Agamermis decaudata Cobb, Steiner & Christie, 1923 (Nematoda : Mermithidae) parasitizing Castnia dedalus isopods in Cordoba, Argentina

A population of Agamermis decaudata from Cordoba, Argentina, is described o n the basis of its morphology and morphometrics and is compared with other populations of the species. Variability occurring in morphological and morp hometric characters is analyzed and provides new data on the nematodes' bio logy. The morphological characters correspond to those known for the specie s, but for some characters the mean values are smaller and the morphometric limits greater than those previously published. Variability of these chara cters was larger in males than in females. The nematodes were found parasit izing Castnia dedalus, which is the first record of isopods being attacked by members of the genus Agamermis. The nematode had not previously been rec orded from Cordoba and this occurrence extends the known distribution of th e genus.