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

Abstract

A new species of the candiru genus Paracanthopoma is described from the floodplains of the Bananal Island, a transition area between the Cerrado and Amazon, in the Araguaia River basin, central Brazil. Paracanthopoma cangussu sp. nov. is distinguished from its congeners, Paracanthopoma parva and Paracanthopoma saci, by the presence of seven opercular odontodes, five dentary teeth, five median premaxillary teeth, and first dorsal-fin pterygiophore in a vertical through the centrum of the 23th or 24th vertebra. It is further distinguished from each congener by an exclusive combination of character states, comprising the number of vertebrae, number of precaudal vertebrae, number of dorsal procurrent caudal-fin rays, number of ventral procurrent caudal-fin rays, number of dorsal-fin rays, disposition of pores on the cephalic portion of the latero-sensory system, absence of an anterior process on the anterior margin of parieto-supraoccipital, number of dorsal-fin pteryigiophores and number of interopercular odontodes. Although vandelliines are known for being exclusively hematophagous, with guts gorged with blood, two cleared and stained specimens of P. cangussu sp. nov. had Chironomidae larvae (Insecta) on their guts. Because most specimens of P. cangussu sp. nov. were collected with stomachs filled with blood, it was hypothesized that the species feeds accidentally or occasionally on insects.

Two new miniature translucent catfish species of the rare genus Tridens (Siluriformes: Trichomycteridae) from the Madeira River basin, northern Brazil

“…Tridens vitreus and T. chicomendesi are markedly distinct from each other on their cranial anatomy, with the maxilla being the most striking difference in their skulls. Whereas in T. vitreus the maxilla is entirely cartilaginous, robust and long (Figure 3a), in T. chicomendesi it is completely ossified and thin (Figure 3b), as seen in some other members of the TSV‐clade ( i.e ., the clade composed by Tridentinae, Stegophilinae and Vandelliinae; e.g ., Henschel et al ., 2021, Figures 2 and 8; DoNascimiento, 2015, Figure 3b). A cartilaginous maxilla is not seen in any other adult individuals of Trichomycteridae, but further examination of this condition in other tridentines is needed to confirm it as exclusive at the family level for T. vitreus .…”

“…These labial teeth can be seen in the two species herein described (Figure 9) and occur independently in other trichomycterids, such as Tridensimilis venezuelae (Schultz, 1944), and in some stegophilines (DoNascimiento, 2015). The presence of a free gill membrane across the isthmus is confirmed in both species and is also seen in Tridensimilis (Schultz, 1944), Tridentopsis (Azpelicueta, 1990; Myers, 1925) and other members of Trichomycteridae ( e.g ., Dagosta & de Pinna, 2021; Henschel et al ., 2021; Myers & Weitzman, 1966; de Pinna & Dagosta, 2022). The maxillary and rictal barbels are poorly developed in some tridentines, which led Baskin (1973) to consider that the latter are not externally visible in species of Tridens, Tridensimilis and Tridentopsis and Eigenmann (1918, Plate XLIII, Figures 1 and 2) to represent a paratype of T. melanops without rictal barbels, as opposed to his text and to the original description of T. melanops published earlier by himself (Eigenmann & Eigenmann, 1889).…”

“…The recently described subfamily Microcambevinae comprises interstitial species that spend most of their lives buried in sandy substrates in river basins of the Atlantic Forest of eastern, south‐eastern and southern Brazil allocated in the genus Microcambeva (Costa & Bockmann, 1994), whereas species of Listrura de Pinna, 1992 mostly inhabit leaf litter−covered bottom substrates (Costa, Henschel et al ., 2020; Costa & Katz, 2021a; Villa‐Verde et al ., 2022). On the contrary, Tridentinae, Stegophilinae, Vandelliinae, Sarcoglanidinae and Glanapteryginae (known as the TSVSG‐clade; Costa & Bockmann, 1994) are mostly found in the Amazon River basin, with a few representatives in the Pantanal ( e.g ., Miranda‐Ribeiro, 1912), Chaco (Azpelicueta, 1990), Atlantic Forest ( e.g ., Miranda‐Ribeiro, 1944, Koch, 2002), Caatinga ( e.g ., Costa et al ., 2019) and Cerrado ( e.g ., Henschel et al ., 2021; Reinhardt, 1859). Whereas information on the habits of tridentines is scarce, vandelliines and stegophilines are found usually associated with sandbanks, roots of aquatic plants ( e.g ., Miranda‐Ribeiro, 1912; Henschel et al ., 2021; E.H. and W.J.E.M.C., pers.…”

“…On the contrary, Tridentinae, Stegophilinae, Vandelliinae, Sarcoglanidinae and Glanapteryginae (known as the TSVSG‐clade; Costa & Bockmann, 1994) are mostly found in the Amazon River basin, with a few representatives in the Pantanal ( e.g ., Miranda‐Ribeiro, 1912), Chaco (Azpelicueta, 1990), Atlantic Forest ( e.g ., Miranda‐Ribeiro, 1944, Koch, 2002), Caatinga ( e.g ., Costa et al ., 2019) and Cerrado ( e.g ., Henschel et al ., 2021; Reinhardt, 1859). Whereas information on the habits of tridentines is scarce, vandelliines and stegophilines are found usually associated with sandbanks, roots of aquatic plants ( e.g ., Miranda‐Ribeiro, 1912; Henschel et al ., 2021; E.H. and W.J.E.M.C., pers. obs.)…”

“…The rich natural histories underlying the striking diversity of these subfamilies led to a significant increase in the number of taxonomic works concerning the family, revealed by the description of 123 species of trichomycterids in the last 10 years (Fricke et al ., 2022). Nonetheless, these data hide an important collection and publication bias that affects studies focused on Trichomyteridae: most concern the diversity of trichomycterines from southern and southeastern Brazil ( e.g ., Costa et al ., 2022; Costa, Henschel et al ., 2020; Costa & Katz, 2021b; Reis et al ., 2022), with fewer efforts directed to members of the TSVSG‐clade, such as vandelliines (Dagosta & de Pinna, 2021; Henschel et al ., 2021; Henschel et al ., 2022; de Pinna & Dagosta, 2022) and sarcoglanidines (Costa et al ., 2019; Henschel, Bragança et al ., 2020; Henschel, Lujan et al, 2020; Canto et al ., 2022).…”