Two new catfish species of typically Amazonian lineages in the Upper Rio Paraguay (Aspredinidae: Hoplomyzontinae and Trichomycteridae: Vandelliinae), with a biogeographic discussion

Abstract

Two new species of particular biogeographic significance are described from the upper rio Paraguay basin, one of the genus Paracanthopoma (Trichomycteridae, Vandelliinae) and the other of the genus Ernstichthys (Aspredinidae, Hoplomyzontinae). The two species occur sympatrically in the Rio Taquarizinho, tributary of the Rio Taquari, in the upper Paraguay system. Paracanthopoma saci is distinguished from its only congener, P. parva, by a spatulate caudal peduncle; a minuscule premaxillary dentition (reduced to three delicate teeth); the supraorbital latero-sensory canals opening as two separate s6 pores; the caudal fin slightly convex or truncate with round edges; the skull roof entirely open, unossified; the origins of dorsal and anal fins approximately at same vertical; and the pelvic fin with three rays. Ernstichthys taquari is diagnosed among congeners by the narrow bony shields on dorsal and ventral series, not overlapping or contacting each other; by the presence of seven or eight serrations on the posterior margin of the pectoral spine; and by the pectoral-fin spine only slightly larger than subsequent soft rays. Both Paracanthopoma and Ernstichthys were previously unknown outside of the Greater Amazonian river systems (Amazon, Orinoco, Essequibo and smaller surrounding drainages). Their presence restricted to the Rio Taquari is unexpected and suggests a peculiar biogeographical history. Ancestral geographic distributions were reconstructed using S-DIVA and BBM methods in RASP. A majority of resulting hypotheses support that the two species reached the Paraguay from the Amazon. The alternative explanation accounts for their presence in the Paraguay by vicariant events. In no case, their presence in the Paraguay is an ancestral distribution with subsequent Amazonian dispersal. Though unusual, this pattern is also seen in a few other fish taxa, showing that the Rio Taquari is biogeographically hybrid, combining elements from both the Paraguay and Amazon drainages.

The Genetic Differentiation of Pyrrhulina (Teleostei, Characiformes) Species is Likely Influenced by Both Geographical Distribution and Chromosomal Rearrangements

“…They are also distinct morphologically ( Netto-Ferreira and Marinho, 2013 ) and present non-overlapping distributions in the Amazon basin. Pyrrhulina semifasciata occur in the Purus, Juruá, Negro, Branco rivers, Amazonas main channel ( Dagosta and De Pinna, 2021 ), and Madeira River while P. marilynae is restricted to the upper portions of Tapajós and Xingu ( Netto-Ferreira & Marinho, 2013 ) ( Figure 1 ). Similarly, values of Dxy and Da between P. semifasciata and P. australis are also very high (0.0171 and 0.0144), indicating their genetic distinctiveness.…”

“…48628-14) and Sistema Nacional de Gestão do Patrimônio Genético e do Conhecimento Tradicional Associado (SISGEN - A96FF09). The distribution data was obtained from the analysis of scientific collection materials and previous literature ( Bertaco et al, 2016 ; Dagosta e Depinna 2021 ).…”

A new candiru of the genus Paracanthopoma (Siluriformes: Trichomycteridae) from the Araguaia River basin, central Brazil

“…Among the characters considered byGiltay (1935) as diagnostic for this species, a special emphasis was given to the presence of a free branchial membrane across the isthmus. This character state, considered a unique condition among vandellines(Schmidt, 1993;Dagosta and de Pinna, 2021), is found in P. cangussu (Figure1). Fifty-eight years later,Schmidt (1993) provided the first definition of Paracanthopoma within a…”

“…The genus Paracanthopoma represents one of the major taxonomic challenges among trichomycterids: the lack of osteological information on its type species (Paracanthopoma parva Giltay, 1935); and a myriad of undescribed species (DoNascimiento, 2012;Dagosta and de Pinna, 2021;E.H., pers. obs.…”

A taxonomic review of the vampire catfish genus Paracanthopoma Giltay, 1935 (Siluriformes, Trichomycteridae), with descriptions of nine new species and a revised diagnosis of the genus

“…After almost 90 years without taxonomic novelties, two new species of Paracanthopoma were reported in 2021: Pc. saci de Pinna, 2021 andPc. cangussu Henschel, Katz &Costa, 2021a.…”