Pomphorhynchus laevis in its intermediate host Echinogammarus stammeri in the River Brenta, Italy

Abstract

Infection rates of larval Pomphorhynchus laevis Mu¨ller, 1776 (Acanthocephala) were studied in its intermediate host Echinogammarus stammeriS. Karaman, 1931 (Amphipoda). Crustaceans were collected monthly, from July 1990 to July 1997, at two sites on the River Brenta (northern Italy). Of over 50,000 E. stammeri examined, more than 24% were parasitized with P. laevis larvae. The differences in the prevalence of infection between the two stations were significant. The intensity of infection varied from one to 15 acanthocephalans per host. Amphipods with multiple infections constituted 28–32% of each monthly sample. During the 7 years of investigation, the prevalence of infection typically reached its highest and lowest levels in the summer and spring months, respectively. Acanthocephalan larvae showed no preference for host sex. Infected ovigerous females of E. stammeri were found carrying eggs or juveniles in their brood pouches, but had fewer and smaller eggs. Pomphorhynchus laevis larvae co-occurred with Acanthocephalus clavula (Dujardin, 1845) and also with the tapeworm Cyathocephalus truncatus (Pallas, 1781) in the same host.