Developmental changes in multiple oil globules of Japanese sea bass eggs

In the intensive culture of fish an understanding of indicators of fish egg quality is important. Eggs of Japanese sea bass frequently are observed to have multiple oil globules; however, quality of these eggs relative to egg s with a single oil globule is not known. This paper describes development of Japanese sea bass eggs with multiple oil globules: developmental changes in the percentage of multiple oil globule eggs, oil volumes, hatching rate s and the anomaly rates in eggs and larvae. Early blastula-stage eggs had 1 -15 small oil globules and the percentage with multiple oil globules varied from 30.9 to 100% depending on batches. Fusion of oil globules occurred du ring the optic vesicles stage and in most cases number of globules decrease d from multiple to single by 1-3 hours before hatching. Volume of oil in si ngle oil globule eggs was essentially the same as the sum of integrated vol umes of all small oil globules present during the early blastula stage. Mor phological features of 50 larvae/day hatched from multiple oil globule eggs were observed from hatching to 14 days after hatching. Hatching rates from multiple oil globule eggs were high (ca. 80%) and the number of anomalous newly hatched larvae was negligible (ca. 5%). Two anomalous larvae were obs erved with one oil globule in the body cavities 7 and 13 days after hatchin g. These results suggest that multiple oil globules eggs of Japanese sea ba ss can be useful for intensive seedling production.