Changes in tissue concentrations of the vitamins B1 and B2 during reproductive cycle of bivalves: Part 1: The scallop Pectenmaximus

Abstract

Vitamins B1(thiamin) and B2 (riboflavin) in eggs of the scallop Pecten maximus are highly utilized during larval development. Possible storage of these vitamins, for later transfer to gonads and eggs, was studied over the natural reproductive cycle of the scallop. Vitamin concentrations were measured during hatchery conditioning at three periods of the year. Vitamin B1 was found mainly in muscle, gonad and eggs, while B2 was detected in the digestive gland, gonad and eggs. They varied simultaneously in the three organs during the annual cycle. Two main peaks were observed for digestive gland and gonads in spring and summer. The first peak corresponded to vitellogenesis and decreased in gonads in June as the scallops spawned and the vitamins were lost with the eggs. The second peak was interpreted as vitamin storage in gonad tissue in fall. The large vitamin decrease occurring from November to February coincided with gonial mitoses observed by histology. Possible high utilisation of thiamin and riboflavin during winter was supported by hatchery conditioning at three periods during the year: during the same winter period, when broodstock were fed a high-vitamin diet, vitamin levels stayed low in all organs, as vitellogenesis was in progress. However, in spring and summer vitamin incorporation increased. We concluded that attention should be paid to winter-conditioning diets, as riboflavin and thiamin, even when provided at high levels in the food, did not accumulate in organs, suggesting intense utilisation when mitoses in the gonads take place.