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

Abstract

The lepidophagous stegophiline catfish Ochmacanthus batrachostoma (Miranda-Ribeiro, 1912) is endemic to the Paraná-Paraguai basin and is the only member of its genus in that drainage. It remains a poorly-known taxon mainly due to the historical scarcity of study specimens. The species is herein redescribed on the basis of type and non-type specimens from Brazil, Argentina and Paraguay. Ochmacanthus batrachostoma can be distinguished from congeners by the presence of long maxillary and rictal barbels, reduction of the posterior end of the caudal peduncle, a tadpole-like caudal fin and peduncle, among other morphometric traits and features of internal anatomy. Comparisons show that a number of unique traits of adult O. batrachostoma resemble conditions seen in juvenile specimens of other members of Stegophilinae. Such traits are also more pronounced in juveniles of O. batrachostoma itself. The species also has the smallest maximum body size in Ochmacanthus and among the smallest of any stegophiline. In combination, such observations suggest that the species is paedomorphic, although to a degree less extreme than seen in some other trichomycterids. This is the first possible case of paedomorphosis identified for stegophilines.

Unrevealing Parasitic Trophic Interactions—A Molecular Approach for Fluid-Feeding Fishes

“…The vandeliines feed exclusively on blood from the gills of other fishes (Kelley and Atz, 1964;Machado and Sazima, 1983) while the stegophilines have been reported as scale and mucus-feeders (Eigenmann and Allen, 1942;Roberts, 1972;Baskin et al, 1980;Machado and Sazima, 1983;Winemiller and Yan, 1989;Neto and de Pinna, 2016). The feeding habits of the representatives of a third subfamily, the Tridentinae, remains uncertain, but there are circumstantial records of semiparasitic (scale-eating) or predation of small invertebrates among its species.…”

Ecological interaction of a “parasitic” candiru catfish and botos (Inia geoffrensis)

“…a). Ochmacanthus candirus are known for being mucophagous and are likely clinging to the botos with their sucker‐like apparatus and teeth (see Zuanon and Sazima , Neto and de Pinna ). Burst series of photographs and underwater video images showed that some candirus can move quite freely, quickly, and frequently around the body of the botos.…”

Ficha de Ochmacanthus batrachostoma

“…Distribuição Nacional Estados Mato Grosso, Mato Grosso do Sul Biomas Pantanal Bacias Hidrográficas Sub-bacia Paraguai 01, Sub-bacia Paraguai 02, Sub-bacia Paraguai 03 (Neto & de Pinna, 2016).…”

“…Endêmica do Brasil: Não Ochmacanthus batrachostoma é conhecida das bacias dos rios Paraguai e Paraná, na na Bolívia (Sarmiento et al, 2014), Brasil, Paraguai e na Argentina (Neto & de Pinna, 2016).…”