Insect meal based diets for clownfish: Biometric, histological, spectroscopic, biochemical and molecular implications

Basic nutrition for tropical fish is undeniably lacking, mainly due to the concentration of research efforts on and funding for food fish species. However, as the marine ornamental aquaculture industry continues to grow and expand, it is now essential to direct nutritional research to mitigate the current lack of information related to feeds specifically formulated for ornamental fish. Due to a minimal environmental impact, compared to most conventional feed commodities, insects deserve a growing attention as candidate ingredient for aquafeeds and Hermetia illucens, the black soldier fly, is presently one of the most promising insect species. The aim of the present study was to formulate new insect based diets and to evaluate, through a multidisciplinary approach including morphological, biochemical, spectroscopic and molecular analysis, the major biological responses of Amphiprion ocellaris juveniles fed on these diets over a 106 days experimental period. Biometry did not reveal differences in survival and growth; fish fatty acid composition was influenced by the diets. Real-Time PCR analyses on genes involved in fish growth (igf1, igf2 and mstn), lipid metabolism (pparα and pparβ) and stress response (gr and hsp70), did not show significant differences among groups. Histology showed a normal intestinal mucosa and liver parenchyma in all experimental groups. Lower amounts of lipids and proteins, together with a higher amount of glycogen, were detected by FTIR in the liver of clownfish fed on diets including higher insect meal amounts.