Fatty acid composition in Mytilus gallo provincialis organs: Trophic interactions, sexual differences and differential anatomical distribution

Abstract

The fatty acid (FA) profiles in neutral lipids (NLs) and polar lipids (PLs) of the gills, digestive gland and mantle of female and male mussels Mytilus galloprovincialis (cultured in Ría de Arousa, Galicia, NW Spain, and studied during an annual seasonal cycle) reflected dietary, sexual and functional differences. Seasonal differences arose from variations in the trophic environment, with diatom FA biomarkers dominating during the spring bloom, biomarkers from dinoflagellate-rich diets dominating during winter mixing, and a combination of both sources apparent during the summer and autumn transitory periods. The influence of diet was more pronounced in the NL (energetic reserves) than in the PL (structural membrane components) FA signatures of all organs, although dietary changes were mirrored more clearly in the digestive gland. Differences between males and females were restricted to the mantle and probably resulted from gonadal ripeness during spring. The NL and PL FA profile of the mantle was characterized by the abundance of 14:0, 16:0 and 16:1n-7 in females and predominance of 18:0, 18:3n-3 and 22:6n-3 in males, suggesting that each gender has distinct energetic and structural requirements during gametogenesis. Lipids containing alkenyl ethers or non-methylene interrupted (NMI) FAs were mostly found in the PLs of the gills and the mantle, supporting their role as structural and functional components in the membranes of organs directly exposed to physicochemical fluctuations. Competition between NMI and polyunsaturated fatty acids (PUFAs) was only evident in the mantle, suggesting that deficiencies in PUFAs might provoke de novo bio synthesis of NMI to satisfy reproductive demands.