VITAMIN REQUIREMENTS IN GREAT SCALLOP LARVAE

Vitamins were analysed in food (microalgae) and larvae of great scallo p, Pecten maximus, during larval development. Microalgae used to feed larvae in hatcheries show great variability in their vitamin compositi on depending on both the species and culture condition (phase of growt h). The microalgae used to feed Pecten maximus larvae were rich in vit amins; their content compared with diets used in fish culture appeared sufficient, with the possible exceptions of pyridoxine, biotin and pa ntothenic acid. Vitamins in bacteria, isolated from the larval rearing tank were also analysed, as they can also contribute to the diet. Vit amin B-12, alpha-tocopherol and beta-carotene were detected in very lo w concentration in bacteria; however, some bacterial strains were rich in pantothenic acid, and the pattern of other vitamins was similar to that from microalgae. The presence of bacteria can complement the die t in panthothenic acid, as it has been demonstrated that bacteria are ingested by larvae. The vitamin content of Pecten maximus larvae was a nalysed from the second day after hatching to just before metamorphosi s. The content of some vitamins, ascorbic acid (C), alpha-tocopherol a nd beta-carotene, increased during larval development, suggesting that their requirement was satisfied. However, thiamin and riboflavin decr eased during larval development and further studies, possibly using mi croencapsulated vitamins supplements, are needed to determine whether these vitamins are limiting during larval development.