Effects of dietary lipid on the gonad development, fatty acid composition, and histological structure of Argopecten irradias

Abstract:

A 30-day feeding experiment was conducted to investigate the effects of dietary lipid (mass fraction is 7%, 10%, 14%, and 17%) on the gonadal development, fatty acid composition, and tissue structure of Argopecten irradias. Four isonitrogen (mass fraction is 47% crude protein) feeds were formulated with the supplementation of graded levels of fish oil (mass fraction is 0%, 3%, 6%, and 9%). The scallops fed Nitzschia closterium f. minutissima served as control group. The scallops [initial body mass:(40.79±1.70 g)] were stocked in glass reinforced plastic tank (1 000 L), and each diet was randomly allocated to three groups of scallops. (Result) Mortality rate was not significantly affected by dietary lipid, but mortality rate of control group was significantly lower than feed treatment (P< 0.05). The gonadosomatic index (GSI) showed an increased tendency first and then decreased with the increase of dietary lipid. The highest GSI was observed in scallops fed F14 diet, with no significant difference from control group (P> 0.05), significantly higher than the initial period (P<0.05). The highest moisture content of female gonad was observed in scallops fed F10 diet, significantly higher than that fed F17 diet (P< 0.05). The lipid content of female gonad was significantly higher than male gonad (P< 0.05). The SFA, MUFA, n-3PUFA, DHA, and EPA contents were significantly affected by dietary lipid (P< 0.05), and the highest content was observed in F14 or F17. The gonadal tissue sections showed that the follicular cavity was filled with oocytes and seminocytes. It was feasible to partially replace unicellular algae with formulated feed and the gonad could be developed to the requirement of seedling. These results above suggest that the optimal dietary lipid level for Argopecten irradias is about 14%.