UTILIZATION OF YOLK RESERVES DURING POSTEMBRYONIC DEVELOPMENT IN 3 TELEOSTEAN SPECIES - THE SEA BREAM SPARUS-AURATA, THE SEA BASS DICENTRARCHUS-LABRAX AND THE PIKE-PERCH STIZOSTEDION-LUCIOPERCA

A comparative study of the use of yolk reserves during post-embryonic development was performed on three teleostean fishes of aquacultural i nterest: the sea bream Sparus aurata, the sea bass Dicentrarchus labra x, and the pike-perch Stizostedion lucioperca. The first part of the w ork was devoted to the structural development of the periblast, the vi tellus and the oil globule during the endotrophic and endo-exotrophic phases of larval life. Observations using transmission electron micros copy revealed a perivitelline circulation system closely related to th e liver, and suggested an important function of the periblast in the u tilization of reserves. In the second part of the study, cytochemical reactions revealed the way in which the reserves are resorbed. Glycoge n contained in the periblast at hatching was utilized during the endot rophic period. The successive appearance of lipoprotein particles in t he periblast endoplasmic reticulum, Golgi apparatus, and perivetelline circulation zone is consistent with the mobilization of yolk and oil globule components. Comparison of fed and fasting individuals revealed that fasting tended to slow down rather than increase the utilization of reserves.