A new species of Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae) from the rio Tocantins-Araguaia basin, Brazil

Hypostomus delimai is described from the rio Tocantins, Tocantins State, and from the rio Araguaia, Pará, and Tocantins States, Brazil. The new species is distinguished from all other Hypostomus species, except from H. carinatus, H. hoplonites, and H. watwata, by the presence of five to eight (mode seven) predorsal plates limiting posterior border of the supraoccipital bone (vs. one to three plates). It can be distinguished from H. carinatus, H. hoplonites, and H. watwata by having pale spots over darker background on body and fins (vs. dark spots over lighter background). The species was only found in the middle stretches of the rio Tocantins-Araguaia basin. The first collection of specimens assigned to the new species was done in the rio Tocantins before the construction of the Tucuruí dam. Recently additional material was collected in the rio Araguaia, in a habitat that soon will be flooded for the construction of the Santa Isabel hydroelectric power station. © 2013 Sociedade Brasileira de Ictiologia

Karyotype description of three species of Loricariidae (Siluriformes) and occurrence of the ZZ/ZW sexual system in Hemiancistrus spilomma Cardoso & Lucinda, 2003

The neotropical freshwater systems have a high number of catfish species (Siluriformes), and many of those are denominated "cascudos" in Brazil. Cytogenetic data about three "cascudos" species fished in the rio Araguaia are described in the present study. The Pterygoplichthys joselimaianus showed 2n=52, with 28 metacentrics (M) chromosomes, 16 submetacentrics (SM) and 8 subtelocentrics/acrocentrics (ST/A) in both sexes. Hemiancistrus spinosissimus showed 2n=52, with karyotype formulae 26M+22SM+4ST, in both sexes. Hemiancistrus spilomma also showed 2n=52, but in this species a ZZ/ZW sex chromosome system (25M+21SM+6ST in females and 24M+22SM+6ST in males) was observed. The cells from H. spinosissimus and P. joselimaianus showed one chromosome pair bearing Ag-NORs, while in the H. spilomma three chromosome pairs bearing Ag-NORs were detected. The data showed in this work reveal particular chromosomal characteristics, important for a good recognition of both Hemincistrus species, and also show the importance of the insertion of cytogenetic data on taxonomic phylogenetic studies. Copyright © 2006 Sociedade Brasileira de Ictiologia

Two new ornamental loricariid catfishes of Baryancistrus from rio Xingu drainage (Siluriformes: Hypostominae)

Two new species of the hypostomine genus Baryancistrus are described from the rio Xingu drainage. Baryancistrus xanthellus is distinguished from all other Baryancistrus species by the presence of yellow spots along the entire body and conspicuous yellow marks on distal tip of dorsal and caudal fins. Baryancistrus chrysolomus is distinguished from its congeners by its uniform dark body coloration and presence of yellow bands on dorsal and caudal fins. Despite the lack of formal description, these species are very popular in the international aquarium trade. We expect that these formal descriptions might contribute to the improvement of Brazilian regulations in the international trade of ornamental loricariids. © 2011 Sociedade Brasileira de Ictiologia

A new species of Ancistrus Kner, 1854 (Siluriformes: Loricariidae) from rio Madeira basin, Amazonas State, Brazil

During the Mosaico do Apuí expedition in 2006, a new species of Ancistrus was found in the rio Sucunduri, a large tributary of the rio Madeira basin in south Amazonas State. The new species has a unique color pattern for the genus and is distinguished by the presence of alternate light and dark vertical bars on the trunk. Other Ancistrini genera have species with a similar color pattern, but the new species is clearly distinguished by a lack of plates on the snout and presence of fleshy tentacles on the snout as in all Ancistrus representatives. We also provide comments on the taxonomic status of the A. bolivianus, A. heterorhynchus and A. marcapatae. © 2019 Sociedade Brasileira de Ictiologia. All Rights Reserved

Karyotype characterization and ZZ/ZW sex chromosome heteromorphism in two species of the catfish genus Ancistrus Kner, 1854 (Siluriformes: Loricariidae) from the Amazon basin

We present karyotypic characteristics and report on the occurrence of ZZ/ZW sex chromosomes in Ancistrus ranunculus (rio Xingu) and Ancistrus sp. "Piagaçu" (rio Purus), of the Brazilian Amazon. Ancistrus ranunculus has a modal number of 2n=48 chromosomes, a fundamental number (FN) of 82 for both sexes, and the karyotypic formula was 20m+8sm+6st+14a for males and 19m+9sm+6st+14a for females. Ancistrus sp. "Piagaçu" presented 2n=52 chromosomes, FN=78 for males and FN=79 for females. The karyotypic formula was 16m+8sm+2st+26a for males and 16m+9sm+2st+25a for females. The high number of acrocentric chromosomes in karyotype of Ancistrus sp. "Piagaçu" differs from the majority of Ancistrini genera studied so far, and may have resulted from pericentric inversions and translocations. The lower number of chromosomes in A. ranunculus indicates that centric fusions also occurred in the evolution of Ancistrus karyotypes. We conclude that karyotypic characteristics and the presence of sex chromosomes can constitute important cytotaxonomic markers to identify cryptic species of Ancistrus. However, sex chromosomes apparently arose independently within the genus and thus do not constitute a reliable character to analyze phylogenetic relations among Ancistrus species. Copyright © 2007 Sociedade Brasileira de Ictiologia

Unexpected species diversity in electric eels with a description of the strongest living bioelectricity generator

Is there only one electric eel species? For two and a half centuries since its description by Linnaeus, Electrophorus electricus has captivated humankind by its capacity to generate strong electric discharges. Despite the importance of Electrophorus in multiple fields of science, the possibility of additional species-level diversity in the genus, which could also reveal a hidden variety of substances and bioelectrogenic functions, has hitherto not been explored. Here, based on overwhelming patterns of genetic, morphological, and ecological data, we reject the hypothesis of a single species broadly distributed throughout Greater Amazonia. Our analyses readily identify three major lineages that diverged during the Miocene and Pliocene—two of which warrant recognition as new species. For one of the new species, we recorded a discharge of 860 V, well above 650 V previously cited for Electrophorus, making it the strongest living bioelectricity generator. © 2019, The Author(s)

Diversidade cariotípica entre dez espécies do gênero Ancistrus (Siluriformes, Loricariidae) da Bacia Amazônica: estrutura e mecanismos de evolução cromossômica

The tribe Ancistrini belongs to the subfamily Hypostominae (Siluriformes: Loricariidae). Phylogenetic studies of this group of fishes are few, leaving their systematics relatively unknown. Ancistrus, the type genus of the Ancistrini tribe, contains 53 valid species and at least six Amazonian species that have yet to be described. In order to explore mechanisms of chromosome evolution in the genus Ancistrus, we studied 10 species collected from locations across the Amazon basin. We found a large karyotypic diversity among the ten species, in both macrostructure (chromosome number and formula) and pattern of nucleolar organizer regions and constitutive heterochromatin. The diploid number varied between 34 and 52 chromosomes and the number of arms varied between 68 and 82. The RON varied in both chromosome location (terminal, interstitial, long arm, short arm) and karyotype position. Few chromosomes presented constitutive heterochromatin; when present, this heterochromatin was distributed in discrete blocks in the centromeric position, terminal or interstitial. The occurrence of low diploid numbers suggests the presence of centric fusions in the chromosomal evolution of this group. Besides documenting karyotypic diversity, we also studied the sex chromosome systems of seven of the 10 species. We found two cases of ZZ/ZW, three cases of XX/XY, and two multiple systems: XX/XY1Y2 and Z1Z1Z2Z2/Z1Z2W1W2. Fish of the genus Ancistrus exhibit low vagility, territoriality and parental care. These ethological characteristics may create a gene flow barrier among populations, allowing microallopatric speciation and resulting in the large karyotypic diversity found in these species.A tribo Ancistrini pertencente à subfamília Hypostominae (Siluriformes: Loricariidae), compõe um grupo de peixes cuja sistemática é ainda pouco conhecida e estudos filogenéticos são escassos. Ancistrus, gênero tipo da tribo Ancistrini, engloba 53 espécies válidas e pelo menos seis espécies amazônicas ainda não descritas. Com o objetivo de verificar os mecanismos de evolução cromossômica existentes em espécies pertencentes ao gênero Ancistrus, foram estudadas dez espécies provenientes de diversos pontos da bacia amazônica. As análises revelaram uma grande diversidade cariotípica, tanto na macroestrutura (número e fórmula cromossômica) como também nos padrões de regiões organizadoras de nucléolos e de heterocromatina cons titutiva. O número diplóide variou de 34 a 52 cromossomos e o número de braços de 68 a 82. A RON variou tanto na localização no cromossomo (terminal, intersticial, braço longo e braço curto) como na posição no cariótipo. Poucos cromossomos apresentaram heterocromatina constitutiva, as quais foram distribuídas em blocos discretos dispostos em posição centromérica, terminal ou intersticial. A ocorrência de números diplóides baixos (menor que 52) sugere a presença de fusões cêntricas na evolução cromossômica deste grupo. Além da diversidade cariotípica, sistemas de cromossomos sexuais foram registrados para sete das 10 espécies analisadas sendo: duas ZZ/ZW, três XX/XY e dois sistemas múltiplos XX/XY1Y2 e Z1Z1Z2Z2/Z1Z2W1W2. Peixes do gênero Ancistrus exibem baixa vagilidade, territorialismo e cuidado parental. Estas características etológicas podem criar uma barreira ao fluxo gênico entre populações, permitindo especiações micro-alopátricas e resultando na grande diversidade cariotípica encontrada nestas espécies

Sistemática de Baryancistrus Rapp Py-Daniel, 1989 (Loricariidae: Hypostominae)

The main objectives of the present thesis were to provide a taxonomic review of the genus Baryancistrus, to assess the phylogenetic relationships within the genus, to check its monophyly and to understand the phylogenetic position of the genus within the tribe Ancistrini. The current species included in Baryancistrus were revised based on examination of type material, topotypes, specimens deposited in several fish collections and original descriptions. A phylogenetic hypothesis is proposed for the relationships of the genera of Ancistrini and for the species of Baryancistrus based on 192 characters of 110 terminal taxa. Four of the six species already proposed for the genus were accepted plus the recognition of more 10 new species. An identification key is presented for all species recognized in the genus after the taxonomic revision. Baryancistrus was restricted to the clear-water rivers of the Amazon basin that drain the Guiana and Brazilian Shields. Parsimony analyses resulted in 48 equally most parsimonious trees with 1,704 steps, consistency index of 0.16 and retention index of 0.67; strict-consensus tree was rooted in Rhinelepis strigosa. Baryancistrus were recovered as a natural group, excluding the ones from rio Orinoco basin, in Venezuela. Monophyly of Baryancistrus was supported by 12 non-exclusive synapomorphies, and the most relevant are the thick and round condyle of the quadrate for articulation with the angulo-articular, the presence of a deep depression on the posterior tip of the opercle, elongate maxillary and the presence of seven to eigth infraorbitals. The 14 species of the genus were grouped as (Baryancistrus sp. “membrana” (Baryancistrus sp. “Jari” ((Baryancistrus sp. “Trombetas” (B. longipinnis, B. niveatus)) ((Baryancistrus sp. “jolie” (Baryancistrus sp. “Tapajos”, B. xanthellus))) ((B. chrysolomus (Baryancistrus sp. “Teles Pires”, Baryancistrus sp. “Porteira”)) ((Baryancistrus sp. “bola branca” (Baryancistrus sp. “Araguaia”, Baryancistrus sp. “Culuene”))))), comprising the sister-group of the remaining Ancistrini with hypertrophied membrane posterior to the last dorsal fin ray. Relationships of the genera within Ancistrini are discussed with the proposition of revalidation of previously synonymized genera and new taxonomic arrangements.Os principais objetivos da presente tese foram fornecer uma revisão taxonômica de Baryancistrus, avaliar as relações filogenéticas dentro do gênero, verificar seu monofiletismo e entender a posição filogenética do gênero dentro da tribo Ancistrini. As atuais espécies incluídas em Baryancistrus foram revisadas com base no exame do material tipo, topótipos, espécimes depositados em várias coleções de peixes e descrições originais. Uma hipótese de relações filogenética entre os gêneros de Ancistrini e entre as espécies de Baryancistrus é apresentada com base em 192 caracteres de 110 táxons terminais. Quatro das seis espécies já propostas para o gênero foram aceitas, mais o reconhecimento de mais 10 espécies novas. Uma chave de identificação é apresentada para todas as espécies reconhecidas no gênero após a revisão taxonômica. Baryancistrus ficou restrito aos rios de águas claras oriundos da bacia Amazônica brasileira que drenam os escudos da Guiana e do Brasil. A análise de parcimônia resultou em 48 árvores igualmente parcimoniosas, com 1.704 passos, índice de consistência 0,16 e índice de retenção 0,67; a árvore de consenso estrito foi enraizada em Rhinelepis strigosa. Baryancistrus foi recuperado como um grupo natural, quando excluindo as espécies descritas anteriormente para o gênero, oriundas da bacia do rio Orinoco, na Venezuela. O monofiletismo de Baryancistrus foi suportado por 12 sinapomorfias não-exclusivas, e as mais relevantes são, o côndilo de articulação do quadrado com o ângulo-articular grosso e redondo, a presença de uma fóvea profunda na extremidade posterior do opérculo, o maxilar muito alongado, e a presença de sete a oito infraorbitais. As 14 espécies do gênero foram agrupadas como: (Baryancistrus sp. “membrana” (Baryancistrus sp. “Jari” ((Baryancistrus sp. “Trombetas” (B. longipinnis, B. niveatus)) ((Baryancistrus sp. “jolie” (Baryancistrus sp. “Tapajos”, B. xanthellus))) ((B. chrysolomus (Baryancistrus sp. “Teles Pires”, Baryancistrus sp. “Porteira”)) ((Baryancistrus sp. “bola branca” (Baryancistrus sp. “Araguaia”, Baryancistrus sp. “Culuene”))))), compreendendo o grupo-irmão dos demais Ancistrini que apresentam membrana hipertrofiada posterior ao último raio da nadadeira dorsal. Os relacionamentos dos gêneros dentro de Ancistrini são discutidos com a proposta de revalidação de gêneros previamente sinonimizados e novos arranjos taxonômicos

A new species of Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae) from the rio Tocantins-Araguaia basin, Brazil

Hypostomus delimaiis described from the rio Tocantins, Tocantins State, and from the rio Araguaia, Pará, and Tocantins States, Brazil. The new species is distinguished from all other Hypostomusspecies, except from H. carinatus, H. hoplonites, and H. watwata, by the presence of five to eight (mode seven) predorsal plates limiting posterior border of the supraoccipital bone (vs. one to three plates). It can be distinguished from H. carinatus, H. hoplonites, and H. watwata by having pale spots over darker background on body and fins (vs. dark spots over lighter background). The species was only found in the middle stretches of the rio Tocantins-Araguaia basin. The first collection of specimens assigned to the new species was done in the rio Tocantins before the construction of the Tucuruí dam. Recently additional material was collected in the rio Araguaia, in a habitat that soon will be flooded for the construction of the Santa Isabel hydroelectric power station