Insects are considered as an alternative and sustainable ingredient for feed production. In this study, Hermetia illucens (Hi) prepupae (fed on coffee roasted by-product added with 10% Schyzochytrium sp., a marine protist rich in polyunsaturated fatty acids) was processed into meal and included at graded levels in five experimental diets to replace dietary fish meal (0, 25, 50, 75, 100%) offered to zebrafish (Danio rerio) as experimental model. The fatty acids (FAs) profile of fish larvae (20 days), juveniles (2 months, deprived of the viscera) and adults (6 months, male and female, deprived of the viscera) specimens was investigated to evaluate the impact of dietary FM replacement with full-fat Hi prepupae meal. For the first time, the quantification of FAs in Danio rerio, performed by gas chromatography-mass spectrometry, was computed in absolute terms (mg 100g-1 dw), identifying the real variation in the content of any single FA. In fish, quantified total FAs in larvae, juvenile, adult male and adult female were 134±2, 235±8, 266±3 and 266±8 mg g-1 dw, respectively. With respect to zebrafish fed the control diet, specimens fed diet with increasing level of Hi prepupae meal showed significantly higher content of saturated and omega6 FAs, and significantly lower content of poly-unsaturated and omega3 FAs, reflecting partially the FAs composition of the administered diets. At the same time, the docosahexaenoic/eicosapentaenoic acid ratio increased significantly. Moreover, adult female showed a higher content of PUFA with respect to adult male, which could be justified by the needs of physiological reproductive processes. The principal component analysis demonstrated that the FAs composition in Danio rerio depends on both the life stage and the diet.
