Effects of salinity on digestive protease activity in the euryhaline sparid Sparus aurata L.: a preliminary study

Bioactive additives in food to improve growth, development and reproductive success of crustaceans have received little attention. In the present study, the effects of carotenoid and vitamin A injections were characterized and correlated to the ontogenic development of oocytes in female Cherax quadricarinatus reproducers. During an acclimation period, 250 C. quadricarinatus females were fed a basal diet devoid of carotenoids and retinoids. Four treatments were administered by injection: retinol palmitate (RP), (beta)-carotene, astaxanthin and vegetable oil as the control treatment. Before the experiment, total gonadic mass of organisms was obtained to determine the gonadosomatic index. Histological techniques were used to evaluate the effects of the different treatments during the primary vitellogenic phase. Retinol palmitate had the greatest inductive effect on the primary vitellogenic phase and on indicators of ontogenic oocyte development. The bioactive and molecular foundations of the action of carotenoids and retinoids that actively participate during the process of nuclear signalling and differentiation of the oocyte are discussed, considering these compounds as essential nutritional additives during gonadic maturation.