Lipid composition of Symphodus ocellatus (Perciforme : Labridae) in the north-western Mediterranean: influence of two different biotopes
Résumé
The lipid content and fatty acid composition of the small common wrasse Symphodus ocellatus was analysed within two populations located in very different biotopes on the French shore: a Caulerpa taxifolia meadow located in Cap Martin and a Posidonia oceanica bed located in Villefranche. Polar lipids represented 82-90% of the total lipid in adult female livers, gonads and in eggs. Cholesterol in gonads and eggs and triacylglycerols in livers were the dominant neutral lipids. Differences in lipid classes were found in livers between the two populations, but not in their gonads and eggs. Moreover, a quantitative difference in total lipid content was evident. Young fish living on the C. taxifolia meadow in winter had 21% less lipid than those living on the P. oceanica bed. The populations of S. ocellatus showed differences between triacylglycerol versus phospholipid fatty acid compositions and between gonad versus liver fatty acid compositions. Moreover, a significant difference was found between both populations in their liver triacylglycerol fatty acid compositions, suggesting a difference in diet. Gut content analysis supported this hypothesis as it showed important differences in the ingested preys between the two populations in January (planktonic vs. benthic, frequency of isopods) and in June (frequency of gastropods). Thus, we found that the fish populations from Villefranche and Cap Martin showed significant differences in body lipids due to different nutritional habits.