Nanayella gen. n. is proposed to accommodate four new species of dactylogyrid monogeneans found on the gills of two species of pimelodid catfishes (Siluriformes) from the Amazon River basin in Peru and the Upper Paraná River basin in Brazil. Nanayella gen. n. is mainly characterised by the presence of modified hook pairs 5 and 6, which have a slender shank with slightly enlarged base, inconspicuous thumb, and straight point. Nanayella aculeatrium gen. n. et sp. n. (type species) from Sorubim lima (Bloch et Schneider) (type host) differs from its congeners mainly by possessing seven sclerotised spines on one side of circular ornamentation of the vaginal atrium. Nanayella fluctuatrium gen. n. et sp. n. is characterised by the presence of sclerotised undulations surrounding the circular ornamentation of the vaginal atrium. Nanayella amplofalcis gen. n. et sp. n. is typified by possessing hook pairs 1 and 2 with a robust, wide shank and a round, weakly sclerotised subunit at the base. Nanayella processusclavis gen. n. et sp. n. differs from congeners by the presence of a conspicuous posterior medial process on the dorsal bar. Urocleidoides megorchis Mizelle et Kritsky, 1969 described from the gills of S. lima in Brazil is transferred to Nanayella gen. n. as Nanayella megorchis comb. n. based on morphological and molecular evidence. Analyses of partial sequences of the 28S rRNA gene revealed all five species of the new genus to form a monophyletic clade within a bigger clade comprised of dactylogyrids of South American pimelodids., Aline A. Acosta, Carlos A. Mendoza-Palmero, Reinaldo J. da Silva, Tomáš Scholz., and Obsahuje bibliografii
During a survey of the parasites of freshwater fishes from cenotes (sinkholes) of the Yucatan Peninsula the following species of monogeneans were found on cichlid, pimelodid, characid and poeciliid fishes: Sciadicleithrum mexicanum Kritsky, Vidal-Martinez et Rodriguez-Canul, 1994 from C.ichlasoma urophthalmus (Giinther) (type host), Cichlasoma friedrichsthali (Heckel), Cichlasoma octofasciatum (Regan), and Cichlasoma synspilum Hubbs, all new host records; Sciadicleithrum meekii Mcndoza-Franco, Scholz et Vidal-Martinez, 1997 from Cichlasoma meeki (Brind); Urocleidoides chavarriai (Price, 1938) and Urocleidoides travassosi (Price, 1938) from Rhamdia guatemalensis (Günther); Urocleidoides costaricensis (Price et Bussing, 1967), Urocleidoides heteroancistrium (Price et Bussing, 1968), Urocleidoides anops Kritsky et Thatcher, 1974, Anacanthocotyle anacanthocolyle Kritsky et Fritts, 1970, and Gyrodaclylus neotropicalis Kritsky et Fritts, 1970 from Aslyanax fasciatus; and Gyrodactylus sp. from Gambusia yucatana Regan. Urocleidoides chavarriai, U. travassosi, U. costaricensis, U. heteroancistrium, U. anops, Anacanthocotyle anacanthocotyle and Gyrodactylus neotropicalis are reported from North America (Mexico) for the first time. These findings support the idea about the dispersion of freshwater fishes and their monogenean parasites from South America through Central America to southeastern Mexico, following the emergence of the Panamanian isthmus between 2 and 5 million years ago.