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Batrochoglanis labrosus new species, is described from the Capim River Basin, State of Pará, Brazil. The new species differs from congeners by the stout, inferior mandible, hypertrophied lips on the lateral of the mouth, a broad dark brown band extending dorsoventrally from the beginning of the trunk to the posterior third of the adipose fin followed by a second dark brown band on the caudal peduncle, dark brown pelvic fin, and caudal fin hyaline with a concentration of dark brown spots on the posterior margin, sometimes forming an irregular band. The morphometric variables of B. labrosus are similar in B. villosus and B. castaneus, forming a B. villosus species group. The B. villosus group is distinct from other group formed by B. acanthochiroides and B. transmontanus in the third axis of the Principal Components Analysis. The variables with higher positive loadings in the B. villosus group, representing larger measurements, were adipose-fin base length, eye diameter, maxillary barbel length, head depth, and mouth width; the higher negative loadings representing shorter measurements were pelvic fin to anal fin distance and pectoral-fin spine length. The species is known only from the Capim River basin, where it is possibly endemic.

Rhyacoglanis pulcher is a rare Neotropical rheophilic bumblebee catfish known only from the type locality in the Cis-Andean Amazon region, Ecuador, and the type-species of the genus. So far, the three syntypes collected in 1880 were the only specimens unambiguously associated to the name R. pulcher available in scientific collections. Recently, a specimen was discovered in a fast-flowing stretch of the Villano river, a tributary of the Curaray river, Napo river basin, Ecuador, representing a new record after nearly 140 years. Here, we present this new record, identified by morphology, provide the DNA barcode sequence of the specimen, and propose why the species of Rhyacoglanis are scarce in zoological collections. Additionally, we discuss the intraspecific variation in the color pattern observed in R. pulcher., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Chuctaya et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large-scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications., (© 2022 The Ecological Society of America.)

The wide distribution of the Neotropical freshwater catfish Rhamdia offers an excellent opportunity to investigate the historical processes responsible for modeling South America's hydrogeological structure. We used sequences from cis-Andean and Mesoamerican Rhamdia species to reconstruct and estimate divergence times among cis-Andean lineages, correlating the results with known geological events. Species delimitation methods based on distance (DNA barcoding and BIN) and coalescence (GMYC) approaches identified nine well-supported lineages from the cis-Andean region from sequences available in the BOLD dataset. The cis-Andean Rhamdia lineages diversification process began in Eocene and represented the split between cis-Andean and Mesoamerican clades. The cis-Andean clade contains two principal groups: Northwest clade (MOTUs from Amazon, Essequibo, Paraguay, and Itapecuru basins) and Southeast clade (Eastern Brazilian shield basins (Paraná, Uruguay, Iguaçu, and São Francisco) plus eastern coastal basins). The diversification of the cis-Andean Rhamdia lineages results from vicariance and geodispersion events, which played a key role in the current intricate distribution pattern of the Rhamdia lineages. The wide geographical distribution and large size of the specimens make it attractive to cultivate in different countries of the Neotropical region. The lineages delimitation minimizes identification mistakes, unintentional crossings by aquaculture, and reduces natural stocks contamination.

The fish fauna from the Lower Iguaçu River and tributaries upstream of the Iguaçu Falls, the last free-flowing river stretch, were investigated. Twenty five sites in tributaries and the main channel were sampled between 2010 and 2016 using several kinds of fishing gear. The species were categorized according to their size, origin, and conservation status. Species richness and abundance in the main channel and tributaries were compared. In total, 87,702 specimens were recorded, comprising 76 species, 25 families, 53 genera, and eight orders. Characiformes and Siluriformes were the richest orders, representing 92% of the total specimens; Characidae, Cichlidae, Pimelodidae, and Loricariidae were the richest families. The fish fauna was composed of small and medium-sized species and included endemic (42%), autochthonous (24%), allochthonous (21%), and exotic (9%) species, as well as hybrids (4%). Significant differences in the relative numerical abundance of species were found among sites. Ancistrus mullerae and Rhamdia branneri (endemic) were indicator species for tributaries inside of Iguaçu National Park (INP), while Phalloceros harpagos (autochthonous) and Ictalurus punctatus (exotic) for tributaries outside of INP and Odontesthes bonariensis (allochthonous) for the main channel. The last dam-free stretch of the Lower Iguaçu River and tributaries upstream the Iguaçu Falls exhibits a rich endemic fish fauna, including some rare, endangered species ( Steindachneridion melanodermatum , Gymnogeophagus taroba , and Psalidodon gymnogenys ). These findings are essential to predict and understand the effects caused by the new Baixo Iguaçu Hydroelectric Power Plant and highlight the importance of tributaries and Iguaçu National Park for conservation of endemic species., (Suelen Fernanda Ranucci Pini, Maristela Cavicchioli Makrakis, Mayara Pereira Neves, Sergio Makrakis, Oscar Akio Shibatta, Elaine Antoniassi Luiz Kashiwaqui.)

The gross brain morphology and the peripheral olfactory organ of Microglanis garavelloi are described throughout development, and the relationship of these organs to the general behaviour of the species is discussed. During the development, the main brain subdivisions undergo a series of morphological changes keeping a relatively constant volume increase. However, we observed different growth rates in the brains of males and females when these were compared. During the maturation process, a series of hormonal events result in the development of some secondary sexual traits in the brain of male specimens, like faster growth rate of brain areas linked to motor control, olfactory and visual responses. The number of olfactory-organ lamellae increases continuously in both males and females, during their maturation period. These results suggest that changes may be caused by cognitive demands that this species is exposed to throughout its lifespan. The gross morphological arrangement of the central nervous system indicates shared patterns with other members of the family Pseudopimelodidae., (© 2021 Wiley Periodicals LLC.)

A new species, Batrochoglanis castaneus, is described from the Aripuanã River basin, Brazil. It differs from congeners, except B. raninus and B. transmontanus, by the dark brown color of the body and a dark brown stripe on the caudal fin. The new species differs from B. raninus by the longer maxillary barbel, longer prepelvic length, greater prepectoral length, smaller anal-fin base length, and smaller head depth. The new species differs from B. transmontanus by the longer caudal-fin dorsal lobe, presence of a hyaline spot or stripe on pelvic, dorsal, and anal fins, longer maxillary barbel, longer pectoral-fin, and dorsal-fin spines, greater eye diameter, smaller head depth, and larger mouth width. A metapterygoid anteriorly bifurcated and the lateral line reaching the adipose fin present in the new species are interpreted as synapomorphies of Batrochoglanis. On the other hand, the distribution of pore and neuromasts of the laterosensory system of the head seems to be very conservative in the family. The new species is known only from the Aripuanã River basin, reinforcing its characteristics as an area of endemism for fishes in the Amazon basin.

Environmental heterogeneity is a factor which can help explain the higher local species richness. The objective of this study was to test if richness and composition of anurans species are related to available microhabitats and landscape type of sampled sites. We assume that a higher number of microhabitats increase environmental heterogeneity and this, in turn, affects species richness of amphibians. We performed the study in the Mesophytic Semideciduous Forest, a vegetation type within Atlantic Forest Domain. Between October 2010 and February 2011, we sampled 23 water bodies located in the agricultural, forest, and urban landscapes. The species richness was determined using survey at breeding sites methodology, and the availability of microhabitats was estimated visually. Thirty-four anuran species belonging to 12 families were recorded. The species richness in water bodies ranged from two to 13 species. The highest species richness was recorded in environments with a higher number of microhabitats, while the species composition in water bodies was partially grouped according to the predominant landscape type that is agricultural, forest, forest edge or urban. Our results suggest that species use specific environments (e.g. landscapes, habitat and microhabitat) for their reproductive activities.

The southern region of Brazil is characterized by high species diversity and endemism of freshwater fishes distributed across geographically isolated river basins. Microglanis cottoides has a widespread range across these river basins and occurs in sympatry with other endemic species of the genus (e.g. M. cibelae, M. eurystoma, and M. malabarbai). Herein we tested the monophyly of M. cottoides and presented for the first time information about the molecular phylogeny of species in the genus. The results suggest that M. cottoides currently forms a non-monophyletic group which includes populations endemic to the Uruguay River basin that are more closely related to M. malabarbai, and excludes M. cibelae, found to be nested within M. cottoides. Based on an integrative approach using morphological and molecular data, we propose M. cibelae as a junior synonym of M. cottoides, and the populations of the Uruguay River basin previously assigned to M. cottoides in fact belong to M. malabarbai. Our molecular phylogeny shows that M. cottoides is sister to M. parahybae, which is also a coastal species, and M. malabarbai is sister of M. garavelloi, both endemic to inland river basins. The time-calibrated phylogeny indicates that the separation between inland and the coastal clades occurred in the Tertiary period, and that the species within the coastal basins diverged in the Pliocene, which overlaps with the diversification times estimated for the two inland species as well. This pattern of diversification corroborates some previous studies with other fishes from the same region., Competing Interests: The authors have declared that no competing interests exist.

Gymnogeophagus setequedas is a rare and rheophilic species of tribe Geophagini, considered endangered in Brazilian red lists. Its previously known geographical distribution range was the Paraná River basin, in Paraguay, and a tributary of the Itaipu Reservoir in Brazil. Since its description no specimens have been collected in the original known distribution area. However, recent records of G. setequedas in the lower Iguaçu River, in a region considered highly endemic for the ichthyofauna, extended the known geographical distribution and may represent one of the last remnants of the species. The aim of this study was to estimate the genetic diversity and population structure of G. setequedas , using microsatellite markers and mitochondrial haplotypes, in order to test the hypothesis of low genetic diversity in this restricted population. Muscular tissue samples of 86 specimens were obtained from nine locations in the Lower Iguaçu River basin, between upstream of the Iguaçu Falls and downstream of the Salto Caxias Reservoir. Seven microsatellites loci were examined and a total of 120 different alleles were obtained. The number of alleles per locus ( N A ) was 17.429, effective alleles ( N E ) 6.644, expected heterozygosity ( H E ) 0.675, observed ( H O ) heterozygosity 0.592, and inbreeding coefficient ( F IS ) 0.128. Twelve haplotypes in the D-Loop region were revealed, with values of h (0.7642) and π (0.00729), suggesting a large and stable population with a long evolutionary history. Thus, both molecular markers revealed high levels of genetic diversity and indicated the occurrence of a single G. setequedas population distributed along a stretch of approximately 200 km. The pattern of mismatch distribution was multimodal, which is usually ascribed to populations in demographic equilibrium. Nevertheless, the construction of a new hydroelectric power plant, already underway between the Salto Caxias Reservoir and Iguaçu Falls, could fragment this population, causing loss of genetic diversity and population decline, and for this reason it is necessary to maintain the Iguaçu River tributaries and downstream area from the Lower Iguaçu Reservoir free of additional dams, to guarantee the survival of this species.

Pseudopimelodidae are Neotropical catfishes characterized by having slightly to strongly depressed body in fully developed specimens. The largest species of the family with 500 mm SL, Lophiosilurus alexandri, experiences impressive changes in body shape during development, becoming extremely depressed when fully developed. Accordingly, Lophiosilurus alexandri is an ideal species to observe the morphological changes during ontogeny, and to seek solid interpretations on the polarity of characters. Specimens of distinct larval periods (yolk sac, flexion and postflexion; n = 186 specimens) and juvenile stages (n = 20) were analyzed. Changes in body shape, position of mouth and eye, morphology of fins and pigmentation were observed during the development of Lophiosilurus. Larvae (5.7-11.2 mm standard length) had pigmentation concentrated on the head and parts of body, eyes small and pigmented, short barbels, and well-developed finfold. Juveniles (15.9-28.1 mm standard length) had body shape similar to adult, with head depressed and bearing bony ridges, large mouth, dorsally-oriented eyes, small barbels and well-developed shoulder bulges (cleithral width). The greatest morphological changes in the development of L. alexandri occurred during the postflexion larval stage. Relative to standard length, measurements of snout length, head depth and body depth are smaller in juveniles than in larvae, but body width is larger. New interpretations on the phylogenetic characters related to these changes are provided in view of the two alternative hypotheses of the evolution of Pseudopimelodidae.

The gross morphology of the gas bladder is described and compared for representatives of all valid genera of Pseudopimelodidae (Siluriformes). Cephalosilurus albomarginatus and species of Batrochoglanis, and Microglanis have the most basic form: a large, cordiform gas bladder with a simple internal T-shaped septum. Cephalosilurus apurensis, C. fowleri, and C. nigricauda also have a large, cordiform gas bladder, but they have well-developed trabeculae associated with the internal T-shaped septum, and a pair of well-developed constrictor muscles inserted on the external wall; the latter feature is present in most species of Pimelodidae, but absent in all other catfishes. The monotypic Lophiosilurus alexandri also has well-developed constrictor muscles, and its gas bladder is moderately sized. The species of Pseudopimelodus and Cruciglanis have a diminutive gas bladder partially divided into two lateral sacs without internal communication, and lack constrictor muscles. The parapophysis of the fourth vertebra is a wide and long shelf connected to the dorsal surface of the gas bladder in most pseudopimelodid genera. However, in the species of Pseudopimelodus and Cruciglanis the parapophysis of the fourth vertebra is shorter and has its anterior ramus folded back, partially covering the gas bladder anteroventrally; and the tympanic opening is smaller than in species of the other genera. Five phylogenetic characters are proposed based on the morphology of the gas bladder and associated structures in species of Pseudopimelodidae, and the evolution of those characters in the family is discussed. J. Morphol., 2011. © 2011 Wiley-Liss, Inc., (Copyright © 2011 Wiley-Liss, Inc.)

Cytogenetic and morphometric analyses were carried out in Hoplias aff. malabaricus specimens from six distinct populations from the lower Paranapanema River basin, located between the states of Paraná and São Paulo, Brazil. Measurements were also taken from a specimen collected in Surinam. In a population from a fish farm station at Universidade do Norte do Parana (EPUNOPAR), two sympatric cytotypes (2n = 40 and 2n = 42 chromosomes) are found. A population from a fish farm station at Universidade Estadual de Londrina (EPUEL) shows 2n = 42 meta-submetacentric chromosomes for males and females with a simple sex chromosome system of XX/XY type. Populations from the Vermelho and Rancho Alegre Rivers, Três Bocas Stream and Paranapanema River have 2n = 39 chromosomes in males and 2n = 40 chromosomes in females, showing a multiple sex chromosome system of X(1)X(1)X(2)X(2)/X(1)X(2)Y type. Twenty morphological variables were studied. These measurements were used for an analysis of the canonical variables and standard analysis of proportional measurements. The most variable measurements among the specimens are the maxilla length (MXL) and the pre-dorsal distance (PDD). Analysis of canonical variables indicates three distinct groups in the first canonical axis formed by: (1) Três Bocas Stream, (2) Rancho Alegre + Vermelho River + EPUNOPAR and (3) EPUEL + Paranapanema River. This axis retained 79.4% of information from the original matrix. Analysis of morphometrics reveals differences among populations from the Paranapanema River basin and between these and the specimen from Surinam. The morphometric and cytogenetic differences among the studied populations suggest a species complex.