Variations of fatty acid contents in selected tissues of the female dog cockle ( Glycymeris glycymeris L., Mollusca, Bivalvia) during the annual cycle

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The seasonal variations of fatty acid concentrations were studied during two consecutive years in five tissues of female dog cockles ( Glycymeris glycymeris) originating from Douarnenez Bay (South Brittany, France). In all tissues, saturated fatty acids (SFA) were the major forms of fatty acids, followed by polyunsaturated fatty acids (PUFA). The concentrations of monounsaturated fatty acids (MUFA) were low. The C20:0 was most often the predominant SFA in all tissues. The total amount of fatty acids in each of the SFA, MUFA and PUFA series underwent important fluctuations in the foot and in the visceral mass, whereas only slight variations were recorded in the adductor muscles, the tunic coat and the mantle. A main peak of SFA was measured in the foot at the beginning of winter and peak values of SFA were recorded in the visceral mass in April, June and in autumn. The highest concentrations of fatty acids were measured in the visceral mass, in April just before the first and main annual spawning period which occurs in late April or in May, depending of the year. Our results suggest that G. glycymeris feeds both on bacteria-enriched detritic matter and on phytoplankton. Important fluctuations of fatty acids recorded in the visceral mass can, at least in part, be related to certain phases of the reproductive cycle. The foot may constitute a temporary reserve tissue for fatty acids, especially for SFA, at the beginning of winter.