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| Rhyacoglanis varii Shibatta & Souza-Shibatta. 2023. |
Abstract
A new species of Rhyacoglanis from the upper rio Tocantins basin is described based on morphological and molecular data. The new species differs from the congeners by its color pattern, caudal fin shape, hypural bones fusion pattern, pectoral-fin spine shape, and barcode sequence of cytochrome oxidase subunit I (COI). In this study, two putative monophyletic groups of Rhyacoglanis are proposed based on morphology, one consisting of species with a short post-cleithral process and caudal fin with rounded lobes, Rhyacoglanis epiblepsis and R. rapppy-danielae, and the other with a longer post-cleithral process and caudal fin with pointed lobes, R. annulatus, R. paranensis, R. pulcher, R. seminiger, and the new species described herein.
Keywords: Biodiversity; Bumblebee catfish; Ostariophysi; Systematics; Taxonomy
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| Holotype of Rhyacoglanis varii, MZUEL 22317, 67.1 mm SL, rio do Peixe, upper rio Tocantins basin, Goianésia, state of Goiás, Brazil. |
Rhyacoglanis varii, new species
Diagnosis: Rhyacoglanis varii is easily distinguished from congeners (except for R. pulcher) by the color pattern, with the dark brown vertical bar below the dorsal-fin base not confluent with a dark brown bar below the adipose-fin base (vs. broadly confluent in R. seminiger), the subdorsal dark brown bar becomes abruptly thinner ventrally (vs. broader in R. paranensis), dark brown spots sparsely distributed on the body (vs. dense in R. epiblepsis and R. rapppydanielae), and a solid dark brown bar on caudal peduncle (vs. becoming light brown inside, resembling a circle, in R. annulatus). Rhyacoglanis varii has the posterior tip of the post-cleithral process reaching vertical through the base of the dorsal-fin spine (vs. not reaching in R. epiblepsis and R. rappydanielae). Rhyacoglanis varii differs from R. paranensis by the longer distance of anus to anal-fin origin (mean = 11.4±0.8% vs. 10.0±1.4% SL), maxillary barbel length (mean = 79.6±5.8% vs. 74.8±8.7% SL), and caudal peduncle depth (mean = 9.5±0.5% vs. 8.8±0.5% SL); minor posterior nostril to eye distance (mean = 4.8±0.9% vs. 6.7±1.3% SL), body depth (mean = 18.2±1.5% vs. 21.4±2.6% SL), and postcleithral process length (mean = 12.9±1.1% vs. 13.9±1.2% SL). Rhyacoglanis varii differs from R. pulcher and R. seminiger by the shape of the pectoral-fin spine, with anterior serrae distributed along the entire margin (vs. restricted to the proximal half).
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| Rhyacoglanis varii coloration in life, MZUEL 6039, paratype, 46.1 mm SL, rio do Peixe, upper rio Tocantins basin, Goianésia, state of Goiás, Brazil. |
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| A. Panoramic view of Rhyacoglanis varii type locality, rio do Peixe, Goianésia, state of Goiás, Brazil; B. Bottom with rocks, pebbles, and sand where specimens were collected; C. Blue arrow indicating water flow and pointing to a specimen beneath rocks. |
Etymology. The species name varii honors the ichthyologist Richard P. Vari (1949–2016) for his outstanding contributions to the systematics of Neotropical fishes.
Oscar Akio Shibatta and Lenice Souza-Shibatta. 2023. New species of Rhyacoglanis (Siluriformes: Pseudopimelodidae) from the upper rio Tocantins Basin. Neotrop. ichthyol. 21(1); DOI: 10.1590/1982-0224-2022-0075
Resumo: Uma nova espécie de Rhyacoglanis da bacia do alto rio Tocantins é descrita com base em dados morfológicos e moleculares. A nova espécie difere das congêneres por seu padrão de colorido, forma da nadadeira caudal, padrão de fusão dos ossos hipurais, forma do espinho da nadadeira peitoral e sequência de código de barras do citocromo oxidase subunidade I (COI). Neste estudo, dois possíveis grupos monofiléticos de Rhyacoglanis são propostos com base na morfologia, constituídos por espécies com o processo pós-cleithral curto e nadadeira caudal com lóbulos arredondados, Rhyacoglanis epiblepsis e R. rapppydanielae, e o outro com o processo pós-cleithral mais alongado e nadadeira caudal com lóbulos pontiagudos, R. annulatus, R. paranensis, R. pulcher, R. seminiger, e a nova espécie aqui descrita.
Palavras-chave: Bagrinho; Biodiversidade; Ostariophysi; Sistemática; Taxonomia