Occurrence of Acanthocephalus clavula (Acanthocephala) in Echinogammarus pungens (Amphipoda) from the River Adige.

Cystacanths of Acanthocephalus clavula Dujardin 1845 (Acanthocephala) were found in the hemocoels of naturally infected Echinogrammarus pungens M. Edwards 1840 (Amphipoda). Crustaceans were collected in Porto Frossone, an estuarine locality of the River Adige. Only 3 out of 562 E. pungens specimens were infected by A. clavula cystacanths; the larvae were enclosed in a thin acellular envelope. Infected amphipods were all females, and their total length was greater than that of uninfected females. Moreover, adult specimens of this acanthocephalan were found in the alimentary tract of Anguilla anguilla (L.) eels sampled in the crustacean collecting site. A description of cystacanths and their stages of development is reported here.