THE REPRODUCTION STRATEGY OF OYSTER OSTREA-EDULIS L FROM THE BIOCHEMICAL POINT-OF-VIEW

1. Influence of the biochemical composition of food (four species of micro-algae and one mixture) on the biochemical composition of gonads and larvae of O. edulis (total protein, lipid, carbohydrate, ash content, neutral and polar lipid class composition, amino acid composition and fatty acid composition of total, neutral and polar lipids) and the size of newly released larvae have been investigated. 2. Percentage of total lipids and triacylglycerols in gonads depends on that in algae (r = 0.52 and 0.69 accordingly). 3. Gonads rich in lipids had a higher level of triacylglycerols, phospholipids, polar lipids and a lower value of the ratio phosphatidylethanolamine/phosphatidylcholine (PE/PC) than gonads with a low lipid content. 4. Amino acid composition of gonads depends on that of food, in this case, essential acids are preferentially accumulated (Asp acid, Ser, Ala, Cys, Tyr and Pro) and two non-essential (Thr and Lys). 5. Fatty acid composition of total lipids of gonads was rather stable; except for the two essential acids 20:5w3 and 22:6w3, their percentage depends on that of food (r = 0.65 and 0.65 accordingly). Fatty acid composition of neutral lipids was more diverse (in number and degree of variety) as compared to polar lipids. 6. Larvae released from oysters with gonads rich in lipids had a higher percentage of lipids, triacylglycerols, size and a lower ash percentage and value of ratio PE/PC, as compared to larvae from gonads with low lipid content. Total lipid and triacylglycerol contents in gonads correlate rather well with those in larvae (r = 0.77 and 0.47 accordingly). 7. Phospholipid class composition of larvae strongly depends on that of gonads. All the correlations are high and positive in character (except for phosphatidylinositol). 8. Amino acid composition of larvae depends on that of gonads and, as in the case with gonads, the same essential acids are accumulated in the first place. 9. Fatty acid composition of total lipids of newly released larvae was rather stable and independent on that of gonads except for total polyunsaturated acids (r = 0.70) and 20:5w3 (r = 0.65). Fatty acid composition of neutral lipids was lesser diverse (in number and degree of variation) as compared to polar lipids.