HYPERVITAMINOSIS A DURING VERTEBRAL MORPHOGENESIS IN LARVAL JAPANESE FLOUNDER

experiments were conducted in order to examine the effect of a high am ount of vitamin A (VA) given through Artemia on the vertebral developm ent of larval Japanese flounder Paralichthys olivaceus. Ten-day-old fl ounder larvae were cultured for 30 days. In Experiment I, larvae were fed on Artemia enriched in a 10-liter medium containing 100 mg VA palm itate (1 mu g VA palmitate=1 IU VA), starting from different larval st ages until metamorphosis, or at a different rearing period. In Experim ent II, critical larval periods (three days) of feeding Artemia enrich ed in a 10-liter culture medium containing 100 mg VA palmitate on vert ebral development were examined. Enrichment of Artemia with 100 mg VA palmitate in a 10-liter culture medium resulted in 1069 and 918 IU VA per g Artemia (dry basis) in Experiments I and II, respectively. Feedi ng on Artemia containing these high VA concentrations caused the compr ession of vertebrae in flounder. This vertebral deformity was found to occur when larvae were exposed to these high dosages of VA during the G stage (during day 25-27, about 11 mm of total length) in which noto chord segmentation took place. The effect of high dosage of VA was eve n more distinct in fish receiving VA for a longer period, a high incid ence of deformity being accompanied by retardation of growth.