DEVELOPMENT OF YOLK COMPLEX, LIVER AND ANTERIOR INTESTINE IN PIKE-PERCH LARVAE, STIZOSTEDION-LUCIOPERCA (PERCIDAE), ACCORDING TO THE 1ST DIET DURING REARING

Pike-perch Stizostedion lucioperca larvae fasted or given two diets (a rtificial feed, zooplankton) were studied by transmission electron mic roscopy and using specific cytological dyes. The objective of this wor k was to assess the changes in the yolk sac, liver and anterior intest ine following the mouth opening stage (95-degrees-C.d, day 5 - 5.8 mm) from endo- to exotrophy periods. The yolk sac included a syncytial en velope closely bound to the proteinaceous vitellus and the oil globule . Its development was similar to that observed in trout (Oncorhynchus mykiss and Salmo fario trutta) and sea-bream (Sparus aurata), but with out vitellus fragmentation into platelets. Vitellus resorption was nev er achieved in dying larvae. From the end of the endotrophic phase onw ards, the amount of hepatic glycogen decreased. Carbohydrate disappear ed at the beginning of the exotrophic phase then increased after 220-d egrees-C.d (day 10 - 6.0 mm), mainly in zooplankton-fed larvae. Lipids from enterocytes, sinusoids and general blood stream showed a similar development. They were abundant at 95-degrees-C.d, progressively disa ppeared up to 260-degrees-C.d (day 12 -6.3 mm), and increased again fr om 350-degrees-C.d (day 16 - 6.7 mm) onwards if larvae were fed zoopla nkton. Dietary lipids did not seem to immediately replace yolk lipids despite absorption in the gut. Various hypotheses are proposed to expl ain the physiological abnormalities of this critical larval stage. Alt hough zooplankton appeared to have better nutritional qualities than t he artificial feed, these two foods proved to be quite unsatisfactory as they induced liver cell changes typical of food deficiency, general ly observed in starving larvae.