Transition from endogenous to exogenous nutritional sources in larval Black Sea turbot Psetta maxima

Early growth, yolk and oil globule absorption, early morphological developm ent and initial feeding were studied in the Black Sea turbot Psetta maxima. Based on energy transition and morphological development, the nutritional transition process from enclogenous to exogenous sources was divided into s ix phases: (i) primordial phase (from hatching to approximate to 30 h after hatching, HAH); (ii) organogenesis phase (to approximate to 90 HAH); (iii) onset of feeding (to approximate to 110 HAH); (iv) early feeding (to appro ximate to 190 HAH); (v) intensified feeding (to approximate to 230 HAH); an d (vi) completion of oil globule absorption (to beyond 345 HAH). Based on c omparisons with early life stage features of other marine species, the turb ot larvae were shown to possess the following characteristics: (i) oil glob ule remaining for a long period, resulting in an extended mixed feeding per iod; and (ii) feeding rate extremely high in larvae immediately following f inal absorption of the oil globule. These features in early turbot larvae w ere regarded as advantageous for survival in a rearing condition, although the coincidence of initial feeding with completion of yolk absorption signa led a period of leveled-off growth rate.