Lipid composition during sexual development of the noble crayfish Astacus astacus and effect of a fungal infection

Previous published results (Hall et al., 1995) showed that two plasma proteins involved in the immune response in the crayfish (Pacifastacus leniusculus) are lipoproteins, suggesting an apparent functional association between lipid transport and the immune response system in crustaceans. The crayfish Astacus astacus is sensitive to a disease caused by the fungus Aphanomyces astaci, which is responsible for high mortalities in the natural environment. Since vitellogenesis is accompanied by a massive accumulation and transport of lipids to ovaries, the present study examines the effect of the crayfish plague fungus A. astaci on lipid transport during sexual development in the crayfish A. astacus. Comparison of the plasma lipid composition between animals sampled before and at the end of the ovarian development cycle revealed that mature females contained more lipids than males or immature females. The high-density lipoprotein (HDL) hemolymph fractions contained four to seven times more lipids than the very high-density lipoprotein (VHDL) fractions; triacylglycerols (TAG) were detected only in the HDL of females. There were no significant changes in hemolymph lipid levels in vitellogenic females subjected to an experimental fungal infection. However, in males exposed to the same experimental conditions, there was a significant decrease in phospholipids (PL) concomitant with an increase in diacylglycerols (DAG) and cholesterol (CH). No differences were observed in the lipid content of either the hepatopancreas (of males and females) or the ovaries due to infection, except a slight decrease in the ovarian PL level. Clotting protein was found relatively more abundant in plasma samples obtained from infected animals after subjecting them to polyacrylamide gel electrophoresis under native conditions. The results of the present study suggest that long-term exposure to a sub lethal dose of the fungus may allow in future studies, a better evaluation of the effect of an infection on lipid composition in shrimp plasma and tissue samples.