A new species of Hysterothylacium (Ascaridoidea, Anisakidae) parasitic in Zenopsis conchifer (Zeiformes, Zeidae) from Argentinean waters

Abstract

A new species of parasitic nematode, Hysterothylacium spirale sp. nov. (Ascaridoidea, Anisakidae), is described based on specimens collected from the intestine and pyloric caeca of the silvery john dory Zenopsis conchifer (Lowe) (Zeiformes, Zeidae), from the Argentinean Shelf (35°05´-40°46´S, 53°03´-58°07´W). Among the 66 valid species described so far in the genus, the new species most closely resembles H. zenis (Baylis, 1929). Both species, apparently specific for fishes of the family Zeidae, share the shape of the dorsal lip, the long expanded lateral alae originating from subventral interlabia and the ornamentation of the tail tip, as well as general morphometry. The combination of these shared features distinguishes both species from all congeners so far known. However, the new species is distinguishable from H. zenis by having shorter interlabia, and consequently the lateral alae originating more posteriorly, shorter spicules, a smaller number of postcloacal papillae and the presence of two pairs of double postcloacal papillae.