Thalassornectes dendrocygnae new species (Acari:Hypoderatidae) from the black-bellied whistling-duck (Aves:Anseriformes; Dendrocygnidae).

A new species of hypoderatid deutonymph is described from the subcutaneous adipose tissues of the black-bellied whistling-duck, Dendrocygna autumnalis (L.), from Texas. Thalassornectes dendrocygnae n. sp. is most similar to thalassornectes rwandae Fain from the white-backed duck, Thalassornis leuconotos Eyton, in Africa. The new species is distinguished by a complete genital apodeme, the interrupted pattern of midventral cuticular sclerotization between coxal fields II and III, the dense cuticular sclerotization of the posterior idiosoma, and the long filiform seta d5, which is longer than the other idiosomal setae. In T. rwandae, the anterior and posterior parts of the genital sclerite are separated in the middle, the pattern of midventral cuticular sclerotization is continuous in the midventer, there is no dense sclerotization in the posterior idiosoma, and seta d5 is not figured (broken or absent?). There also are minor differences in chaetotaxy and solenidiotaxy of legs I and III of these 2 species. T. dendrocygnae is only the 2nd species of hypoderatid described from the host order Anseriformes. The 2 Thalassornectes spp. are described exclusively from each of the 2 genera in the host family Dendrocygnidae, respectively. Reevaluation of the suite of characters used to differentiate subgenera in the genus Thalassornectes indicates that Thalassornectes Fain, Rallidectes Fain, and Alcidectes Pence & Hoberg should be considered invalid.