On the basis of morphological and molecular data, Walteriella n. g. is proposed to accommodate the dactylogyrid parasites Walteriella conica n. sp. (type-species) from the gills of Platynematichthys notatus (Jardine) (type-host) and Brachyplatystoma juruense (Boulenger), and Walteriella ophiocirrus n. sp. from the gills of Platystomatichthys sturio (Kner) (type-host), all fish host belonging to the Pimelodidae collected in the Peruvian Amazonia. Species of the new genus are distinguished from other dactylogyrids infecting Neotropical catfishes by the presence of a folded germarium, a male copulatory organ basally articulated to the accessory piece, a cone-shaped seminal receptacle, and ventral and dorsal bars with projections directed anteriorly. Both species of the new genus form a strongly supported lineage closely related to Dactylogyridae gen. sp. 13, a parasite of Hypophthalmus edentatus Spix & Agassiz (Pimelodidae) in an analysis of partial sequences of the 28S rRNA gene. The clade formed by species of Walteriella n. g. and Dactylogyridae gen. sp. 13 is closely related to other dactylogyrids infecting pimelodid catfishes. Based on the morphology of its haptoral elements and copulatory complex, the species Dactylogyridae gen. sp. 13 is morphologically different from species of Walteriella n. g., but its generic assignment is still unclear.

Department of Botany and Zoology Faculty of Science Masaryk University Kotlářská 2 61137 Brno Czech Republic Institute of Parasitology Biology Centre of the Czech Academy of Sciences Branišovská 31 37005 Ceske Budejovice Czech Republic

Institute of Parasitology Biology Centre of the Czech Academy of Sciences and Faculty of Science University of South Bohemia Branišovská 31 37005 Ceske Budejovice Czech Republic

Instituto de Ecología Pesquerías y Oceanografía del Golfo de México Av Héroe de Nacozari No 480 Universidad Autónoma de Campeche San Francisco de Campeche CP 24029 Campeche Mexico

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