Echinoculture: rearing of Paracentrotus lividus in recirculating aquaculture system. Experimentations of artificial diets for sexual maturation

Abstract

Fishing effort in recent decades has led to a drastic reduction of the natural population of Paracentrotus lividus, for this reason it has become urgent the adoption of specific management policies to ensure the survival of wild In this scenario aquaculture must necessarily hold, in the near future, a central role in the politics of restoration of wild stocks. The rearing of this species aimed to restocking, is certainly desirable also because of further consideration: since the early ’80,this species has been recognized worldwide, as the most reliable biomarker (ICES 1997), and its gametes used for the preparation of biological assays for the monitoring of marine pollution. While this has resulted in P. lividus to be considered a biological model, a species widely used by researchers to study biological phenomena of scientific importance, on the other hand has product a further fishing pressure. From this comes the need to develop rearing techniques for this species for the production of gametes to be used in scientific application, to use in restocking wild population and at the same time to cope the growing market demand for gonads, much appreciated as seafood. In this research project, have been developed two protocols to ensure the maintenance of mature organisms in Recirculating Aquaculture System (RAS) and to stimulate the maturation of mature Paracentrotus lividus with test diameter ranging from 40 and 45mm. For the maintenance of mature organisms, were tested two diets: the first composed with maize and algae (macrophytes) and the second based on maize and spinach. To induce the maturation of P. lividus three artificial diets were tested: one based only algae, one consisting of maize and spinach and a pellet (Classic K®) normally used in fish farming. To evaluate the validity of the protocols used during the experimentation, were performed toxicological tests on gametes of farmed organisms (to ensure the quality of gametes in terms of sensitivity to a reference toxicant), evaluated temporal trends of gonadosomatico index (GI), evaluate the progression of maturation stages by histological examination. Through the harmonic generation microscopy (HGM) was evaluated the onset of apoptotic signals, in plutei obtained from reared organisms, potentially induced by stress conditions which are subjected in rearing system. In order to assess the health of farmed organisms, were also determined Righting Activities Coefficient (RAC). Referring to the maintenance of sexual maturity in Paracentrotus lividus in RAS, the protocol adopted has guaranteed the maintenance of mature organisms in aquaria for 4 months. Results obtained from the experimentation of artificial diets for the induction of maturation of Paracentrotus lividus in RAS have shown that Maize&Spinach diet gave the best results in terms of gonadosomatic index values (GI). Moreover, diets, administered ad libitum and in combination with a photoperiod L 10h: 14h B and a temperature of 16 ° C, were found to be suitable to stimulate gametogenesis and ensure the production of gametes for ecotoxicological tests. Harmonic generation microscopy (HGM) showed that Maize&Spinach diet, leads to the generation of plutei with high apoptotic signals and therefore not suitable for the creation of juvenile P. lividus.