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In a recent expedition to the rio Grande basin, a tributary of the rio Parana in southern Brazil, individuals of the armoured catfish genus Hypostomus with a peculiar and beautiful colour pattern composed of pale vermiculations on the head and four to five horizontal stripes on the flanks were collected. Initially, the specimens were identified as a colour morph of the pale-spotted H. margaritifer. However, when we compared their partial cytochrome C oxidase subunit I (COI) mitochondrial gene to sequences of some typically pale-spotted H. margaritifer, the striped specimens were genetically distinct. Further analysis of the striped individuals revealed that they are the poorly known but valid species Hypostomus variipictus, which was described by Ihering in 1911 from the rio Pardo, a tributary of the rio Grande, upper rio Parana basin, in Sao Paulo State, Brazil. Since its descriptions, no robust taxonomic work has been published concerning this species. In this study, the newly sampled population was compared to the original description and to the holotype of H. variipictus, providing the foundation for a complete redescription, proper diagnosis, and first live colour illustration and description of the previously hidden H. variipictus.

Environmental disasters affecting Brazilian rivers have been frequent recently, especially involving mining activities. Two recent dam-rupture events suddenly released millions of cubic meters of iron tailings downstream into two major Brazilian watersheds. These events generated major losses to the environment and human life. Additionally, the biodiversity in both watersheds was still incompletely known. Two new species of the armoured catfish genus Hypostomus were discovered in the Rio Paraopeba and surrounding rivers of the Rio São Francisco Basin. The species share some main characteristics including a depressed body, large dark spots on a clearer background and the absence of keels on flanks. However, while one species (Hypostomus freirei sp. n.) has a large mandibular ramus and numerous slender teeth, the other (Hypostomus guajupia sp. n.) has a shorter mandibular ramus and few robust teeth. The discovery of these two new mid-sized fish species emphasizes the presumption that the effects of major environmental disasters cannot be fully estimated as local biodiversity is not completely known. This discovery in a recently devastated area also shows that tough environmental laws for the protection, supervision and mitigation of major impacts are urgently needed in developing countries.

Chaetostoma chimu sp. nov. is described from 119 specimens collected in the Andean foothills of the Orinoco River in Colombia. The new species can be distinguished from congeners by a combination of characters, including shape of cheek odontodes, presence of a supraoccipital excrescence, sexual dimorphism characters and colour pattern. In addition, this species can be distinguished from the sympatric and geographically close congeners of the Orinoco that have curved cheek odontodes (i.e., Chaetostoma anale, Chaetostoma formosae and Chaetostoma joropo), by presenting a generally larger orbital diameter and interorbital distance, details of sexual dimorphism and colour pattern. The type locality of specimens collected by Kjell von Sneidern in the mid-twentieth century in the Colombian Amazon is also clarified. Chaetostoma alternifasciatum and Chaetostoma vagum are proposed as junior synonyms of C. anale. An identification key for the species of Chaetostoma from cis-Andean drainages in Colombia is provided. The new species is herein categorized as Vulnerable (Vu) B1a (i, iii), following the IUCN criteria.

This study presents the first information on the reproduction of the recently described tiger pleco Panaqolus tankei, from Lake Bolonha in the north-eastern Amazon Basin. This loricariid has a long reproductive period, fractionated spawning and low fecundity (on average, female gonads contained 37 oocytes), a total length (LT ) at first maturity of 47.4 mm for females and 54.1 mm LT for males. Correlation of the condition factor and gonado-somatic index with environmental variables suggests that turbidity favours P. tankei reproduction in this environment.

A recent expedition to headwaters of the Rio Pandeiros, a left-bank tributary of the Rio São Francisco revealed the presence of a fourth species of Hisonotus from that basin. Hisonotus devidei sp. nov. differs from congeners by the presence of conspicuous dark blotches of distinct shapes irregularly arranged along lateral and dorsal surfaces of the body and scattered throughout all fins, by possessing small plates in lateral portions of the abdomen and adjacent areas between pelvic fins without development of dermal plates and by morphometric ratios. The putative phylogenetic placement of the new species is discussed based on morphological comparisons with species of related Hypoptopomatinae genera and the Hisonotus species diversity within the Rio São Francisco Basin is compared with that of adjacent basins.

A re-evaluation of Dekeyseria brachyura and D. pulchra found them to be junior synonyms of D. picta, the oldest species among these congeners, based on continuous intraspecific variation in morphometrics and colour pattern. Examination of material deposited at Brazilian and Venezuelan collections, including the original type specimens of Ancistrus brachyurus and A. pictus, plus samples recently collected in the Rio Negro, Amazonas, Brazil, allowed re-evaluation of the taxonomic status of D. picta and provides additional information on its distribution, habitats and reproductive strategies.

A new species of the genus Sturisoma from the Madre de Dios River, upper Madeira, Peru, is described. The new species can be differentiated from its congeners by the following characteristics: dorsolateral stripe reaching to less than half, or only half length of caudal peduncle (v. absence of dorsolateral stripe or, if present, spanning more than half caudal-peduncle length); premaxillary teeth longer than dentary teeth (v. dentary teeth longer); sexually mature adult males having well-developed odontodes on the sides of the head and a broader snout (v. adult males lacking well-developed hypertrophied odontodes or, if present, rostrum is same width as females' or immature males'); by having the ventral portion of the rostrum conspicuously darker than ventral surface of the body (v. rostrum light, with same colour as ventral portion of body, except in Sturisoma barbatum); by lacking the lateral process of the sphenotic (v. lateral process of sphenotic well-developed, except in Sturisoma tenuirostre); a dark spot on the first three branched pectoral-fin rays (v. brown spot absent, except in S. barbatum); and the frontal bone contributing less than half of dorsal border of the orbital ridge (v. extensive participation of the frontal, except in Sturisoma guentheri). Furthermore, the new species has 18-20 plates in the median series, which differentiates it from Sturisoma rostratum (21-22), and Sturisoma monopelte (21); and 14-15 coalescent plates, which differentiates it from S. tenuirostre (16-17). It is further differentiated from Sturisoma brevirostre by presence of an enlarged rostrum (v. rostrum not enlarged). A discussion regarding status of the type series and geographic distribution of Sturisoma rostratum is offered, and an identification key for all Sturisoma species is presented.

A new species of Spectracanthicus is described from the Rio Javaes, Rio Araguaia basin. The new species is distinguished from its congeners (except Spectracanthicus immaculatus) by colour pattern: body dark grey to dark brown without dots or blotches (v. body colour with yellowish small dots in Spectracanthicus murinus, Spectracanthicus punctatissimus and Spectracanthicus tocantinensis and large white dots in Spectracanthicus zuanoni). It can be further distinguished from S. immaculatus by having thicker and less numerous teeth, with up to eight premaxillary and 20 dentary teeth (v. teeth thinner and more numerous with up to 22 premaxillary and 30 dentary teeth); dorsal and caudal fins without curved spines (v. dorsal and caudal fins with curved spines). Other osteological characters can also diagnose the new species from its congeners. In addition, a gross brain description and brief comments on the new species' ecological habitat are given.

A re-evaluation of the armoured catfish species of Hypostomus in the Rio Jaguaribe, north-eastern Brazil, was prompted by the discovery of specimens with pale spots on a dark background collected from that basin c. 1936 and deposited at the Academy of Natural Sciences of Philadelphia. Recent field collections in the Rio Jarguaribe basin confirmed the presence of the pale-spotted specimens and its distinctiveness as a new species. Hypostomus sertanejo n. sp. is diagnosed from other species of Hypostomus by having fins and dermal-plated regions of head and body with pale spots or vermiculations on darker background, teeth slender, asymmetrically bicuspid and numerous (34-75) on dentary and premaxilla, depressed dorsal-fin spine not reaching adipose spine, unbranched pectoral-fin spine longer than unbranched pelvic-fin ray, seven branched dorsal-fin rays and one (rarely two) predorsal plate(s) bordering supraoccipital. Ancistrus salgadae Fowler 1941 is hypothesized to be a junior synonym of Hypostomus carvalhoi (Miranda-Ribeiro, 1937), a dark-spotted Hypostomus described from the Rio Granjeiro, a tributary to the upper Rio Salgado.

The genus Pseudacanthicus comprises six valid species distributed in the Amazon basin and Caribbean coastal drainages from Guyana to French Guiana: P. serratus, P. fordii, P. histrix, P. spinosus, P. leopardus and P. pitanga. A new species of Pseudacanthicus is described from the Rio Xingu Basin, distinguished from its congeners by the following combination of characters: presence of anastomose dark blotches forming continuous zigzag bands alongside longitudinal keels; presence of dark blotches on ventral surface of body and head; all fins with orange to red colour on unbranched rays and sometimes subsequent branched rays. Brief comments on ornamental fisheries and conservation of the new species are also provided.

Ecological opportunity is often proposed as a driver of accelerated diversification, but evidence has been largely derived from either contemporary island radiations or the fossil record. Here, we investigate the potential influence of ecological opportunity on a transcontinental radiation of South American freshwater fishes. We generate a species-dense, time-calibrated molecular phylogeny for the suckermouth armored catfish subfamily Hypostominae, with a focus on the species-rich and geographically widespread genus Hypostomus. We use the resulting chronogram to estimate ancestral geographical ranges, infer historical rates of cladogenesis and diversification in habitat and body size and shape, and test the hypothesis that invasions of previously unoccupied river drainages accelerated evolution and contributed to adaptive radiation. Both the subfamily Hypostominae and the included genus Hypostomus originated in the Amazon/Orinoco ecoregion. Hypostomus subsequently dispersed throughout tropical South America east of the Andes Mountains. Consequent to invasion of the peripheral, low-diversity Paraná River basin in southeastern Brazil approximately 12.5 Mya, Paraná lineages of Hypostomus, experienced increased rates of cladogenesis and ecological and morphological diversification. Contemporary lineages of Paraná Hypostomus are less species rich but more phenotypically diverse than their congeners elsewhere. Accelerated speciation and morphological diversification rates within Paraná basin Hypostomus are consistent with adaptive radiation. The geographical remoteness of the Paraná River basin, its recent history of marine incursion, and its continuing exclusion of many species that are widespread in other tropical South American rivers suggest that ecological opportunity played an important role in facilitating the observed accelerations in diversification.

This study taxonomically reviewed the specimens studied by Artoni & Bertollo (1996) and assimilated species of Hypostomus into three groups according to their cytogenetic characteristics, vagility and occurrence environments.

This study details 13 novel polymorphic microsatellite loci in the armoured catfish Hypostomus ancistroides, and assesses their utility for population genetic studies. The analysis of 30 individuals revealed a total of 99 different alleles (ranging from two to 15 alleles per locus), with an average of 7·62 alleles per locus, with observed and expected heterozygosities ranging from 0·103 to 0·931 and from 0·102 to 0·906, respectively. One of the 13 loci showed significant deviations from Hardy-Weinberg equilibrium, probably due to the presence of null alleles, inferred from the excess of homozygotes.

Of those fishes scraping food off substrates and using head parts in substrate attachment for station-holding, the catfish families Loricariidae, Astroblepidae and Mochokidae display the most dramatically adapted morphologies. Loricariidae and Astroblepidae, living in the Neotropical freshwaters, exclusively contain suckermouth catfish species, and their anatomy and head kinematics have already been studied into detail. Among Mochokidae, living in the tropical freshwaters of Africa, only the chiloglanidine subfamily has a sucker mouth, and occupies similar niches in Africa as both Neotropical families do in South America. Having derived from relatively unrelated catfish ancestors, their anatomy is poorly known, and the nature of their scraping and station-holding capabilities is not known at all. This paper provides details on the chiloglanidine head anatomy and function (relating their anatomy to that of the non-suckermouth Mochokidae), and compares this Afrotropical suckermouth taxon with both Neotropical suckermouth families. It identifies both convergences and differing anatomical and kinematic solutions to the same key needs of food-scraping and station-holding suckermouth fishes. Chiloglanidine mochokids differ from both Neotropical families in having less mobile jaws, with an upper jaw assisting more in station-holding than in feeding. They share the highly mobile lower lip with both Neotropical taxa, although the configuration of the intermandibular/protractor hyoidei muscle system, changing the volume of the sucker-disc cavity, differs in all three taxa. Chiloglanidines have a single, posterior inflow opening into this cavity, whereas Loricariidae have two lateral openings, and Astroblepidae have none, using an opercular incurrent opening instead. The chiloglanidine buccal valve system consists of two passive valves, as in Astroblepidae. Although less diverse in number of genera and species, this Afrotropical suckermouth taxon possesses the anatomical and kinematic key elements allowing a successful occupation of a niche similar to the one found in the Loricariidae + Astroblepidae clade.

Astroblepidae or “climbing catfishes” encompass a single genus of species living in high altitude rivers in the Andes of South America. They are characterized by a specialized head morphology closely resembling their better known, widely radiated sister family Loricariidae, or armored suckermouth catfishes. Existent data show that even though both families share important traits, there are some striking differences as well. Albeit poorly known, Astroblepus species possess a duplicated gill opening, and have the ability to climb vertical rocks or waterfalls. In this study, morphological and kinematic data are combined to yield insights into the functions of the mobile elements of the astroblepid head, and to compare head morphology and biomechanics with those of Loricariidae. We found that, even though there is substantial similarity in head structure of both families, there are major differences in functionally important structures. These include a different lower lip muscle configuration, an alternative oral valve system, and an incurrent gill opening only found in astroblepids. Kinematic analyses confirm that the astroblepid suckermouth, freed from its inhalatory function, offers advantages for climbing in the high-altitude environment, and is used alternately with the extremely mobile pelvic girdle, in a crawling, nonundulatory motion. J. Morphol. 274:1164–1179, 2013. © 2013 Wiley Periodicals, Inc.

Made available in DSpace on 2013-09-27T14:54:34Z (GMT). No. of bitstreams: 1 WOS000312451300007.pdf: 2789005 bytes, checksum: 1528f15168beefd419f1d17b01774e6e (MD5) Previous issue date: 2012-10-01 Made available in DSpace on 2013-09-30T18:45:42Z (GMT). No. of bitstreams: 1 WOS000312451300007.pdf: 2789005 bytes, checksum: 1528f15168beefd419f1d17b01774e6e (MD5) Previous issue date: 2012-10-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:51:46Z No. of bitstreams: 1 WOS000312451300007.pdf: 2789005 bytes, checksum: 1528f15168beefd419f1d17b01774e6e (MD5) Made available in DSpace on 2014-05-20T13:51:46Z (GMT). No. of bitstreams: 1 WOS000312451300007.pdf: 2789005 bytes, checksum: 1528f15168beefd419f1d17b01774e6e (MD5) Previous issue date: 2012-10-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Freshwater fish evolution has been shaped by changes in the earth's surface involving changes in the courses of rivers and fluctuations in sea level. The main objective of this study is to improve our knowledge of the evolution of loricariids, a numerous and adaptive group of freshwater catfish species, and the role of geological changes in their evolution. We use a number of different phylogenetic methods to test the relationships among 52 representative taxa within the Neoplecostominae using 4676 bps of mitochondrial and nuclear DNA. Our analysis revealed that the subfamily Neoplecostominae is monophyletic, including Pseudotocinclus, with three lineages recognized. The first lineage is composed of part of Pareiorhina rudolphi, P. cf. rudolphi, and Pseudotocinclus; the second is composed of Isbrueckerichthys, Pareiorhaphis, Kronichthys, and the species Neoplecostomus ribeirensis; and the third is composed of Pareiorhina carrancas, P. cf. carrancas, Pareiorhina sp. 1, a new genus, and all the species of the genus Neoplecostomus, except N. ribeirensis. The relaxed molecular clock calibration provides a temporal framework for the evolution of the group, which we use for a likelihood-based historical biogeographic analysis to test relevant hypotheses on the formation of southeast Brazil. We hypothesize that headwater capture events and marine regressions have shaped the patterns of distribution within the subfamily Neoplecostominae throughout the distinct basins of southeast Brazil. Univ Estadual Paulista, Dept Morfol, Inst Biociencias, Lab Biol & Genet Peixes,UNESP, BR-18618000 Botucatu, SP, Brazil Universidade Estadual de Maringá (UEM), Nupelia, UEM, Maringa, Parana, Brazil Univ Calif Santa Barbara, Dept Ecol Evolut & Marine Biol, Santa Barbara, CA 93106 USA Univ Estadual Paulista, UNESP, Dept Zool & Bot, Lab Ictiol, Sao Jose do Rio Preto, SP, Brazil Univ Estadual Paulista, Dept Morfol, Inst Biociencias, Lab Biol & Genet Peixes,UNESP, BR-18618000 Botucatu, SP, Brazil Univ Estadual Paulista, UNESP, Dept Zool & Bot, Lab Ictiol, Sao Jose do Rio Preto, SP, Brazil CNPq: 484716-2006-9 CNPq: 306066/2009-2 CNPq: 303854/2009-0 FAPESP: 10/01610-9

Recent investigations in the upper Río Huallaga in Peru revealed the presence of an intriguing species of the Loricariinae. To characterize and place this species within the evolutionary tree of the subfamily, a molecular phylogeny of this group was inferred based on the 12S and 16S mitochondrial genes and the nuclear gene F-reticulon4. The phylogeny indicated that this distinctive species was a member of the subtribe Loricariina. Given its phylogenetic placement, and its unusual morphology, this species is described as a new genus and new species of Loricariinae: Fonchiiloricaria nanodon. This new taxon is diagnosed by usually possessing one to three premaxillary teeth that are greatly reduced; lips with globular papillae on the surface; the distal margin of lower lip bearing short, triangular filaments; the premaxilla greatly reduced; the abdomen completely covered by plates, with the plates between lateral abdominal plates small and rhombic; a caudal fin with 14 rays; the orbital notch absent; five lateral series of plates; dorsal-fin spinelet absent; preanal plate present, large and solid, and of irregular, polygonal shape, the caudal peduncle becoming more compressed posteriorly for the last seven to 10 plates.

Salinity tolerance is one of several important physiological attributes that determine invasion success and the pattern of dispersal of introduced aquatic organisms. Introduced freshwater fishes able to tolerate elevated salinities have the potential to invade and exploit brackish-water (mixohaline) environments and use estuaries and coastal waters as ‘bridges’ for dispersing from one coastal river system to another. Several members of the neotropical suckermouth armoured catfish genus Pterygoplichthys (Siluriformes: Loricariidae) have established non-native populations in inland waters of North and Central America, Asia and islands in the Caribbean, and Pacific and Indian oceans. Loricariids are generally considered to be strictly freshwater; but a few naturally occur in mesohaline habitats. Catch and habitat data from 2004–2005 and 2009–2011 fish surveys in the Grijalva–Usumacinta River delta region (south-eastern Mexico) confirmed that introduced Pterygoplichthys populations established in upstream freshwater sites (where these catfish are abundant) have recently dispersed into downstream oligohaline and mesohaline estuarine habitats. During 2009–2011 surveys, these non-native catfish – tentatively identified as P. pardalis or its hybrids – were found in sites with salinities ranging from 1 to 8 ppt (mean 5.2 ppt). Acute-salinity experiments were conducted with Pterygoplichthys (110–302 mm standard length, N = 140) captured in the Grijalva–Usumacinta Basin to determine upper salinity tolerance levels. Tests demonstrated that individuals maintained in salinities of 0.2 ppt were able to survive abrupt (acute) exposure to salinities up to 10 ppt with little mortality over 10 days (240 h experimental endpoint). A few individuals survived abrupt exposure to 11 and 12 ppt for 20 or more hours, although none survived more than a few hours at 16 ppt or greater. These field and experimental results provide quantitative evidence that non-native Pterygoplichthys are physiologically capable of surviving mesohaline conditions for extended periods and that non-native populations in Mexico are invading and presumably exploiting estuarine and other coastal environments, perhaps as feeding areas and potentially as dispersal routes. Copyright © 2011 John Wiley & Sons, Ltd.

Summary 1. Morphic detritus, including coarse particulate organic matter such as terrestrial tree leaves and wood, is consumed by few fishes in temperate stream systems but is ingested by abundant and diverse groups of specialized fishes in tropical rivers; physiological assimilation and partitioning of morphic detritus by fishes remain poorly understood. 2. This study examines seven species of Neotropical suckermouth-armored catfishes (Loricariidae) that live among and feed on coarse woody debris. Five species represent two unrelated evolutionary lineages showing convergent morphological specializations for gouging into and eating wood, small particles of which fill their guts. Two morphologically distinct species unrelated to wood-eaters and to each other forage along the surface of wood. 3. We examined six jaw functional morphological characteristics of each loricariid species as well as C and N stable isotope ratios of blood plasma, red blood cells and fin tissue of three wood-eating species and muscle tissues of all seven species. Consumer isotopic signatures were compared among species and with isotopic signatures of potential food resources, including biofilm, seston and both bulk wood and holocellulose extracted from bulk wood. 4. Wood-eating species had robust jaws specialized for gouging wood, d 13 C signatures consistent with assimilation of cellulosic wood carbon (not bulk wood carbon or lignin) and elevated d 15 N values (>5AE8&) relative to wood that were consistent with assimilation of N from intermediate microbial decomposers in the environment rather than direct assimilation of N from wood or from endosymbiotic N-fixers. Two non-wood-eating species occupied divergent regions of jaw functional morphospace, and isotopic signatures were consistent with assimilation of C from biofilm and seston, respectively, and N from enriched sources such as microbes, macroinvertebrates or seston. 5. Food resources associated with the surfaces of coarse woody debris in Neotropical rivers are partitioned among at least three guilds of loricariid consumers with divergent jaw morphologies specialized for wood gouging, surface grazing and macroinvertebrate probing. Direct consumption of morphic detritus by specialized Neotropical fishes constitutes a potentially important but poorly understood component of detritus processing and nutrient cycling in tropical rivers.

The present study describes some aspects of the morphology of the digestive tract and the feeding patterns of Loricaria lentiginosa. Sixty-three specimens with gut contents were captured quarterly from November 2001 to August 2002 in Porto Colombia reservoir, Rio Grande basin, southeastern Brazil. The species has bicuspid teeth inserted in the lips, unicuspid teeth in the dentary bone and pharyngeal teeth, besides having short, numerous and slightly separated gill rakers. The stomach is rudimentary and the intestine is relatively short (Intestinal Quotient = 1.32 ± 0.15). Molluscs, especially bivalves, represented the most important item on the diet of this species, followed by organic matter. The characteristics of the digestive tract as well as the dietary pattern, suggest that L. lentiginosa is able to explore bottom food resources, being classified as benthophagous with a tendency to malacophagy, and utilizing organic matter as an associated or additional food resource. Loricariidae species are able to use not only algae, sediment and detritus, but also plant and invertebrate items.

Rineloricaria isaaci is described from tributaries of the Uruguay River basin in Argentina, Brazil and Uruguay. The new species is distinguished by having a long and wide area of naked skin at the snout tip, surpassing the anteriormost pore of the infraorbital ramus of the sensory canal, approximately in the middle of the third postrostral plate, and by its particular sexual dimorphism characterized by the long pectoral and pelvic fins of mature males.

Early life-history stages of the loricariid catfish Ancistrus cf. triradiatus are described, from prehatch embryos to juveniles. The descriptions, as well as metric characters, indicate that the freeswimming embryonic stage is followed directly by the juvenile stage, without a true larval stage or metamorphosis. Intense, but gradual ontogenetic head-shape changes are present during the embryonic and free-living embryonic stages: the suckermouth gradually shifts from an almost rostral to a ventral position. The external and internal transformations related to this shape change are considered an adaptation to both the loricariid algae-scraping feeding mode and the need of suckermouth functioning from the moment of hatching, when a ventrally situated suckermouth would be disadvantageous, as a large yolk sac is present. # 2008 The Authors Journal compilation # 2008 The Fisheries Society of the British Isles

Station holding in Pterygoplichthys spp. was associated with a lower energy cost relative to similarly sized fishes that swam against the free stream current. Pterygoplichthys spp. was characterized by a low, stable mass-specific metabolic rate (c. 50 mg O2 kg−1 h−1) relative to subcarangiform swimmers that held position in the free stream, until it slipped backwards and burst swam against the current. Furthermore, the maximum range of the rate of oxygen consumption (aerobic scope) of Pterygoplichthys spp. was small relative to many non-benthic fishes.

– The population ecology of Ancistrus cryptophthalmus (Reis 1987) was studied by mark–recapture technique in caves from the Sao Domingos karst area, State of Goias, northeastern Brazil. Total population sizes estimated for Angelica and Passa Tres Caves were 20,000 and 1000 individuals, respectively. Densities around 1.0 individuals per m2 in Angelica, Bezerra and Sao Vicente I Streams, and 0.6 individuals per m2 in the smaller Passa Tres Stream may be considered high for cavefish standards, as well as for epigean loricariids. As expected for benthic grazers, cave catfish are highly sedentary. The distribution of size classes did not differ among caves and within the same cave throughout the studied dry seasons; on the contrary, the condition factor decreased throughout this period probably because of the progressive depletion of organic matter available as food. Low proportions of mature individuals, low growth rates (average = 0.5 mm month−1) with cases of negative growth and high longevities (8–10 years) point to a precocial lifestyle, typical of troglobitic species.

Body shape of four distinct populations of Ancistrus cryptophthalmus from different caves in the Sao Domingos karst area and the local epigean (surface) Ancistrus species were compared using geometric morphometrics. Angelica and Bezerra catfishes were closer to each other and successively to the studied sample of epigean catfishes than to Passa Tres and Sao Vicente I catfishes. Greater similarity between catfishes from the Angelica-Bezerra cave system to epigean catfishes than to other cave catfishes may represent a plesiomorphic feature. On the other hand, the present analyses allowed the distinction between Passa Tres and Sao Vicente I catfishes, which inhabited the same cave system. Topographic isolation due to the presence of several waterfalls interposed between the stream reaches where these catfishes live may explain such morphological differentiation. Also, the presence of a waterfall downstream of the reach where the Angelica sample was obtained may have contributed to the partial isolation of these catfishes from those living in Bezerra Cave. Differences in population sizes probably influenced the degrees of morphological differentiation observed among the cave populations. The mosaic distribution of character states indicated that the four populations of A. cryptophthalmus have evolved rather independently, but the continuous variation suggests a recent connection between these populations, perhaps with a limited gene flow. Considering other features such as reduction of eyes and pigmentation, and changes in body shape, a separate species status for the epigean and hypogean Ancistrus species from the Sao Domingos karst area has been maintained.

Tropical South America possesses the largest ichthyofauna of any continental region. To test whether palaeohydrological changes may have been the causes of such diversification, the 'hydrogeological' hypothesis, the phylogenetic relationships of 51 representatives of the catfish genus Hypostomus (Siluriformes: Loricariidae) were inferred using mitochondrial D-loop haplotype sequences. Specimens were collected in all main tropical South American rivers systems east to the Andes. The major interrelationships found with the D-loop data were confirmed with a subset of 21 species using complete internal transcribed spacer (ITS) region sequences. The phylogenetic analysis indicate that the genus Hypostomus can be divided into four monophyletic clades. The historical biogeographical analysis of each of these clades allows the identification of seven major cladogenetic events. Using calibrated D-loop and ITS molecular clocks, date estimations were attributed to each of these cladogenetic events allowing a linkage between four of them with documented hydrogeological changes. Comparisons with published distribution patterns of unrelated fish groups indicate that several of the reconstructed and dated hydrogeological-cladogenetic events may have acted at a large scale on the diversification of Neotropical freshwater fish fauna during late Tertiary.

The questions of whether herbivorous loricariid catfishes are hypometabolic or reduce metabolic demand in response to poor dietary quantity and quality were addressed by comparing resting routine metabolic rates in the presence and absence of different fibre content diets for three loricariid species. Metabolic rates of the three species scaled inter-specifically as body mass 0.736 , similar to most other vertebrates. Metabolic rates did not vary with diet quality for two species; one Panaque species had a significantly lower metabolic rate when fed only wood. Comparisons with the literature led to the conclusions that loricariids in general and Panaque in particular do not have unusually low metabolic rates for quiescent catfishes of their size.

The morphological changes in the gill chloride cells of the armored catfish, Hypostomus tietensis, were investigated after 15 days’ exposure to either distilled or hard water. The thickness of the water–blood barrier in the lamellae increased significantly in fish kept in distilled water due to the high proliferation of chloride cells. The apical surface of about 68% of chloride cells was sharply reduced by the development of an apical crypt with a sponge-like surface, although no change in the chloride cell fractional area was found. In contrast, H. tietensis kept in Na+, Cl− and Ca2+ rich water displayed no significant changes in the number of chloride cells or in their apical surface morphology compared with the control fish. Chloride cell response to ion challenge in H. tietensis suggested the involvement of different strategies to maintain homeostasis in ion-poor water, which may be related to the life history of species.

Most loricariids are algivorous and detritivorous and play an important role in both the grazer and detritus food chains of neotropical waters. Relationships between morphological variation and diet were analysed in six syntopic species (Rhinelepis aspera, Hypostomus regani, H. ternetzi. H. margaritifer, H. microstomus and Megalancistrus aculeatus) fished commercially in a 10 km 2 area of the Upper Parana River upstream from the Itaipu Reservoir. Species feeding on fine grained detritus use suction to obtain food, and possess a well-developed respiratory membrane, long gill rakers, rudimentary labial and pharyngeal teeth, a thin stomach wall, and a long intestine. Species feeding on coarser material (e.g. periphyton), ingest food by scraping the substratum. Their morphological characteristics are large, strong, spatulate teeth, short gill rakers, a well-developed stomach, and a shorter intestine, The first species group is composed by R. aspera while the latter by M. aculeatus and H. microstomus. The others species had an intermediary position.

— Seasonal observations in the gonadosomatic index and development stages of female ovaries showed that Hypostomus luetkeni has an extended spawning period lasting from September to February. Histological examinations and analysis of oocyte size distributions indicated a fractional spawning. Fecundity was determined in ripe ovaries and indicated that H. luetkeni, as most other Loricariidae, spawn a small number (446-936 eggs-ind−1) of large eggs (5.2 mm).

The stomach contents of 24 species of fish and unidentified species from four genera in a floodplain lake of the Pantanal were studied. Fish were collected during the dry season when the lake was isolated from the main river. A community food ingestion index (feeding index weighted by consumer biomass, FIWCB, where 0 < FIWCB < 1) was calculated to quantify feeding patterns. Detritus and algae ingested by Curimatidae were responsible for 46.5% of the FIWCB, while that for algae ingested by Loricariidae (armoured catfish) accounted for 13.2%. The importance of detritus in fish diets is discussed as a strategy for shortening food chains, thereby increasing community efficiency, and as a consequence, fish biomass. It was learnt that the main route of energy flow in this perennial lake was through the detritus chain. The floodplain lakes function as a dry season feeding ground for small-sized species of fish, which are potential prey for the more highly valued larger species of fish.

Armored catfish (Loricariidae) are the major grazers of attached algae in pools of the Rio Frijoles, Panama (909' N, 79044' W). In the dry season, sunny pools were inhabited by -6 individual loricariids per square metre of grazeable substratum. At these densities, armored catfish depleted algae and cleared sediment from bedrock substrata, leaving sparse standing crops of small, adnate diatoms (primarily Achnanthes spp.). To study the effects of armored catfish at 1/6 their natural density, I stocked four 6-7 cm (SL), 10-g Ancistrus (the most common size class of the most common species in stream pools) in each of five stream pens. Pens enclosed 4 m2 of bedrock substratum, and were alternately stocked or left empty during three consecutive periods of 29, 11, and 11 d. At the end of each period, standing crops of sediment and attached algae, and rates of photosynthesis by attached algae, were measured. The attached algae that developed with sparse Ancistrus had higher standing crops with larger cells or colonies, and higher primary productivity, than did periphyton subjected to heavy grazing by unconfined armored catfish. Even heavy grazing, however, was less deleterious to attached algae than prolonged sedimentation on substrata in enclosures left empty for 11 or 29 d. The net effect of Ancistrus on their algal food changed from depletion at high grazer densities to enhancement at low grazer densities, as sedimentation became more limiting to algae than grazing.

Four species of armored catfish (Loricariidae) have size-specific depth distributions in a Panamanian stream, with larger fish in deeper water. Depth distributions do not change from the dry to the rainy season, despite a two- to three-fold increase in habitat area for larger loricariids. Throughout the year, standing crops of the loricariids' attached algal food are relatively high in shallow water, but decrease rapidly with depth. Over 21/2 yr, large Ancistrus spinosus, the most common pool- dwelling loricariid, showed significant seasonal changes in somatic growth rates, with maximum rates in the early rainy season and minimum rates in the late dry season. Significant seasonal changes in mortality rates, estimated from rates of disappearance of marked individuals, were not detected. These data are consistent with the following hypothesis: small loricariids are limited, perhaps by predation, at densities below those necessary to deplete algae in shallow water. Larger loricariids avoid shallow water where they are vulnerable to fishing birds, even in the dry season when food is in short supply in deeper areas.

A detailed description of the head skeleton of Sisor rabdophorus Hamilton is given. It has been shown that in general the skull conforms to the normal siluroid pattern and in particular shares most of the characteristic features of the family Sisoridae. It is, however, highly specialized for sluggish bottom life and shows certain unique features not only among sisorids but all Indian siluroids, e. g. the movable articulation of the premaxillae with the ethmoid (a character shared with most highly specialized South American families, Loricariidae and Callichthyidae) and their edentulous nature; the small and edentulous nature of dentaries, etc.

The catfish (Siluroidei) appear to have evolved from an ancestor which, in most respects other than the form of its teeth, resembled primitive Characinoidei. In the first part of this paper it is shown that most of the numerous and profound anatomical changes which have occurred in the course of their evolution from this ancestor can be related to one or other of three basic changes: depression of the body in adaptation to bottom-feeding habits, sensory modification in adaptation to nocturnal habits, and the evolution of defensive fin spines. Diplomystes is more primitive than other known catfish in the form of its maxilla and pectoral girdle, and in the posterior position of its dorsal fin. The second part of the paper is concerned with some of the more specialized families of catfish (Mochokidae, Siluridae, Schilbeidae, Malapteruridae, Clariidae, Callichthyidae and Loricariidae). The specializations in each case are described, and related to the habits of the fish.

The Weberian apparatus of Siluri with fully developed swimbladders is described. and comparisons are made with the Cyprini. Special attention is paid to the histology of the soft parts. The reduced encapsulated swimbladders of Clarias, Plecostomus (Loricariidae) and Hoplostemum (Callichthyidae) are described, and the homologies of the parts of their capsules and the mechanisms of their Weberian apparatus considered. It is suggested that reduction of the swimbladder in such forms is in adaptation to life on the bottom or in compensation for the hydrostatic effect of accessory respiratory organs, and that encapsulation is due to the bony parts concerned not being correspondingly reduced.

A detailed description of the vertebral column, median fin skeleton and musculature is given. Comparisons based on the study of these structures in Gagata and Loricaria have been made. It has been clearly demonstrated that these structures in Sisor bear an unmistakable imprint of the bottom-living habit of the fish and as such show a remarkable series of convergent modifications with the most highly specialized catfish family, Loricariidae, while Gagata shows an intermediate stage between the typical siluroid condition and the extreme type of modifications found in Sisor and Loricaria. That Sisor diverged early from the main stem of sisorid evolution is further supported by this study.