New species of Guidus Ivanov, 2006 (Cestoda: Phyllobothriidea) from Bathyraja magellanica (Philippi) from the Patagonian Continental Shelf of Argentina

Abstract

Specimens representing two new species of Guidus were collected from the Magellan skate (Bathyraja magellanica) in the Patagonian Continental Shelf of Argentina, Southwestern Atlantic Ocean. Guidus francoi sp. n. and Guidus magellanicus sp. n. differ from their congeners by a particular combination of features including type of bothridia, worm length, number of testes, and distribution of vitelline follicles. Guidus francoi sp. n. is distinguished from G. magellanicus sp. n. by having fewer proglottids, fewer testes and a higher ratio between the cirrus sac length and the proglottid width. The microtrix pattern of species of Guidus from the Southwestern Atlantic is described, based on specimens of Guidus francoi sp. n., Guidus magellanicus sp. n., and newly collected specimens of G. argentinense. These three species share the presence of wide aristate gladiate spinitriches on the proximal bothridial surface, narrow gladiate spinitriches on the bothridial rim, and filitriches on the distal bothridial surface. The diagnosis of Guidus is revised to include several features exhibited by the new species (i.e., presence of bothridial indentations and bothridial stalks, distribution of vitelline follicles, and eggs grouped in cocoons). The discovery of G. francoi sp. n. and G. magellanicus sp. n. from B. magellanica increases the number of species of Guidus collected from batoids in the Southwestern Atlantic from one to three. The specificity exhibited by the species herein described reinforces the tight association between Guidus and Bathyraja hosts.