Experimental study of Fusarium solani: infections in Astacus leptodactylus and Pacifastacus leniusculus (Crustacea, Decapoda)

Abstract

A cuticular infection of crayfish Astacus leptodactylus, characterized by the development of large brown patches on the abdomen, was investigated. This 'brown abdomen disease' is caused by the fungus Fusariurn solani. The mycosis was reproduced under experimental conditions in artificially wounded A. leptodactylus and North American crayfish Pacifastacus leniusculus. The importance of wounds and of their location on the crayfish body to the development of the infection was determined. Superficial scratches whether dorsal or ventral generally have little or no effect on either species. Haernorrhagic punctures on tergites and on arthrodial membranes however led to mortalities amongst individuals exposed to F. solani P. leniusculus was found to be markedly more resistant to infection than was A, leptodactylus. Histological and ultrastructural investigations showed the importance of haernolymph exudates at the surface of wounds in the success of infection. These, together with toxicological experiments, demonstrated that crayfish death in F. solani infections is caused by physiological disturbances resulting from interference with the moulting process, together with the presence of toxic metabolites produced by the fungus.