Saprolegniaceae infection in white-clawed crayfish (Austropotamobius pallipes complex) in an experimental hatchery in northern Italy.

Mortality of white-clawed crayfish, Austropotamobius pallipes complex, occurred in a Northeastern Italian trout hatchery during an intensive breeding trial between autumn 2004 and summer 2005. The crayfish were submitted to postmortem histological, microscopical, mycological and bacteriological examinations. Saprolegniaceae were isolated from gills, legs and abdomen of all crayfish samples, while Fusarium sp. was found in only one specimen. The ectosymbiotic peritrichous ciliate protozoan, Cothurnia sieboldii, and a clitellate annelid, Branchiobdella hexodonta, were found on gill filaments and exoskeletons of all specimens examined. Fungal hyphae were observed on gonopods, abdominal exoskeletons, eye stalks and leg joints. These infections were occasionally observed causing heavy inflammatory lesions in skeletal muscle and green gland, and necrosis in the hypoderm; in some cases the hyphae were surrounded by melanin. The cause of mortality was attributed to a Saprolegniaceae infection, induced by poor water quality conditions.