, rio Galheir��o, rio Grande, 12 �� 29 ' 29.3 "S 45 �� 12 ' 7.2 "W, O. Oyakawa, A. Zanata, P. Camelier & M. Melo, 4 Dec 2012; MZUSP 115398, 1, 50.3 mm LEA, Barreiras, rio de Ondas, 12 �� 7 '37.00"S 45 �� 8 ' 18 "W, O. Oyakawa, A. Zanata, P. Camelier & M. Melo, 3 Dec 2012; MZUSP 119104, 5 + 1 CS, 69.6���106.1 mm LEA; MPEG 33920, 1, 87.9 mm LEA, same data as the holotype. MPEG 33919, 1 CS, 86.0 mm LEA, Formosa do Rio Preto, rio Sap��o, tributary to rio Preto, 10 �� 55 ' 39 "S 45 �� 41 ' 54 "W, C. Moreira & J. Nolasco, 6 Aug 2002. MPEG 33921, 1, 93.2 mm LEA, S��o Desid��rio, rio S��o Desid��rio, O. Oyakawa, A. Akama & V. Garutti, 7 Jul 1998. Diagnosis. Eigenmannia besouro can be distinguished from its congeners, except species of the Eigenmannia trilineata species-group, by the presence of the superior midlateral stripe (vs. absence). Eigenmannia besouro differs from species of the Eigenmannia trilineata species-group, except E. vicentespelaea and E. waiwai, by the subterminal mouth (vs. terminal). Eigenmannia besouro can be further differentiated from the striped species of Eigenmannia, except E. vicentespelaea, by the more anterior origin of the superior midlateral stripe, at vertical between base of 5 th to 15 th anal-fin ray in specimens larger than 65 mm LEA (vs. origin at vertical between 18 th to 35 th anal-fin ray). Eigenmannia besouro can be differentiated from E. vicentespelaea by: the number of pectoral-fin rays, ii, 13���14 (vs. ii, 15���17); the dentition pattern of dentary, 19���30 teeth distributed in two or three rows [outermost row with 7���14 teeth; median row with nine; innermost row with 7���13 teeth] (vs. 38���45 distributed in three or four rows [outermost row with 12���21 teeth; the second row with 14���16 teeth; the third row with ten teeth; the innermost row with 2���10 teeth]); and the depth of posterodorsal expansion on infraorbitals 1 + 2 less than 40 % of the length of infraorbitals 1 + 2 (Fig. 2) (vs. corresponds approximately to total length of infraorbitals 1 + 2). Eigenmannia besouro is distinguished from E. waiwai by: the anterodorsal process of the maxilla equal to the width of the posterior nostril (Fig. 3 a) (vs. equal to 1.5 times of the width of the posterior nostril; Fig. 3 b); the anterodorsal process of the premaxilla abruptly directed anteroventrally (Fig. 3 a) (vs. by the anterodorsal process of the premaxilla gradually directed anteroventrally; Fig. 3 b); the dentition pattern of the premaxilla, 18���29 teeth distributed in three or four rows [outermost row with 4���10 teeth; second row with 5���11 teeth; third row with 6���8 row; innermost row with six teeth] (Fig. 4) (vs. 35���40 distributed in five rows [outermost row with 4���10 teeth; second row with seven or eight teeth; third row with eight or nine teeth; fourth row with 7���9 teeth; innermost row with six teeth]); and the dentition pattern of the dentary, 19���30 teeth distributed in two or three rows [outermost row with 7���14 teeth; median row with nine; innermost row with 7���13 teeth] (vs. 37���38 distributed in four rows [outermost row with seven teeth; second row with 11���15 teeth; third row with 8���15; innermost row with 4���8 teeth]). Description. Species of medium size for Eigenmannia, maximum length 147.6 mm TL. Morphometric data in Table 1. Body elongate and laterally compressed. Dorsal profile of body nearly straight from rear of head to vertical through middle of anal fin, and then posteroventrally aligned to distal portion of caudal filament. Ventral profile of body slightly concave along anterior half of abdominal cavity; then posterodorsally aligned to last analfin ray. Ventral profile of caudal filament straight. Greatest body depth at vertical through pectoral-fin distal margin. Head laterally compressed, greatest width at opercular region and greatest depth at posteior margin of supraoccipital. Dorsal profile of head convex from upper lip to vertical through branchial opening. Ventral profile of head slightly concave from anterior margin of lower lip to branchial opening. Snout rounded in lateral profile. Mouth subterminal. Upper lip slightly overlapping lower lip. Premaxilla teeth, 18 (1) 21 (1) or 29 (1) in three or four rows [outermost row with 4 (1), 6 (1) or 10 (1) teeth; second row with 5 (2) or 11 (1); third row with 6 (1), 7 (1) or 8 (1) teeth; innermost row with 6 (1) teeth]. Maxilla with sickle-shaped anterodorsal process equal to width of posterior nostril. Dentary teeth, 19 (1), 23 (1) or 30 (1) in two or three rows [outermost row with 7 (1), 10 (1) or 14 (1) teeth; median row teeth, 9 (1); innermost row teeth, 7 (1), 12 (1) or 13 (1)]. Dentary teeth similar in size. Coronomeckelian bone equal to 30 % of Meckel���s cartilage length. Endopterygoid teeth, 10 (1) or 11 (2) in two rows. Mouth rictus at vertical through anterior nostril or in region between nares. Anterior naris tube-like, posterior margin at vertical through posterior margin or in median portion of rictus. Posterior nares elliptical, without tube, closer to anterior margin of eye than snout tip. Eye approximately circular, covered by skin, positioned laterally on anterior half of head. Antorbital and infraorbitals 1���4 as enlarged, partial cylinders with slender bony arches. Fifth and sixth infraorbitals slender and tubular. Depth of posterodorsal expansion on infraorbitals 1 + 2 equals 40 % of length of infraorbitals 1 + 2. Branchial opening moderately elongate. Branchial membrane joined to isthmus. Anus and urogenital papilla shifting anteriorly ontogenetically. Anus and urogenital papilla at vertical through posterior margin of orbit in mature specimens. Holotype Min Max Mean SD N Total length (mm) 127.0 70.5 147.6 ��� ��� 20 Length to end of anal fin (mm) 91.9 49.4 106.1 ��� ��� 20 Head length (mm) 12.9 7.7 13.7 ��� ��� 20 Percentage of LEA Head length 14.0 12.5 15.6 14.0 0.8 20 Preanal distance 18.8 16.3 19.4 18.0 0.8 20 Prepectoral distance 14.7 14.1 16.4 15.1 0.6 20 Snout to anus 8.6 6.1 13.1 9.2 2.1 20 Body depth at pectoral fin 17.9 13.6 17.9 15.1 0.9 20 Body depth at anal fin 15.8 13.0 16.1 14.4 0.8 20 Body width 6.2 5.2 7.5 6.2 0.6 20 Anal-fin length 82.1 79.3 87.0 83.6 2.1 20 Pectoral-fin length 10.3 8.1 11.0 10.0 0.7 20 Caudal filament length 36.3 26.7 53.8 41.9 6.7 20 Caudal filament depth 1.6 0.6 2.1 1.3 0.4 20 Caudal filament width 0.8 0.4 1.0 0.6 0.1 20 Pecentage of HL Snout length 26.7 23.7 31.9 28.0 2.2 20 Internasal distance 8.2 6.0 10.5 8.4 1.0 20 Snout to posterior naris distance 16.9 16.9 23.4 20.3 1.7 20 Posterior naris to orbit distance 7.4 4.4 9.2 6.6 1.1 20 Internarial width 15.5 10.7 22.6 14.6 2.3 20 Orbital diameter 24.6 16.9 25.1 20.5 2.3 20 Postorbital distance 54.5 46.9 55.9 50.8 2.5 20 Opercular opening 28.8 20.1 29.1 25.2 2.6 20 Suborbital depth 23.2 18.3 24.8 22.3 1.7 20 Interorbital distance 29.8 25.6 38.6 31.5 3.6 20 Head width at opercle 53.4 50.3 67.0 56.3 3.9 20 Head width at orbits 45.1 30.6 50.1 40.6 4.9 20 Head depth at supraoccipital 74.7 67.0 80.9 74.2 3.4 20 Head depth at orbits 56.6 49.8 59.5 55.0 3.1 20 Maxilla length 18.4 14.3 23.8 19.0 2.8 20 Oral width 16.1 9.5 19.1 13.4 2.6 20 Cycloid scales from immediately posterior to head to distal portion of caudal filament. Lateral line complete, 96 (1), 98 (3), 99 (1), 100 (1), 101 (1), 102 *(2), 104 (1), 105 (1), 107 (1), 110 (1), 111 (1), 113 (2), 114 (1), 116 (2), 118 (1) or 120 (1) perforated scales to vertical through end of anal fin. Longitudinal series of scales above lateral line at midbody, 7 (4), 8 *(12), 9 (3) or 10 (1). Scales over anal-fin pterygiophores approximately half size of others. Pectoral-fin rays, ii, 13 (6) or ii, 14 *(15); distal margin slightly rounded; tip reaching vertical through 20 th to 25 th anal-fin rays. Anal-fin origin posterior to vertical through pectoral-fin base; total anal-fin rays, 1 50���181 [168 *] (N= 21); distal margin of anal fin slightly convex. Caudal filament cylindrical, tapering gradually distally, moderate size, approximately 45 % of LEA in mature specimens. Precaudal vertebrae, 14 (3). Anterior vertebrae, 11 (2) or 12 (1), transitional vertebrae, 2 (1) or 3 (2). Displaced hemal spines, 3 (3). Coloration in alcohol. Background color dark brown. Dorsal region of head dark brown; gradually becoming lighter ventrally. Lips and suborbital region light brown. Dorsal region of body dark brown, gradually lighter in region overlying anal-fin pterygiophores. Four longitudinal dark stripes along body. Lateral-line stripe thin, one or two scales deep, extending from first perforated lateral-line scale to distal portion of caudal filament. Superior midlateral stripe thick, two or three scales deep, tapering from vertical between base of 5 th to 15 th anal-fin ray to posterior two-thirds of body in specimens over 65 mm LEA; or tapering from vertical between base of 25 th to 36 th anal-fin ray to posterior two-thirds of body in specimens up to 60 mm LEA. Inferior midlateral stripe moderately thick, two or three scales deep, extending from vertical between base of 15 th to 28 th anal-fin ray to posterior onethird of body. Anal-fin base stripe thick, two scales deep, extending from vertical between base of first and 26 th anal-fin ray to last anal-fin ray. Pectoral and anal fins hyaline, with scattered tiny chromatophores on interradial membranes. Remarks. Recently, Peixoto et al. (2015) redescribed E. microstoma and recorded the rio S��o Francisco basin as its range, the same hydrographic basin of E. besouro. Aiming to clarify the differences between the two species, some diagnostic characters are presented. Eigenmannia besouro differs from E. miscrostoma by: mouth subterminal (vs. terminal); suborbital depth, 18.3���24.8 % HL (vs. 29.9���40.8 %); number of scale series above lateral line, 7���10 (vs. 11-15); depth of the posterodorsal expansion on infraorbitals 1 + 2 less than 40 % of the length of infraorbitals 1 + 2 (vs. approximately equal to the total length of infraorbitals 1 + 2); and length of the coronomeckelian bone equivalent to 30 % of the length of Meckel���s cartilage (vs. equals 45 % of the length of Meckel���s cartilage). Distribution. Eigenmannia besouro is known from tributaries of the left margin of rio S��o Francisco, Bahia, northeastern Brazil (Fig. 5). Etymology. The species name, besouro (���beetle��� in Portuguese) is in honor of Manoel Henrique Pereira, known as Besouro Mangang�� (���The Mangang�� Beetle���), a native of the Rec��ncavo region of Bahia, and a legendary figure in the Afro-Brazilian martial art capoeira; a noun in opposition. Discussion. Given the absence of proposed synapomorphies for Eigenmannia (Mago-Leccia, 1994; Albert & Campos-da-Paz, 1998; Albert, 2001), we consider it more appropriate to assign E. besouro provisionally as a member of this genus because it does not have most of the synapomorphies present in the remaining genera of Eigenmaniinae. Vari et al. (2012) proposed six synapomorphies for Japigny: (1) color pattern composed by alternating dark bands; (2) presence of single row teeth at the base of the upper oral valve; (3) lateral process of the parapophysis of the second vertebrae ventrally curved; (4) distinct separation of the lateral process of the second vertebrae from the parapophysis of the fourth vertebrae; (5) lateral process of the parapophysis of the fourth vertebrae ventrally curved; and (6) retroarticular not included in the socket of the lower jaw with the quadrate. In Eigenmannia besouro, the color pattern is composed of four longitudinal dark stripes without alternating dark bands on flanks. Additionally, the single row of teeth at the base of the upper oral valve is absent, the contact of the lateral process of the second vertebrae with the parapophysis of the fourth vertebrae is present, and the retroarticular is included in the socket of the lower jaw with the quadrate, distinct from the states described by Vari et al. (2012) for Japigny. These features argue against the inclusion of the new species in Japigny. However, the ventral curvature of the lateral process of the parapophysis of the second and fourth vertebrae is present in E. besouro, as well as in most genera of the Eigenmanniinae, and may represent a plesimorphic condition in the subfamily. In the same study, Vari et al. (2012) proposed four synapomorphies for Archolaemus: (1) a free orbital rim; (2) anterobasal margins of the teeth of the first tooth row attached to the dentigerous surface of the premaxilla; (3) pronounced gap equal to approximately one-half the width of the eye between the anterior margin of the premaxilla and the posterior margin of the upper lip; and (4) ventral surface of the upper lip porous. In E. besouro the orbit is covered by skin and the anterobasal margins of the teeth of the first row are immobile and firmly attached on the ventral surface of the premaxilla, thus distinct from the state described for species of Archolaemus. However, the latter two characters are observed in E. besouro and may represent homoplasies, as discussed by these authors when considering the same condition present in some species of the E. trilineata species-group. Recently, Dutra et al. (2014) diagnosed Distocyclus by four autapomorphies: (1) a conical snout; (2) a small nasal capsule, with the internarial distance equal to the diameter of the posterior nostril; (3) the absence of endopterygoid teeth; and (4) a single tooth row limited to the anterior portion of dentary. Eigenmannia besouro shows a rounded snout in profile, the nasal capsule is moderate in size, with the internarial distance equal to two and a half times the diameter of the posterior nostril, the endopterygoid has ten or 11 teeth distributed in two rows, and the dentary has 19���30 teeth distributed in two or three complete rows. Therefore, E. besouro does not fit into the definition of Distocyclus provided by Dutra et al. (2014). Finally, Correa et al. (2006) defined Rhabdolichops by: (1) absence of scales above the lateral line on the anterior portion of the body; (2) premaxilla trapeizodal and elongate; (3) presence of two prootic foramina; (4) extrascapular fused with the neurocranium; (5) gill rakers long and bony; and (6) gill rakers ossified. In E. besouro, the region above the lateral line on the anterior portion of the body is covered by scales and the premaxilla is approximately rectangular. Additionally, the new species shows only one prootic foramen, the extrascapular is independent from the neurocranium, and the gill rakers are short and not ossified. It is, therefore, distinct from species of Rhabdolichops. The E. trilineata species-group is defined by the presence of the superior midlateral stripe, which is an exclusive synapomorphy for this clade (Peixoto et al., 2015). In view of the presence of this character, E. besouro is hypothesized as a member of this clade. Within this group, E. besouro shares with E. viscentespelaea and E. waiwai the subterminal position of the mouth, so it is possible that these three species comprise a monophyletic group, since the remaining species present a terminal mouth. Moreover, E. besouro shares with E. waiwai the depth of the posterodorsal expansion on infraorbitals 1 + 2 less than 40 % of the length of infraorbitals 1 + 2, and this character may represent a synapomorphy for these two species., Published as part of Peixoto, Luiz Ant��nio W. & Wosiacki, Wolmar B., 2016, Eigenmannia besouro, a new species of the Eigenmannia trilineata species-group (Gymnotiformes: Sternopygidae) from the rio S��o Francisco basin, northeastern Brazil, pp. 262-270 in Zootaxa 4126 (2) on pages 263-269, DOI: 10.11646/zootaxa.4126.2.6, http://zenodo.org/record/264520, {"references":["Peixoto, L. A. W, Dutra, G. M. & Wosiacki, W. B. (2015) The Electric Glass Knifefishes from the Eigenmannia trilineata speciesgroup (Gymnotiformes: Sternopygidae): monophyly and description of seven new species. Zoological Journal of Linnean Society, 175, 384 - 414. http: // dx. doi. org / 10.1111 / zoj. 12274","Mago-Leccia, F. (1994) Electric Fishes of the Continental Waters of America. Classification and Catalogue of the Electric Fishes of the Order Gymnotiformes (Teleostei: Ostariophysi) with Descriptions of New Genera and Species. Biblioteca de la academia de ciencias fisicas, matematics y naturales, 29, 1 - 225.","Albert, J. S. & Campos-da-Paz, R. (1998) Phylogenetic systematics of American knifefishes: a review of the available data. In: Malabarba, L. R., Reis, R. E, Vari, R. P., Lucena, Z. M. & Lucena, C. A. S (Eds.), Phylogeny and Classification of Neotropical Fishes. Edipucrs, Porto Alegre, pp. 419 - 446.","Albert, J. S. (2001) Species diversity and phylogenetic systematics of American knifefishes (Gymnotiformes, Teleostei). Miscellaneous Publication, Museum of Zoology, University of Michigan, 190, 1 - 127.","Dutra, G. M, de Santana, C. D, Vari R. P. & Wosiacki, W. B. (2014) The South American Electric Glass Knifefish genus Distocyclus (Gymnotiformes: Sternopygidae): Redefinition and Revision. Copeia, 2014 (2), 345 - 354. http: // dx. doi. org / 10.1643 / CI- 13 - 066","Correa, S. B., Crampton, W. G. R. & Albert, J. S. (2006) Three new species of the neotropical electric fish Rhabdolichops (Gymnotiformes: Sternopygidae) from the Central Amazon, with a new diagnosis of the genus. Copeia, 2006 (1), 27 - 42. http: // dx. doi. org / 10.1643 / 0045 - 8511 (2006) 006 [0027: tnsotn] 2.0. co; 2"]}

Eigenmannia besouro, new species (Figure 1) Holotype. MZUSP 57890, 91.9 mm LEA, Brazil, Bahia, São Desidério, Sítio Grande, rio São Francisco basin, rio Grande, 12 ° 25 ' 40.09 "S 45 °05' 10 "W, O. Oyakawa, A. Akama & V. Garutti, 8 Jul 1998. Paratypes. All from rio São Francisco basin, Brazil. Bahia: MZUSP 57889, 3, 94.6–105.4 mm LEA, São Desidério, rio São Desidério, O. Oyakawa, A. Akama & V. Garutti, 7 Jul 1998; MZUSP 57895, 1, 117.93 mm LEA, Formosa do Rio Preto, rio Preto, 11 ° 3 ' 15 "S 45 ° 12 ' 6 "W, O. Oyakawa, A. Akama & V. Garutti, 3 Jul 1998. MZUSP 83792, 6+ 1 CS, 55.8–68.8 mm LEA, Formosa do Rio Preto, rio Preto, 11 ° 8 ' 28 "S 46 ° 4 ' 1 "W, C. Moreira & J. Nolasco, 15 Nov 2002; MZUSP 84036, 7, 44.3–61.3 mm LEA, Formosa do Rio Preto, rio Preto, 11 ° 8 ' 28 "S 46 ° 4 ' 1 "W, C. Moreira, J. Nolasco & M. Avila, 3 Aug 2002; MZUSP 84070, 6, 13.9–100.1 mm LEA, Formosa do Rio Preto, rio Sapão, tributary to rio Preto, 10 ° 55 ' 39 "S 45 ° 41 ' 54 "W, C. Moreira & J. Nolasco, 6 Aug 2002; MZUSP 84113, 1, 75.9 mm LEA, Formosa do Rio Preto, rio Preto, 11 ° 2 ' 59 "S 45 ° 11 ' 31 "W, C. Moreira & J. Nolasco, 20 Nov 2002; MZUSP 98748, 2, 65.6 –81.0 mm LEA, Barra, rio Grande, 11 ° 6 ' 8 "S 43 ° 9 ' 26 "W, O. Oyakawa, A. Akama, V. Garutti & J. Nolasco, 10 Apr 2001; MZUSP 114281, 1, 80.6 mm LEA, Luís Eduardo Magalhães, rio Veredinha, rio Grande, 11 ° 10 ' 1.5 "S 44 ° 17 ' 9.3 "W, J. Birindelli, F. Dagosta, M. Loeb & C. Santos, 4 Dez 2012; MZUSP 114520, 2, 10.9–26.8 mm LEA, São Desidério, rio Galheirão, rio Grande, 12 ° 29 ' 29.3 "S 45 ° 12 ' 7.2 "W, O. Oyakawa, A. Zanata, P. Camelier & M. Melo, 4 Dec 2012; MZUSP 115398, 1, 50.3 mm LEA, Barreiras, rio de Ondas, 12 ° 7 '37.00"S 45 ° 8 ' 18 "W, O. Oyakawa, A. Zanata, P. Camelier & M. Melo, 3 Dec 2012; MZUSP 119104, 5 + 1 CS, 69.6–106.1 mm LEA; MPEG 33920, 1, 87.9 mm LEA, same data as the holotype. MPEG 33919, 1 CS, 86.0 mm LEA, Formosa do Rio Preto, rio Sapão, tributary to rio Preto, 10 ° 55 ' 39 "S 45 ° 41 ' 54 "W, C. Moreira & J. Nolasco, 6 Aug 2002. MPEG 33921, 1, 93.2 mm LEA, São Desidério, rio São Desidério, O. Oyakawa, A. Akama & V. Garutti, 7 Jul 1998. Diagnosis. Eigenmannia besouro can be distinguished from its congeners, except species of the Eigenmannia trilineata species-group, by the presence of the superior midlateral stripe (vs. absence). Eigenmannia besouro differs from species of the Eigenmannia trilineata species-group, except E. vicentespelaea and E. waiwai, by the subterminal mouth (vs. terminal). Eigenmannia besouro can be further differentiated from the striped species of Eigenmannia, except E. vicentespelaea, by the more anterior origin of the superior midlateral stripe, at vertical between base of 5 th to 15 th anal-fin ray in specimens larger than 65 mm LEA (vs. origin at vertical between 18 th to 35 th anal-fin ray). Eigenmannia besouro can be differentiated from E. vicentespelaea by: the number of pectoral-fin rays, ii, 13–14 (vs. ii, 15–17); the dentition pattern of dentary, 19–30 teeth distributed in two or three rows [outermost row with 7–14 teeth; median row with nine; innermost row with 7–13 teeth] (vs. 38–45 distributed in three or four rows [outermost row with 12–21 teeth; the second row with 14–16 teeth; the third row with ten teeth; the innermost row with 2–10 teeth]); and the depth of posterodorsal expansion on infraorbitals 1 + 2 less than 40 % of the length of infraorbitals 1 + 2 (Fig. 2) (vs. corresponds approximately to total length of infraorbitals 1 + 2). Eigenmannia besouro is distinguished from E. waiwai by: the anterodorsal process of the maxilla equal to the width of the posterior nostril (Fig. 3 a) (vs. equal to 1.5 times of the width of the posterior nostril; Fig. 3 b); the anterodorsal process of the premaxilla abruptly directed anteroventrally (Fig. 3 a) (vs. by the anterodorsal process of the premaxilla gradually directed anteroventrally; Fig. 3 b); the dentition pattern of the premaxilla, 18–29 teeth distributed in three or four rows [outermost row with 4–10 teeth; second row with 5–11 teeth; third row with 6–8 row; innermost row with six teeth] (Fig. 4) (vs. 35–40 distributed in five rows [outermost row with 4–10 teeth; second row with seven or eight teeth; third row with eight or nine teeth; fourth row with 7–9 teeth; innermost row with six teeth]); and the dentition pattern of the dentary, 19–30 teeth distributed in two or three rows [outermost row with 7–14 teeth; median row with nine; innermost row with 7–13 teeth] (vs. 37–38 distributed in four rows [outermost row with seven teeth; second row with 11–15 teeth; third row with 8–15; innermost row with 4–8 teeth]). Description. Species of medium size for Eigenmannia, maximum length 147.6 mm TL. Morphometric data in Table 1. Body elongate and laterally compressed. Dorsal profile of body nearly straight from rear of head to vertical through middle of anal fin, and then posteroventrally aligned to distal portion of caudal filament. Ventral profile of body slightly concave along anterior half of abdominal cavity; then posterodorsally aligned to last analfin ray. Ventral profile of caudal filament straight. Greatest body depth at vertical through pectoral-fin distal margin. Head laterally compressed, greatest width at opercular region and greatest depth at posteior margin of supraoccipital. Dorsal profile of head convex from upper lip to vertical through branchial opening. Ventral profile of head slightly concave from anterior margin of lower lip to branchial opening. Snout rounded in lateral profile. Mouth subterminal. Upper lip slightly overlapping lower lip. Premaxilla teeth, 18 (1) 21 (1) or 29 (1) in three or four rows [outermost row with 4 (1), 6 (1) or 10 (1) teeth; second row with 5 (2) or 11 (1); third row with 6 (1), 7 (1) or 8 (1) teeth; innermost row with 6 (1) teeth]. Maxilla with sickle-shaped anterodorsal process equal to width of posterior nostril. Dentary teeth, 19 (1), 23 (1) or 30 (1) in two or three rows [outermost row with 7 (1), 10 (1) or 14 (1) teeth; median row teeth, 9 (1); innermost row teeth, 7 (1), 12 (1) or 13 (1)]. Dentary teeth similar in size. Coronomeckelian bone equal to 30 % of Meckel’s cartilage length. Endopterygoid teeth, 10 (1) or 11 (2) in two rows. Mouth rictus at vertical through anterior nostril or in region between nares. Anterior naris tube-like, posterior margin at vertical through posterior margin or in median portion of rictus. Posterior nares elliptical, without tube, closer to anterior margin of eye than snout tip. Eye approximately circular, covered by skin, positioned laterally on anterior half of head. Antorbital and infraorbitals 1–4 as enlarged, partial cylinders with slender bony arches. Fifth and sixth infraorbitals slender and tubular. Depth of posterodorsal expansion on infraorbitals 1 + 2 equals 40 % of length of infraorbitals 1 + 2. Branchial opening moderately elongate. Branchial membrane joined to isthmus. Anus and urogenital papilla shifting anteriorly ontogenetically. Anus and urogenital papilla at vertical through posterior margin of orbit in mature specimens. Holotype Min Max Mean SD N Total length (mm) 127.0 70.5 147.6 – – 20 Length to end of anal fin (mm) 91.9 49.4 106.1 – – 20 Head length (mm) 12.9 7.7 13.7 – – 20 Percentage of LEA Head length 14.0 12.5 15.6 14.0 0.8 20 Preanal distance 18.8 16.3 19.4 18.0 0.8 20 Prepectoral distance 14.7 14.1 16.4 15.1 0.6 20 Snout to anus 8.6 6.1 13.1 9.2 2.1 20 Body depth at pectoral fin 17.9 13.6 17.9 15.1 0.9 20 Body depth at anal fin 15.8 13.0 16.1 14.4 0.8 20 Body width 6.2 5.2 7.5 6.2 0.6 20 Anal-fin length 82.1 79.3 87.0 83.6 2.1 20 Pectoral-fin length 10.3 8.1 11.0 10.0 0.7 20 Caudal filament length 36.3 26.7 53.8 41.9 6.7 20 Caudal filament depth 1.6 0.6 2.1 1.3 0.4 20 Caudal filament width 0.8 0.4 1.0 0.6 0.1 20 Pecentage of HL Snout length 26.7 23.7 31.9 28.0 2.2 20 Internasal distance 8.2 6.0 10.5 8.4 1.0 20 Snout to posterior naris distance 16.9 16.9 23.4 20.3 1.7 20 Posterior naris to orbit distance 7.4 4.4 9.2 6.6 1.1 20 Internarial width 15.5 10.7 22.6 14.6 2.3 20 Orbital diameter 24.6 16.9 25.1 20.5 2.3 20 Postorbital distance 54.5 46.9 55.9 50.8 2.5 20 Opercular opening 28.8 20.1 29.1 25.2 2.6 20 Suborbital depth 23.2 18.3 24.8 22.3 1.7 20 Interorbital distance 29.8 25.6 38.6 31.5 3.6 20 Head width at opercle 53.4 50.3 67.0 56.3 3.9 20 Head width at orbits 45.1 30.6 50.1 40.6 4.9 20 Head depth at supraoccipital 74.7 67.0 80.9 74.2 3.4 20 Head depth at orbits 56.6 49.8 59.5 55.0 3.1 20 Maxilla length 18.4 14.3 23.8 19.0 2.8 20 Oral width 16.1 9.5 19.1 13.4 2.6 20 Cycloid scales from immediately posterior to head to distal portion of caudal filament. Lateral line complete, 96 (1), 98 (3), 99 (1), 100 (1), 101 (1), 102 *(2), 104 (1), 105 (1), 107 (1), 110 (1), 111 (1), 113 (2), 114 (1), 116 (2), 118 (1) or 120 (1) perforated scales to vertical through end of anal fin. Longitudinal series of scales above lateral line at midbody, 7 (4), 8 *(12), 9 (3) or 10 (1). Scales over anal-fin pterygiophores approximately half size of others. Pectoral-fin rays, ii, 13 (6) or ii, 14 *(15); distal margin slightly rounded; tip reaching vertical through 20 th to 25 th anal-fin rays. Anal-fin origin posterior to vertical through pectoral-fin base; total anal-fin rays, 1 50–181 [168 *] (N= 21); distal margin of anal fin slightly convex. Caudal filament cylindrical, tapering gradually distally, moderate size, approximately 45 % of LEA in mature specimens. Precaudal vertebrae, 14 (3). Anterior vertebrae, 11 (2) or 12 (1), transitional vertebrae, 2 (1) or 3 (2). Displaced hemal spines, 3 (3). Coloration in alcohol. Background color dark brown. Dorsal region of head dark brown; gradually becoming lighter ventrally. Lips and suborbital region light brown. Dorsal region of body dark brown, gradually lighter in region overlying anal-fin pterygiophores. Four longitudinal dark stripes along body. Lateral-line stripe thin, one or two scales deep, extending from first perforated lateral-line scale to distal portion of caudal filament. Superior midlateral stripe thick, two or three scales deep, tapering from vertical between base of 5 th to 15 th anal-fin ray to posterior two-thirds of body in specimens over 65 mm LEA; or tapering from vertical between base of 25 th to 36 th anal-fin ray to posterior two-thirds of body in specimens up to 60 mm LEA. Inferior midlateral stripe moderately thick, two or three scales deep, extending from vertical between base of 15 th to 28 th anal-fin ray to posterior onethird of body. Anal-fin base stripe thick, two scales deep, extending from vertical between base of first and 26 th anal-fin ray to last anal-fin ray. Pectoral and anal fins hyaline, with scattered tiny chromatophores on interradial membranes. Remarks. Recently, Peixoto et al. (2015) redescribed E. microstoma and recorded the rio São Francisco basin as its range, the same hydrographic basin of E. besouro. Aiming to clarify the differences between the two species, some diagnostic characters are presented. Eigenmannia besouro differs from E. miscrostoma by: mouth subterminal (vs. terminal); suborbital depth, 18.3–24.8 % HL (vs. 29.9–40.8 %); number of scale series above lateral line, 7–10 (vs. 11-15); depth of the posterodorsal expansion on infraorbitals 1 + 2 less than 40 % of the length of infraorbitals 1 + 2 (vs. approximately equal to the total length of infraorbitals 1 + 2); and length of the coronomeckelian bone equivalent to 30 % of the length of Meckel’s cartilage (vs. equals 45 % of the length of Meckel’s cartilage). Distribution. Eigenmannia besouro is known from tributaries of the left margin of rio São Francisco, Bahia, northeastern Brazil (Fig. 5). Etymology. The species name, besouro (‘beetle’ in Portuguese) is in honor of Manoel Henrique Pereira, known as Besouro Mangangá (‘The Mangangá Beetle’), a native of the Recôncavo region of Bahia, and a legendary figure in the Afro-Brazilian martial art capoeira; a noun in opposition. Discussion. Given the absence of proposed synapomorphies for Eigenmannia (Mago-Leccia, 1994; Albert & Campos-da-Paz, 1998; Albert, 2001), we consider it more appropriate to assign E. besouro provisionally as a member of this genus because it does not have most of the synapomorphies present in the remaining genera of Eigenmaniinae. Vari et al. (2012) proposed six synapomorphies for Japigny: (1) color pattern composed by alternating dark bands; (2) presence of single row teeth at the base of the upper oral valve; (3) lateral process of the parapophysis of the second vertebrae ventrally curved; (4) distinct separation of the lateral process of the second vertebrae from the parapophysis of the fourth vertebrae; (5) lateral process of the parapophysis of the fourth vertebrae ventrally curved; and (6) retroarticular not included in the socket of the lower jaw with the quadrate. In Eigenmannia besouro, the color pattern is composed of four longitudinal dark stripes without alternating dark bands on flanks. Additionally, the single row of teeth at the base of the upper oral valve is absent, the contact of the lateral process of the second vertebrae with the parapophysis of the fourth vertebrae is present, and the retroarticular is included in the socket of the lower jaw with the quadrate, distinct from the states described by Vari et al. (2012) for Japigny. These features argue against the inclusion of the new species in Japigny. However, the ventral curvature of the lateral process of the parapophysis of the second and fourth vertebrae is present in E. besouro, as well as in most genera of the Eigenmanniinae, and may represent a plesimorphic condition in the subfamily. In the same study, Vari et al. (2012) proposed four synapomorphies for Archolaemus: (1) a free orbital rim; (2) anterobasal margins of the teeth of the first tooth row attached to the dentigerous surface of the premaxilla; (3) pronounced gap equal to approximately one-half the width of the eye between the anterior margin of the premaxilla and the posterior margin of the upper lip; and (4) ventral surface of the upper lip porous. In E. besouro the orbit is covered by skin and the anterobasal margins of the teeth of the first row are immobile and firmly attached on the ventral surface of the premaxilla, thus distinct from the state described for species of Archolaemus. However, the latter two characters are observed in E. besouro and may represent homoplasies, as discussed by these authors when considering the same condition present in some species of the E. trilineata species-group. Recently, Dutra et al. (2014) diagnosed Distocyclus by four autapomorphies: (1) a conical snout; (2) a small nasal capsule, with the internarial distance equal to the diameter of the posterior nostril; (3) the absence of endopterygoid teeth; and (4) a single tooth row limited to the anterior portion of dentary. Eigenmannia besouro shows a rounded snout in profile, the nasal capsule is moderate in size, with the internarial distance equal to two and a half times the diameter of the posterior nostril, the endopterygoid has ten or 11 teeth distributed in two rows, and the dentary has 19–30 teeth distributed in two or three complete rows. Therefore, E. besouro does not fit into the definition of Distocyclus provided by Dutra et al. (2014). Finally, Correa et al. (2006) defined Rhabdolichops by: (1) absence of scales above the lateral line on the anterior portion of the body; (2) premaxilla trapeizodal and elongate; (3) presence of two prootic foramina; (4) extrascapular fused with the neurocranium; (5) gill rakers long and bony; and (6) gill rakers ossified. In E. besouro, the region above the lateral line on the anterior portion of the body is covered by scales and the premaxilla is approximately rectangular. Additionally, the new species shows only one prootic foramen, the extrascapular is independent from the neurocranium, and the gill rakers are short and not ossified. It is, therefore, distinct from species of Rhabdolichops. The E. trilineata species-group is defined by the presence of the superior midlateral stripe, which is an exclusive synapomorphy for this clade (Peixoto et al., 2015). In view of the presence of this character, E. besouro is hypothesized as a member of this clade. Within this group, E. besouro shares with E. viscentespelaea and E. waiwai the subterminal position of the mouth, so it is possible that these three species comprise a monophyletic group, since the remaining species present a terminal mouth. Moreover, E. besouro shares with E. waiwai the depth of the posterodorsal expansion on infraorbitals 1 + 2 less than 40 % of the length of infraorbitals 1 + 2, and this character may represent a synapomorphy for these two species.

One of the most studied weakly electric fish, Eigenmannia produces a continuous high frequency electric organ discharge (EOD) used to sense nearby objects and communicate with conspecifics. The EOD of an individual fish has a characteristic frequency (within the species range, 250-600 Hz) which it shifts when necessary to avoid jamming. The nearly dipolar oscillating electric field yields zero net current and is generated by parallel columns of identical, synchronously discharging electrocyte cells. Recent findings from whole fish respirometry (during high-frequency signaling over a range of frequencies) have renewed interest in the frequency-dependent energetics of the EODs (Lewis et al 2014 J Neurosci 34:197) but the modeling based on past analyses is missing some key features of the in-vivo electrolyte operation. We have constructed a model for the neurally-driven electrocyte action potentials (APs) that underlie the EOD. APs are initiated by brief post-synaptic cation influxes through AChR channels at each electrocyte's innervated posterior end. This yields a head positive current while the anterior end serves mainly as a capacitor whose discharge yields the head negative current of the oscillating dipole cycle. To maintain the appropriate [Na]in and [K]out levels, Na/K-ATPase pumps run continuously. Modeling the activity of this ATP consuming protein gives us access to electrocyte energetics and frequency-dependent EOD efficiency. Modeling the posterior-anterior current flows gives us access to the electric field patterns produced by the electrocytes.

The genus Myxobolus, parasites that infect fishes, which cause myxobolosis, includes spore organisms belonging to the phylum Myxozoa and represents approximately 36% of all species described for the entire phylum. This study describes lymphocytic meningoencephalomyelitis associated with Myxobolus sp. infection in the brain and spinal cord (the central nervous system, CNS) of Eigenmannia sp., from the Amazon estuary region, in the Administrative District of Outeiro (DAOUT), Belém, Pará, Brazil. In May and June 2015, 40 Eigenmannia sp. specimens were captured from this region and examined. The fish were anesthetized, slaughtered and dissected for sexing (gonad evaluation) and studying parasites and cysts; after diagnosing the presence of the myxozoans using a light microscope, small fragments of the brain and spinal cord were removed for histological processing and Hematoxylin-Eosin and Ziehl-Neelsen staining. Histopathological analysis of the brain and spinal cord, based on histological sections stained with Hematoxylin-Eosin, pronounced and diffuse edema in these tissues, and congestion, degeneration, and focal necrosis of the cerebral cortex. The present study describes lymphocytic meningoencephalomyelitis associated with infection by Myxobolus sp. in the central nervous system of Eigenmannia sp. Resumo O gênero Myxobolus é composto por parasitas esporais que podem infectar peixes e causar a “myxobolose”. São organismos pertencentes ao filo Myxozoa e representam cerca de 36% do total de espécies descritas para todo o Filo. Este estudo descreve meningoencefalomielite linfocitária, associada à infecção por Myxobolus sp. no cérebro e medula espinhal (SNC) de Eigenmannia sp, oriundo de região estuarina amazônica, no Distrito Administrativo de Outeiro (DAOUT), município de Belém, Pará, Brasil. Foram capturados e examinados 40 espécimes de Eigenmannia sp. entre os meses de maio e junho de 2015. Os peixes foram anestesiados, abatidos e dissecados para sexagem (avaliação das gônadas) e pesquisa de parasitos e cistos. Após o diagnóstico da presença dos mixosporidios, utilizando-se microscópio de luz, pequenos fragmentos do cérebro e da medula espinal foram removidos para processamento histológico e coloração por Hematoxilina-Eosina e coloração especial em Ziehl-Neelsen. A análise histopatológica do cérebro e da medula espinhal, com base em cortes histológicos corados com Hematoxilina-Eosina, mostrou edema difuso nesses tecidos, e congestão, degeneração e necrose focal do córtex cerebral. O presente estudo descreve meningoencefalomielite linfocítica, associada à infecção por Myxobolus sp., no sistema nervoso central de Eigenmannia sp.

In this paper, we implement a model of an electric fish, Eigenmannia, that detects frequency differences between the individuals, on analog CMOS circuits. The circuit's fundamental function is equivalent to a conventional “phase frequency comparator”. The circuit consists of five elemental cell units that implement neural networks of the electric fish. Using a simulation program of integrated circuit emphasis (SPICE), we demonstrate that the proposed circuit can detect the frequency difference.

Biomimetic photonics extract the good design of nature and mimic it with photonics. The weakly electric fish genus, Eigenmannia, has a unique neural algorithm - jamming avoidance response, to facilitate their survival in the deep dark ocean, by automatically adjusts the local transmitter carrier frequency to move away from the jamming frequency when it is within the jamming spectral range. Examining our own wireless microwave systems, the situation of inadvertent jamming is very similar as that in Eigenmannia. In this article, a biomimetic photonic approach inspired by the jamming avoidance response in a weakly electric fish genus, Eigenmannia, is naturally adopted to experimentally tackle signal jamming in wireless systems. Mimicking the system with photonics enables the proposed scheme to work for frequencies from hundreds of MHz to tens of GHz.

The genus Eigenmannia belongs to the family Sternopygidae, a monophyletic group of Neotropical electrogenic fish. Eigenmannia trilineata from Iguatemi River basin were analyzed using classical cytogenetic techniques. Chromosomes of this species of Eigenmannia presented a X1X1X2X2 : X1X2Y sex chromosome system, with 2n=31chromosomes for the males and 2n=32 for the females, where the Y is metacentric chromosome originated from Robertsonian translocation. The NORs are located interstitially on the long arm of chromosome pair 10. Constitutive heterochromatin is distributed in very conspicuous blocks at the juxtacentromeric regions acrocentrics chromosomes in the males and females, including the unique large metacentric neo-Y in the males also presented a juxtacentromeric block. The chromosomal data obtained may be useful for the taxonomy and phylogenetic studies in this fish group.

The genus Eigenmannia (Teleostei: Gymnotiformes), a widely distributed fish genus from the Neotropical region, presents very complex morphological patterns and many taxonomic problems. It is suggested that this genus harbors a species complex that is hard to differentiate using only morphological characteristics. As a result, many species of Eigenmannia may be currently gathered under a common name. With the objective of providing new tools for species characterization in this group, an analysis of the polymorphism of DNA inter-simple sequence repeats (ISSR), obtained by single primer amplification reaction (SPAR), combined with karyotype identification, was carried out in specimens sampled from populations of the Upper Paraná, São Francisco and Amazon river basins (Brazil). Specific ISSR patterns generated by primers (AAGC)(4) and (GGAC)(4) were found to characterize the ten cytotypes analyzed, even though the cytotypes 2n = 38 and 2n = 38 XX:XY, from the Upper Paraná basin, share some ISSR amplification patterns. The geographical distribution of all Eigenmannia specimens sampled was inferred, showing the cytotype 2n = 31/2n = 32 as the most frequent and largely distributed in the Upper Paraná basin. The cytotype 2n = 34 was reported for the first time in the genus Eigenmania, restricted to the São Francisco basin. Polymorphic ISSR patterns were also detected for each cytotype. Considering our results and the data reported previously in the literature, it is suggested that many of the forms of Eigenmannia herein analyzed might be regarded as different species. This work reinforces the importance of employing diverse approaches, such as molecular and cytogenetic characterization, to address taxonomic and evolutionary issues.

The Neotropical genus Eigenmannia is a fish group with unknown species diversity where representatives possess a broad range of chromosomal sex determining systems namely XY/XX, X1X2Y/X1X1X2X2, ZZ/ZW as well as homomorphic sex chromosomes. To test the homology of two heteromorphic XY sex chromosome systems present in two sympatric populations, reciprocal cross-species FISH experiments were performed using probes derived by microdissection of X and Y chromosomes present in analyzed specimens of Eigenmannia virescens and Eigenmannia sp.2, respectively. While X and Y paint probes hybridized to species-specific sex chromosomes, in reciprocal cross-FISH both probes hybridized exclusively to autosomes. The result suggests multiple independent origins of the XY systems in the analyzed populations.

How do neural systems process sensory information to control locomotion? The weakly electric knifefishEigenmannia, an ideal model for studying sensorimotor control, swims to stabilize the sensory image of a sinusoidally moving refuge. Tracking performance is best at stimulus frequencies less than ∼1 Hz. Kinematic analysis, which is widely used in the study of neural control of movement, predicts commensurately low-pass sensory processing for control. The inclusion of Newtonian mechanics in the analysis of the behavior, however, categorically shifts the prediction: this analysis predicts that sensory processing is high pass. The counterintuitive prediction that a low-pass behavior is controlled by a high-pass neural filter nevertheless matches previously reported but poorly understood high-pass filtering seen in electrosensory afferents and downstream neurons. Furthermore, a model incorporating the high-pass controller matches animal behavior, whereas the model with the low-pass controller does not and is unstable. Because locomotor mechanics are similar in a wide array of animals, these data suggest that such high-pass sensory filters may be a general mechanism used for task-level locomotion control. Furthermore, these data highlight the critical role of mechanical analyses in addition to widely used kinematic analyses in the study of neural control systems.