| Abstrakt: |
Two species of CosmetocleithrumKritsky, Thatcher & Boeger, 1986 (both new) and two species of DemidospermusSuriano, 1983 (one new) are reported from the gills of the catfish Auchenipterus nuchalis,popularly known as “mapará”, from the Tocantins River and tributaries, North Region of Brazil. Cosmetocleithrum berecaen. sp. differs from all other species presently known in the genus by the morphology of the anchors presenting an elongate shaft and short recurved point, a coiled male copulatory organ (MCO) with three rings, and an elongate slender accessory piece with a bifurcated distal end. Cosmetocleithrum nunanin. sp. differs from its congeners by the combination of the following features: (1) Ventral and dorsal anchors with moderately long curved shaft and short point; (2) Hooks with poorly developed thumb; (3) Hook pairs 5 and 6 similar to each other, but morphologically distinct from remaining hook pairs; and (4) MCO coiled, with approximately 1.5 rings. Demidospermus tocantinensisn. sp. is easily distinguished from other species of the genus by presenting an inverted-G-shaped MCO with a median knee-like expansion. Demidospermus osteomystaxTavernari, Takemoto, Lacerda & Pavanelli, 2010 is redescribed based on paratypes and specimens from the gills of A. nuchalisfrom the Tocantins River, a new host and locality records for this species. The monotypic ParacosmetocleithrumAcosta, Scholz, Blasco-Costa, Alves & Silva, 2017, the only other Neotropical genus reported in siluriforms besides Cosmetocleithrumwith species presenting two ribbon-like projections on the posterior margin of the dorsal bar, is considered a junior subjective synonym of Cosmetocleithrum. |
