First record and extended distribution of Otothyropsis piribebuy (Loricariidae: Hypoptopomatinae) in Brazil

Cascudinhos are a group of small benthic fishes included in the Hypoptopomatinae subfamily, inhabiting small to moderate streams and rivers within the Neotropical region, from Venezuela to Northern Argentina. Until now, Otothyropsis piribebuy originally described from the rio Paraguay basin, in Paraguay, is the only species of the genus not recorded in Brazil. Recent samples in the rio Tererê, rio Paraguay basin, Brazil, revealed a population of Otothyropsis with uncertain taxonomic identity. Therefore, the study aimed to unveil the distribution of Otothyropsis within Brazilian territory. External morphology, osteology, measurements, and counts (plates, teeth, and rays) of these specimens from rio Tererê were compared to data from the original description of O. piribebuy, and also with specimens of O. piribebuy sampled in Paraguayan territory. Observations indicated no differences among the analyzed specimens. Furthermore, a Principal Component Analysis (PCA), carried out using log-transformed measures from Brazilian and Paraguayan specimens, showed no separation of these populations, also indicating that all analyzed specimens pertain to the same species. Based on this, a prediction map of distribution, using Maximum Entropy, was produced. The correct identification of spatial range of occurrence is an essential step to ensure the conservation of species, and the extended distribution of Otothyropsis piribebuy was confirmed, enhancing the list of neotropical fish from Brazil.

First record and extended distribution of Otothyropsis piribebuy (Loricariidae: Hypoptopomatinae) in Brazil

Abstract Cascudinhos are a group of small benthic fishes included in the Hypoptopomatinae subfamily, inhabiting small to moderate streams and rivers within the Neotropical region, from Venezuela to Northern Argentina. Until now, Otothyropsis piribebuy originally described from the rio Paraguay basin, in Paraguay, is the only species of the genus not recorded in Brazil. Recent samples in the rio Tererê, rio Paraguay basin, Brazil, revealed a population of Otothyropsis with uncertain taxonomic identity. Therefore, the study aimed to unveil the distribution of Otothyropsis within Brazilian territory. External morphology, osteology, measurements, and counts (plates, teeth, and rays) of these specimens from rio Tererê were compared to data from the original description of O. piribebuy, and also with specimens of O. piribebuy sampled in Paraguayan territory. Observations indicated no differences among the analyzed specimens. Furthermore, a Principal Component Analysis (PCA), carried out using log-transformed measures from Brazilian and Paraguayan specimens, showed no separation of these populations, also indicating that all analyzed specimens pertain to the same species. Based on this, a prediction map of distribution, using Maximum Entropy, was produced. The correct identification of spatial range of occurrence is an essential step to ensure the conservation of species, and the extended distribution of Otothyropsis piribebuy was confirmed, enhancing the list of neotropical fish from Brazil.

First record and extended distribution of Otothyropsis piribebuy (Loricariidae: Hypoptopomatinae) in Brazil

Cascudinhos are a group of small benthic fishes included in the Hypoptopomatinae subfamily, inhabiting small to moderate streams and rivers within the Neotropical region, from Venezuela to Northern Argentina. Until now, Otothyropsis piribebuy originally described from the rio Paraguay basin, in Paraguay, is the only species of the genus not recorded in Brazil. Recent samples in the rio Tererê, rio Paraguay basin, Brazil, revealed a population of Otothyropsis with uncertain taxonomic identity. Therefore, the study aimed to unveil the distribution of Otothyropsis within Brazilian territory. External morphology, osteology, measurements, and counts (plates, teeth, and rays) of these specimens from rio Tererê were compared to data from the original description of O. piribebuy, and also with specimens of O. piribebuy sampled in Paraguayan territory. Observations indicated no differences among the analyzed specimens. Furthermore, a Principal Component Analysis (PCA), carried out using log-transformed measures from Brazilian and Paraguayan specimens, showed no separation of these populations, also indicating that all analyzed specimens pertain to the same species. Based on this, a prediction map of distribution, using Maximum Entropy, was produced. The correct identification of spatial range of occurrence is an essential step to ensure the conservation of species, and the extended distribution of Otothyropsis piribebuy was confirmed, enhancing the list of neotropical fish from Brazil.(AU)

Rhinolekos, a new genus with three new species of Hypoptopomatinae (Siluriformes: Loricariidae) from upper rio Paraná

Rhinolekos, gênero novo, e três espécies novas, R. britskii, R. garavelloi e R. schaeferi, são descritas do rio Paranaíba, drenagem do alto rio Paraná, região central do Brasil. Rhinolekos pode ser diagnosticado pela seguinte combinação de caracteres: porção anterior do composto supraneural-primeiro proximal radial da nadadeira dorsal contatando o espinho neural da nona ou décima vértebra; presença da placa látero-nasal; ausência da placa rostral mediana; presença da fenda peitoral axilar apenas nos juvenis; superfície ventral da cintura peitoral exposta apenas lateralmente; arrector fossae parcialmente fechado, abertura relativamente grande, estendendo-se em direção à base da nadadeira peitoral; processo anterior pareado do composto supraneural-primeiro proximal radial da nadadeira dorsal ausente; série mediana de placas contínua até a origem da nadadeira caudal; opérculo da íris presente; pterótico-supracleitro quadrangular, não se estendendo posteriormente; ausência de cristas no supraoccipital, este não contribuindo com a formação da porção dorsal da cápsula da bexiga natatória; placa subopercular presente; margens dorsal e ventral do focinho portando odontódes de tamanho e forma equivalentes aos demais da cabeça; pedúnculo caudal aproximadamente circular em corte transversal; quarto infraorbital expandido ventralmente.(AU)

Rhinolekos, new genus, and three new species, R. britskii, R. garavelloi, and R. schaeferi, are described from rio Paranaíba, upper rio Paraná drainage, central Brazil. Rhinolekos can be diagnosed by the following combination of characters: anterior portion of the compound supraneural-first dorsal-fin proximal radial contacting the neural spine of the 9th or 10th vertebrae; presence of the lateronasal plate; absence of the median rostral plate; presence of the pectoral-fin axillary slit just in juvenile specimens; ventral surface of pectoral girdle exposed only laterally; arrector fossae partially enclosed, with opening relatively large, extending laterally halfway towards pectoral-fin base; paired anterior process of the compound supraneural-first dorsalfin proximal radial bone absent; median plate series continuous to the caudal-fin origin; iris operculum present; pteroticsupracleithrum quadrangular in shape and not extending posteriorly; supraoccipital not contributing to the dorsal portion of the swimbladder capsule; subopercular plate present; dorsal and ventral margins of snout bearing odontodes roughly equivalent in size and shape to those on remainder of the head; caudal peduncle roughly rounded in cross section; longitudinal crests in supraoccipital absent; fourth infraorbital expanded ventrally.(AU)

Microlepidogaster dimorpha, a new species of Hypoptopomatinae (Siluriformes: Loricariidae) from the upper rio Paraná system

Microlepidogaster dimorpha, espécie nova, é descrita de tributários do rio Grande, drenagem do alto rio Paraná. Microlepidogaster dimorpha difere de M. perforatus e M. longicolla por apresentar o primeiro radial proximal da nadadeira dorsal contactando o espinho neural da sétima vértebra, com sua porção posterior contactando também o oitavo centro vertebral (vs. primeiro radial proximal contactando o espinho neural da oitava ou nona vértebra em M. perforatus e o espinho neural da décima ou décima primeira vértebra em M. longicolla); 29-30 vértebras (vs. 31 em M. perforatus; e 31-33 em M. longicolla); 18-21 placas médio-dorsais (vs. 9-13 em M. perforatus, e 13-17 em M. longicolla); pedúnculo caudal alto (10,0- 11,4% no comprimento-padrão vs. 7,7-8,5% em M. perforatus e 5,4-7,3% em M. longicolla); distância entre a origem da nadadeira dorsal e a inserção da nadadeira anal 19,4-23,8% no comprimento-padrão (vs. 16,4-18,8% em M. perforatus e 14,7- 16,2% in M. longicolla); e narina nitidamente mais larga em machos do que em fêmeas (vs. aproximadamente equivalentes em tamanho em ambos os sexos, ligeiramente mais larga em machos em M. perforatus, e equivalentes em tamanho em ambos os sexos em M. longicolla). Microlepidogaster dimorpha também difere de M. perforatus pelo opérculo da íris presente (vs. ausente); série de placas mediana completa até o fim do pedúnculo caudal (vs. série de placas mediana truncada, as duas últimas placas das séries dorsal e ventral em contato); altura da cabeça 43,4-53,1% no comprimento da cabeça (vs. 40,7-42,3%); maior diâmetro orbital, 13,6-18,5% no comprimento da cabeça (vs. 11,1-13,5%); raio indiviso da nadadeira pélvica maior em machos do que nas fêmeas (vs. equivalente em ambos os sexos); e ausência de processos anteriores pareados no supraneural (vs. presença). Adicionalmente, M. dimorpha pode ser distinguido de M. longicolla por apresentar a margem anterior do focinho com uma placa rostral pareada (vs. focinho com pequenas placas, nu na margem anterior); fenda axilar da nadadeira peitoral presente, inclusive em espécimes adultos (vs. fenda axilar da nadadeira peitoral presente apenas em espécimes juvenis); raio indiviso da nadadeira peitoral longo (20,0-23,8% no comprimento-padrão vs. 13,4-16,2% em M. longicolla).(AU)

Microlepidogaster dimorpha, new species, is described from tributaries of rio Grande, upper rio Paraná system. Microlepidogaster dimorpha differs from M. perforatus and M. longicolla by having first dorsal-fin proximal radial attached to the neural spine of seventh vertebra, with posterior portion contacting also the eighth centrum (vs. first dorsal-fin proximal radial attached to the neural spine of eighth or ninth vertebra in M. perforatus, and to the neural spine of tenth or eleventh vertebra in M. longicolla); 29-30 vertebrae (vs. 31 in M. perforatus and 31-33 in M. longicolla); 18-21 mid-dorsal plates (vs. 9-13 in M. perforatus, and 13-17 in M. longicolla); deeper caudal peduncle (10.0-11.4% in SL vs. 7.7-8.5% in M. perforatus, and 5.4-7.3% in M. longicolla); greater distance between dorsal-fin origin and anal-fin insertion (19.4-23.8% in SL vs. 16.4-18.8% in M. perforatus, and 14.7-16.2% in M. longicolla); and nostril width markedly wider in males than in females (vs. approximately equivalent in size for both sexes, slightly wider in males than in females in M. perforatus, and equivalent in size for both sexes in M. longicolla). Microlepidogaster dimorpha also differs from M. perforatus by presence of the iris operculum (vs. absence); median plate series complete to caudal peduncle end (vs. median plate series truncated, with last two plates of dorsal and ventral series contacting in midline); greater head depth (43.4-53.1% vs. 40.7-42.3% in HL); greater orbital diameter (13.6-18.5% vs. 11.1-13.5% in HL); pelvic-fin first unbranched ray longer in males than in females (vs. equivalent in size in both sexes); and supraneural without paired anterior processes (vs. processes present). Additionally, M. dimorpha can be distinguished from M. longicolla by having anterior margin of snout with a paired rostral plate (vs. snout with small plates, naked in the anterior margin); by pectoral-fin axillary slit present, even in adult specimens (vs. pectoral-fin axillary slit present only in juvenile specimens); longer pectoral-fin unbranched ray (20.0-23.8% vs. 13.4-16.2% in SL in M. longicolla).(AU)