A New Species of Silverside of the Genus Odontesthes (Atheriniformes: Atherinopsidae) with Hypertrophic Lips from a High-Altitude Basin in Southern Brazil
Odontesthes crossognathos, new species, is described from the Pelotas River basin, upper Uruguay River, southern Brazil. The new species is easily diagnosed by the possession of hypertrophied lips bearing numerous dermal papillae, a character absent in other species of the genus. The new species is also distinguished from congeners, except O. humensis, by having the upper jaw distinctly longer than the lower jaw and a subterminal mouth. These mouth morphology adaptations are probably related to the foraging behavior of the new species, which inhabits rivers with rapids and rocky bottoms in a high-altitude basin.
Odontesthes crossognathos, espécie nova, é descrita da bacia do rio Pelotas, alto rio Uruguai, sul do Brasil. A nova espécie é facilmente diagnosticável por possuir lábios hipertrofiados com numerosas papilas dérmicas, caráter ausente em outras espécies do gênero. A nova espécie também se distingue das congêneres, exceto de O. humensis, por ter a mandíbula superior distintamente mais longa do que a inferior e a boca subterminal. Essas adaptações na morfologia da boca provavelmente estão relacionadas ao comportamento de forrageamento da nova espécie, que habita rios de corredeiras e fundos rochosos em uma bacia de altitude elevada.
Odontesthes crossognathos, in lateral view. (A) Holotype, UFRGS 27180, 183.7 mm SL, Invernadinha Stream, tributary to the Pelotas River in the locality of Luisinho, upper Uruguay River basin, municipality of São Joaquim, Santa Catarina State, Brazil; (B) paratype, UFRGS 28745, 103.2 mm SL, collected with the holotype.
Snout of Odontesthes crossognathos, in lateral view, anterior to left, paratype, UFRGS 28830, CS, 134.6 mm SL. Arrows indicate the dermal papillae. Scale bar = 2 mm.
Head of Odontesthes crossognathos, in lateral view. (A) Holotype, UFRGS 27180, 183.7 mm SL; (B) paratype, UFRGS 28745, 103.2 mm SL. Arrow indicates the dermal papillae.
Opercle in dorsal view. (A) Odontesthes crossognathos, left side, anterior to left, paratype, UFRGS 28830, 134.6 mm SL; (B) Odontesthes humensis, left side, anterior to left, UFRGS 4130, 134 mm SL. Arrows indicate the ventral border. Scale bar = 2 mm.
Pectoral girdle in dorsal view. (Left) Odontesthes humensis, left side, anterior to left, UFRGS 22497, 130.3 mm SL; (Right) Odontesthes crossognathos, right side, anterior to left, paratype, UFRGS 28830, 134.6 mm SL. Arrows indicate the dorsomedial wing surpassing the suture between scapula (S) and coracoid (C). Scale bar = 2 mm.
Pelvic girdle in dorsal view. (Left) Odontesthes humensis, right side, anterior to left, UFRGS 22497, 130.3 mm SL; (Right) Odontesthes crossognathos, left side, anterior to left, paratype, UFRGS 28830, 134.6 mm SL. Black arrows indicate the angle of dorsolateral process (dp) with dorsal plate (dpl). Gray arrows indicate the shape and direction of the median process (mp). Scale bar = 2 mm.
Histological section of the lip of Odontesthes crossognathos showing dermal papillae (black arrows) as fingerlike projections from dermis constituted by loose connective tissue (lct), and projected through epidermal layers of pavement cells and reaching stratified squamous epithelial tissue (sste). EP = epidermis; DE = dermis; (*) = technique artifact. Scale bar = 200 μm.
Distribution of Odontesthes crossognathos in the Pelotas River basin, Upper Uruguay River drainage, Rio Grande do Sul and Santa Catarina states, south Brazil. Star represents the type locality.
Haplotype network illustrating the genetic connectivity of COI haplotypes of Odontesthes crossognathos and congeners. Each circle represents a unique haplotype with circle sizes being proportional to their frequencies. Each color represents a different species of Odontesthes. Crossed markers in the branches that connect the haplotypes represent the number of mutations.
Contributor Notes
Associate Editor: R. E. Reis.