Morphological, physiological and biochemical parameters characterizing theover-ripening of rainbow trout eggs

In rainbow trout (Oncorhynchus mykiss) freshly ovulated eggs and over-ripen ed eggs which had been retained in the coelomic cavity for 7, 14 and 21 day s were investigated in aspects of morphology, physiology and biochemistry. Egg viability was significantly reduced from 85.9 +/- 16.4% in freshly ovul ated eggs to 25.1 +/- 21.9% in over-ripened eggs which had been retained in the coelomic cavity for 21 days. Further during over-ripening in the ovari an fluid the pH significantly decreased, while the levels of proteins, of e sterified and non esterified fatty acids and the activities of aspartate am inotransferase and acid phosphatase significantly increased. Also egg param eters changed: the wet weight of the unhardened eggs increased, the weight increase during hardening and the levels of esterified and of non esterifie d fatty acids significantly decreased. In freshly ovulated eggs the yolk co nsisted of a homogenous mass and the perivitelline space was small, but in over-ripened eggs the yolk was non homogenous with numerous vesicular inclu sions and the perivitelline space was enlarged. When freshly ovulated eggs were incubated in water the cortical reaction was detectable within 5 min, in over-ripened eggs hardly no extrusion of cortical vesicles was visible a nd the width of the perivitelline space was very irregular. For the investigated freshly ovulated and over-ripened samples the egg viab ility significantly correlated with ovarian fluid parameters (pH, protein, non esterified fatty acids, esterified fatty acids, aspartate aminotransfer ase, acid phosphatase) and egg parameters (weight increase during hardening , weight of the hardened eggs).