Alterations histologiques observees chez des larves de turbot (Scophthalmus maximus L.) en elevage intensif

Abstract Histological observations were made on 406 turbot larvae, 6–15 days old. The specimens were sampled from seven cultures in which high mortalities occurred. The larvae dying between day 6 and day 8 are usually thin and present a regression of the digestive tract with atrophy and/or desquamation of the mucosa of the digestive tube. Later mortalities (day 9 to day 15) appear in specimens which are developed to a certain extent and therefore have already ingested food. Again, atrophy and desquamation of the digestive tract are observed in larvae which have stopped feeding. As in the previous case, muscular degeneration, dystrophy of the swim bladder and glomerular atrophy are noted. Between day 10 and day 14 (after Artemia are substituted for Brachionus as live prey) some larvae become abnormal, with a yellowish coloration of the head and abdomen. At this time the digestive tube is full but the intestinal wall exhibits areas of degeneration and the heart presents ventricular hyperplasia. Finally, in one of the populations, all the examined moribund specimens at day 8 had extensive hyperplasia of the intestinal epithelium and heart. No infectious, parasitic or dysplasic factors having been detected, the alterations observed are attributed essentially to inadequate quality of the prey, either in size or nutritional value.