Luciaella ivanovae n. g., n. sp. (Eucestoda: Proteocephalidea: Peltidocotylinae), a parasite of Ageneiosus inermis (L.) (Siluriformes: Auchenipteridae) in Argentina.

Luciaella ivanovae n. g., n. sp. (Proteocephalidea: Peltidocotylinae) is proposed to accommodate a new cestode from a siluroid fish, the manduvé Ageneiosus inermis (Linnaeus) (syn. A. brevifilis Valenciennes) (Auchenipteridae) from the Colastiné River, a tributary of the Paraná River, in Argentina. The new genus is placed in the Peltidocotylinae because it has a medullary ovary with projections into the dorsal cortex, cortical vitelline follicles and testes, a cortical uterine stem, and uterine branches penetrating the medulla and usually as far as the dorsal cortex. Luciaella can be distinguished from all other peltidocotyline genera by the following combination of characters: a quadrangular scolex with four biloculate suckers, each of which has a cap-peak-like structure situated on the anterior margin; the absence of a metascolex; vitelline follicles arranged in two lateral rows which are crescent-shaped in transverse section; testes distributed in two dorsal fields connected anteriorly and sometimes posteriorly; and a vagina which is always anterior to the cirrus-sac and overlaps the convoluted vas deferens. Filiform microtriches are present on all tegumental surfaces, with short filiform microtriches on the scolex and long filiform microtriches on the proliferation zone and on both immature and mature proglottides. The diagnosis of the Peltidocotylinae Woodland, 1934 given by Rego (1994) is amended. L. ivanovae is the fourth proteocephalidean described from A. inermis and the third recorded in this fish host from Argentina.