A new species of the catfish genus Trichomycterus ( Teleostei : Siluriformes : Trichomycteridae ) from the Paranaíba basin , Central Brazil

Trichomycterus giarettai, new species, from a small river in Cumari municipality, Central Brazil is described. It is hypothesized to be closely related to species of T. brasiliensis complex by possessing the opercular odontodes disposed obliquely on the patch. Trichomycterus giarettai is diagnosed by the distribution of infraorbital pores, body width, caudal peduncle width, number of vertebrae, branchiostegal rays, dorsal and ventral procurrent rays, opercular and interopercular odontodes, length of the nasal barbels, and pelvic fin insertion.


Trichomycterus giarettai new species
Description.Morphometric data for holotype and paratypes given in Table 1.Body moderately deep, subcylindrical on anterior portion, compressed on caudal peduncle.Dorsal profile slightly convex between snout and end of dorsal-fin base, straight on caudal peduncle.Ventral profile straight to slightly convex between lower jaw and end of anal-fin base, straight on caudal peduncle.Greatest body depth in vertical immediately in front of pelvic-fin origin.Skin papillae minute.Urogenital papilla conical, in vertical through anterior third of dorsal-fin base.Dorsal and anal fins approximately triangular.Dorsalfin origin in vertical through centrum of 20 th vertebra.Anal-fin origin in vertical just posterior to midlength of dorsal-fin base and through centrum of 23 th vertebra.Pectoral fin about triangular, lateral and posterior edges slightly convex.First pectoral-fin ray terminating in short filament, about 15% of pectoral-fin length.Pelvic fin shorter than anal fin, covering urogenital opening, tip not reaching anal fin, in vertical just anterior to dorsal-fin origin; pelvic girdle short with mesial process absent or vestigial; pelvic-fin bases medially in close proximity; pelvic-fin inserction through vertical centrum of 17th or 19th vertebra.Caudal fin subtruncated, posterior margin slightly convex.Dorsal-fin rays 11; anal-fin rays 9 -10; pectoral-fin rays 7; pelvic-fin rays 5; caudal-fin principal rays 13, dorsal procurrent rays 20 -21, ventral procurrent rays 17 -18.Total vertebrae 35 -36; pleural ribs 13 -15.Upper hypural plates separated, dorsal plate much wider than ventral plate, or ventral and dorsal plate with approximately the same width.
Supraorbital canal with three pores; first pore in transverse line through anterior nostril, second in transverse line just posterior to posterior nostril, third in transverse line just posterior to orbit; third pore approximately equidistant to symmetrical pore and orbit.Infraorbital canal restricted to two pores; first and second pores absent; third and fourth present and posterior to orbit.Preopercular canal with one pore, in vertical through anterior margin of opercular patch of odontodes.Lateral line of body short, with three pores, posteriormost pore in vertical just posterior to pectoral-fin base.

Colouration in alcohol.
Side of body and head pale yellowish brown, with dark brown dots coalesced to form reticulate pattern; venter yellowish; barbels brown.Fins hyaline with brown bases; pectoral-fin filament white.In juveniles, narrow dark brown stripe along lateral midline; dorsal dark brown with dark brown dots coalesced to form vermiculate or reticulate pattern; flank brown   with dark brown dots above, and light yellowish with small dark brown spots below midline.
Distribution.Known only from a small stream, tributary of the upper rio Paranaíba basin, Central Brazil.
Etymology.The name "giarettai" was given in honor to the herpetologist A. Giaretta, that first collected the new species in the field.
Discussion.The Paranaíba river basin, where the new species was found, is the second largest forming unit of the Paraná river basin, occupying 25.4% of its area, located in central Brazil.The tributaries of this wide basin drains part of Brazilian Shield and, despite being part of the upper Rio Paraná basin, seems to include a slightly different fauna (Costa, 1996;Costa, 2011;PaVanelli & BritsKi, 1999).
BarBosa & Costa (2010a) recognized the T. brasilien sis complex based on the presence of a unique arrangement of opercular odontodes, disposed obliquely.This group consists of fourteen species distributed through the upper São Francisco, Paraíba do Sul, and Paraná river basins, as well as, small coastal river basins in southeastern Brazil (BarBosa & Costa, 2012a,b;2013).Trichomycterus gia rettai, the first species of the genus described for Central Brazil, also possesses the unique arrangement of opercular odontodes, disposed obliquely, therefore being here hypothesized as belonging to the T. brasiliensis species complex.It differs from all other species of T. brasilien sis complex by the distribution of infraorbital pores, body width, caudal peduncle width, number of vertebrae, branchiostegal rays, dorsal and ventral procurrent rays, opercular and interopercular odontodes, length of the nasal barbels, and pelvic fin insertion.Species of T. brasiliensis complex are very similar to each other, with all of them showing colour pattern possessing dark brown dots coalesced to form reticulate pattern.Because of this external similarity they were historically poorly identified and almost indistinguishable externally (BarBosa & Costa, 2010).Therefore, detailed morphology studies have shown that many of these seemingly similar species have many morphological informative features for taxonomy, allowing robust diagnosis of new species and being an important tool to recognize species (Costa, 1992;BarBosa & Costa, 2003;BarBosa & Costa, 2010a, b;Katz et al., 2013).The number of species is probably much greater than the current biodiversity estimates (e.g.BiCKFord et al., 2006).