The enzymatic detoxifying system of a native Mediterranean Scorpio fish isaffected by Caulerpa taxifolia in its environment

The accidental introduction and extremely rapid growth of the tropical alga Caulerpa taxifolia in the northern coastal waters of the Mediterranean sea represents an adaptive challenge for indigenous animal and plant species. Since first being detected near Monaco, it has spread to many areas, someti mes hundreds of kilometers away from the initial site of implantation. This alga is known to produce some repulsive toxic compounds such as caulerpeny ne derivatives. In this study, specimens of Scorpaena porcus (a typical med iterranean fish) were maintained under laboratory conditions in the presenc e of this alga, and hepatic glutathione S-transferase and cytochrome P450 m onooxygenases activities of fish were examined. The collective data indicat e that the presence of Caulerpa taxifolia in the environment of these fish modifies the hydroxylation stereospecificity of hepatic microsomal cytochro mes P450 toward steroid substrates. These results reflect changes in the re lative levels of P450 isoforms in the liver and thus demonstrate the influe nce of Caulerpa taxifolia on the physiology of fish sharing space with this new alga. In addition, this phenomenon was found to be dependent on the co ntact time between the fish and the alga.