Seasonal changes of the fatty acid composition in the hepatopancreas and vitelline gland of the gastropod Onchidium struma

We analysed the fatty acid composition of the hepatopancreas and vitelline gland of Onchidium struma by capillary gas chromatography. Our results showed that there are 22 fatty acids (FAs) in the hepatopancreas and 23 in the vitelline gland, all of which were even carbon fatty acids and long chain fatty acids. C16:0, C16:1n-7, C18:0, C18:1n-9, C20:1n-9, C20:4n-6 and C20:5n-3 were the principal FAs. In the hepatopancreas, 4 saturated fatty acids (SFAs; 29.53-35.44%), 4 monounsaturated fatty acids (MUFAs; 30.73-34.34%) and 14 polyunsaturated fatty acids (PUFAs; 29.33-36.72%) were found. In spring, summer, autumn and winter, FA numbers in the hepatopancreas were 22, 19, 18 and 20, respectively. C22:2NIMD and C22:4n-6 were only detected in spring. The content of C18:1n-9, C18:2n-6, C20:5n-3 and Sigma n3 was remarkably different with season. In the vitelline gland, 4 SFAs (26.33-38.03%), 4 MUFAs (18.97-32.67%) and 15 PUFAs (31.92-52.51%) were found. In spring, summer, autumn and winter, FA numbers in the vitelline gland were 23, 17, 18 and 18, respectively. C20:0, C22:2NIMD, C22:3n-3 and C22:4n-6 were only detected in spring. The content of C18:1n9, C18:2n-6, C18:3n-3, C20:4n-3, C20:4n-6, C20:5n-3 and Sigma n3 was remarkably different for different seasons. From spring to summer, C20:4n-6, C20:5n-3 and C22:6n-3(DHA) in the vitelline gland decreased significantly, while C18:2n-6 and C18:3n-3 increased. These results showed that the seasonal variation of FAs is clearly related to the reproductive cycle, and suggested that FA in the hepatopancreas may be transferred to the vitelline gland of O. struma during maturation.