UTILIZATION OF YOLK FUELS IN DEVELOPING EGGS AND LARVAE OF EUROPEAN SEA BASS (DICENTRARCHUS-LABRAX)

Developing eggs and larvae of European sea bass (Dicentrarchus labrax) maintained in filtered sea water (40 gl(-1)) at 18 degrees C, were me asured for oxygen uptake, contents of free amino acids (FAA), protein, fatty acids (FA), and volumes of yolk-sac and oil globule. Newly spaw ned eggs had a dry weight of 90 mu g egg(-1) and an egg diameter of 1. 14 +/- 0.03 mm. The yolk was quickly absorbed during the embryonic and the early larval stages and was 95% depleted by 100 h post fertilisat ion. The depletion rates of the FAA were somewhat faster than the rate of absorption of the general yolk matter and were almost complete by 80 h post fertilisation. The oil globule was mainly absorbed after hat ching following yolk absorption, and occurred concurrently with catabo lism of FA from neutral lipids. Approximately 30% of the oil globule w as still present at the presumed onset of exogenous feeding. Overall, FAA appeared to be a significant energy substrate during the egg stage and the early yoIk-sac stage while FA from neutral lipids derived fro m the oil globule seemed to be the main metabolic fuel after hatching. Amino acids from protein seemed to be mobilised for energy in the las t part of the yolk-sac stage. This investigation supports accumulating evidence for a common sequence of catabolic substrate oxidation in ma rine pelagic fish eggs that contain oil globules. (C) 1998 Elsevier Sc ience B.V.