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

The seasonal variations of fatty acid concentrations were studied during tw o consecutive years in five tissues of female dog cockles (Glycymeris glycy meris) originating from Douarnenez Bay (South Brittany, France). In all tis sues, saturated fatty acids (SFA) were the major forms of fatty acids, foll owed by polyunsaturated fatty acids (PUFA). The concentrations of monounsat urated fatty acids (MUFA) were low. The C20:0 was most often the predominan t SFA in all tissues. The total amount of fatty acids in each of the SFA, M UFA. and PUFA series underwent important fluctuations in the foot and in th e visceral mass, whereas only slight variations were recorded in the adduct or 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 concentrati ons 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 b oth on bacteria-enriched detritic matter and on phytoplankton. Important fl uctuations of fatty acids recorded in the visceral mass can, at least in pa rt, be related to certain phases of the reproductive cycle. The foot may co nstitute a temporary reserve tissue for fatty acids, especially for SFA, at the beginning of winter. (C) 1999 Elsevier Science Inc. All rights reserve d.