Fig. 5. Characteristics of the membrane lipids in mussel (M) and oyster (O) digestive glands (DG) and gills, as a function of time (left) and species and tissues (right). (A) The phospholipid to sterol ratio, (B) the unsaturation index and (C–E) the mol % of polyunsaturated fatty acids (PUFA; C), 22:6n-3 (D) and 20:5n-3 (E) in the polar lipids. Values are means ± s.e.m, N=2–6 tanks. The unsaturation index is calculated as the sum of the molar percentage of each unsaturated fatty acid multiplied by the number of double bonds within that fatty acid. Data from different overwintering temperatures were pooled as this effect was not significant. Different letters indicate significant differences.