Ochmacanthus batrachostomus

conservation

Conservation status. Not present in any national or international lists of threatened species. According to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2014), Ochmacanthus batrachostoma can be classified as Least Concern (LC).

Redescription of Ochmacanthus batrachostoma (Miranda-Ribeiro, 1912) (Siluriformes: Trichomycteridae): a possible case of incipient paedomorphism

description

Description. Morphometric data are presented in Table 1. Body relatively elongate, depressed in cross section close to head and gradually more compressed towards tail. Dorsal body profile nearly straight on head, gently convex until end of dorsal fin and straight on caudal region, exclusive of accessory caudal rays. Ventral body profile gently convex until origin of anal fin and straight along caudal region, exclusive of accessory caudal rays. Body deepest at origin of dorsal fin. Dorsal and ventral profiles of caudal peduncle extremely expanded on proximal half, due to presence of well-developed procurrent caudal-fin rays and gradually less deep on distal half. Caudal peduncle profile exclusive of procurrent rays conical, with extremely fine tip, its depth approximately one fifth that at base. Head profile not perfectly continuous with trunk due to presence of opercular patch of odontodes. Myotomes visible along almost whole body, most prominently along posterior portion of trunk. Head broad and semicircular in dorsal view, depressed in lateral view. Length nearly equal to width. Snout short and rounded anteriorly. Mouth inferior, as broad as head, its corners directed posteriorly

Redescription of Ochmacanthus batrachostoma (Miranda-Ribeiro, 1912) (Siluriformes: Trichomycteridae): a possible case of incipient paedomorphism

diagnosis

Diagnosis. Ochmacanthus batrachostoma is easily distinguished from remaining species of its genus by any of the following characters: presence of long maxillary and rictal barbels (vs. short barbels), the former reaching the base of the pectoral fin and the latter more than half that length (vs. maxillary barbel not reaching beyond the interopercular patch of odontodes and rictal barbel not longer than the associated labial fold); the caudal peduncle expanded into a paddle-like shape by numerous large procurrent rays, with markedly convex dorsal and ventral profiles (vs. caudal peduncle approximately rectangular in shape, with straight or gently convex dorsal and ventral profiles); the muscular portion of the caudal peduncle tapering markedly posteriorly (vs. tapering gently to caudal fin), so that its posterior depth is 20 - 25 % of its anterior depth (vs. more than 25 %); the caudal fin shorter than 10 % of SL (vs. longer than 10 % of SL).

Redescription of Ochmacanthus batrachostoma (Miranda-Ribeiro, 1912) (Siluriformes: Trichomycteridae): a possible case of incipient paedomorphism

distribution

Distribution. Endemic to, and widely distributed in, the Paraná-Paraguai drainage, in Argentina, Brazil and Paraguay. Absent from the Upper Paraná and from the Prata drainage (Fig. 3).

Redescription of Ochmacanthus batrachostoma (Miranda-Ribeiro, 1912) (Siluriformes: Trichomycteridae): a possible case of incipient paedomorphism