A New Species of the Banjo Catfish Genus Ernstichthys (Siluriformes: Aspredinidae) from the Bermejo River Drainage, La Plata Basin, Argentina
The upper Bermejo River basin houses a great diversity of fishes, represented by the endemic species, the shared fauna between the Paraguay and the Amazon basins, and the elements from the Paraná River basin. During recent surveys in the area, many specimens of an undescribed Ernstichthys were collected in four different localities of northwestern Argentina and are herein described as a new species. The new species, Ernstichthys casalinuovoi, is distinguished from the remaining species of the genus by a combination of characters including the number of lateral plates on the body, the shape of the second pre-anal-fin plate, the presence of a rictal barbel, the coloration pattern, the number of total vertebrae, the unbranched maxillary barbel, and the number of serrations on the posterior margin of the pectoral-fin spine, among others. The large batch used to describe Ernstichthys casalinuovoi, new species, has allowed us to detect characters that should be treated carefully in the description of species belonging to Ernstichthys such as the number of serrations on the posterior margin of the pectoral-fin spine or the overlap between bony elements on the caudal peduncle given that they could vary according to ontogeny. The new species herein described represents the fifth species of the genus and the first record of Ernstichthys and the Hoplomyzontinae in Argentina.
Ernstichthys casalinuovoi, holotype, male, CI-FML 8098, 34.3 mm SL. Dorsal, lateral, and ventral views. Scale bar 1 cm.
Ernstichthys casalinuovoi, holotype, CI-FML 8098, 34.3 mm SL, live specimen before fixation.
Pre-anal-fin plates of (A) Ernstichthys casalinuovoi, (B) E. anduzei, (C) E. megistus, (D) E. intonsus, and (E) E. taquari. Drawings B to D adapted from Stewart (1985) and E drawn from the CT scan by Dagosta and de Pinna (2021).
Rictal papillae of Ernstichthys casalinuovoi, holotype, CI-FML 8098.
Dorsal plates on caudal peduncle. Above, dorsal plates in contact with each other in a larger specimen (CI-FML 8104, 29.8 mm SL); below, dorsal plates separated from each other in a smaller specimen (CI-FML 8100, 22.6 mm SL). Scale bar 2 mm.
Schematic representation of skull in adult Ernstichthys casalinuovoi. Abbreviations: cv, complex vertebra; fr, frontals; io1, first infraorbital; mes, mesethmoid; mx, maxilla; pso, parietosupraoccipital; pto, pterotic; pv5, parapophysis of fifth vertebra; sc, posttemporosupracleithrum; spo, sphenotic.
Color variation of Ernstichthys casalinuovoi in dorsal view. CFA-IC 12923 (A: live specimen and C: preserved specimen); CI-FML 8099 (B: live specimen and D: preserved specimen); CI-FML 8103 (E–F: live specimen and G–H: preserved specimens). Scale bar 1 cm.
Distribution of Ernstichthys casalinuovoi. Red star indicates the holotype. (A) San Lorenzo River (23°49′45.5″S, 64°39′05.5″W), Jujuy Province, where the holotype was collected; (B) microhabitat were the holotype was found; (C) Lavayén River (24°02′43.7″S, 64°42′00.6″W).
Phylogenetic relationships of hoplomyzontine species obtained from CO1 data in a Bayesian analysis. Species names followed by GenBank accession number of the sequence used. See Data Accessibility for tree file.
Linear regression analysis between the standard length and the number of serrae on posterior margin of pectoral-fin spine, including all species of Ernstichthys. The equation and coefficient of determination R2 are provided in the image.
Contributor Notes
Associate Editor: R. E. Reis
These authors contributed equally.