Occurrence of larval Acanthocephalus anguillae (Acanthocephala) in the Asellus aquaticus (Crustacea, Isopoda) from the River Brenta

A total of 440 specimens of Asellus aquaticus were collected from the River Brenta (northern Italy) in a single sampling in August 1992, and examined for larval helminth parasites. From the hemocoels of 14 (3.1%) individuals of A. aquaticus, 17 acanthocephalan larvae were removed: of these 15 were well-developed cystacanths of Acanthocephalus anguillae (a new geographical recording for cystacanth); not more than two larvae were found in a single host. The sex-ratio among the parasitized isopods was approximately 1:1. In more than 64% of infected A. aquaticus, the integumental pigmentation was darker than that of non-parasitized individuals. Infected isopods were never observed in amplexus, and one parasitized female specimen carried 50 eggs in its brood pouch. In hosts with well-developed cystacanths, the displacement of isopod internal organs, such as the alimentary canal, was observed. © 1994 Taylor & Francis Group, LLC.