Abstract
Two species of Cosmetocleithrum Kritsky, Thatcher & Boeger, 1986 (both new) and two species of Demidospermus Suriano, 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 berecae n. 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 nunani n. 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 tocantinensis n. sp. is easily distinguished from other species of the genus by presenting an inverted-G-shaped MCO with a median knee-like expansion. Demidospermus osteomystax Tavernari, Takemoto, Lacerda & Pavanelli, 2010 is redescribed based on paratypes and specimens from the gills of A. nuchalis from the Tocantins River, a new host and locality records for this species. The monotypic Paracosmetocleithrum Acosta, Scholz, Blasco-Costa, Alves & Silva, 2017, the only other Neotropical genus reported in siluriforms besides Cosmetocleithrum with species presenting two ribbon-like projections on the posterior margin of the dorsal bar, is considered a junior subjective synonym of Cosmetocleithrum.
Highlights
Siluriformes is a large and diverse order of fishes, collectively known as catfishes
Siluriforms are hosts to an extraordinarily rich and diverse fauna of gill monogenoids, and this host-parasite system represents an attractive model for phylogenetic studies in the Neotropical Region [27]
The global fauna of the Dactylogyridae infecting catfishes is very diverse and includes around 379 species belonging to 31 genera [25]
Summary
Siluriformes is a large and diverse order of fishes, collectively known as catfishes. Most of them are omnivores, unlike most freshwater fishes, nocturnal, and depend mainly on senses other than sight, such as tactile and chemo-sensitive barbels to explore their surroundings [20]. Siluriforms are hosts to an extraordinarily rich and diverse fauna of gill monogenoids, and this host-parasite system represents an attractive model for phylogenetic studies in the Neotropical Region [27]. The global fauna of the Dactylogyridae infecting catfishes is very diverse and includes around 379 species belonging to 31 genera [25]. Almost half of the genera (14) and about 75 species are native to the Neotropical Region [25]. Demidospermus Suriano, 1983 and Cosmetocleithrum Kritsky, Thatcher & Boeger, 1986 are the most diverse genera among dactylogyrids of Neotropical catfishes
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