Biochemical profile of the native seaweed fly Fucellia maritima (Haliday, 1838) (Diptera: Anthomyiidae) reared on five different substrates

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Abstract The sustainability of aquaculture production is crucial for the industry’s long-term viability. Diversification of feed ingredients is a key component in achieving this sustainability. Considered a promising alternative to traditional feed ingredients, terrestrial insect meals often lack sufficient n-3 polyunsaturated fatty acids (PUFA). This study explores the potential of marine insect species, specifically evaluating the influence of five different substrates on the growth and composition of the European native seaweed fly, Fucellia maritima. The substrates tested include a brown seaweed (Fucus sp.), a green seaweed (Ulva sp.), a red seaweed (the invasive Agarophyton vermiculophyllum), the invasive freshwater hyacinth (Eichhornia crassipes), and fish processing waste (codfish Gadus morhua frames). Results show no significant difference in the number of individuals per substrate, although Fucus sp. had a higher total number of individuals completing their life cycle. In contrast, feeding on codfish frames resulted in a lower number of completed life cycles, while E. crassipes led to no survival. Protein content in adult flies ranged from 55.2% to 56.7%, and in pupae, it ranged from 46.1% to 48.7% across different feeding substrates. Notably, pupae fed with Ulva sp., exhibited the highest protein content at 48.7%. Lipid content in adult flies ranged from 10.0% to 13.0%, while in pupae, it ranged from 8.8% to 11.4%. Codfish frames had the highest lipid content in both pupae (11.4%) and adults (13%). The most abundant fatty acid in Fucus sp. – fed pupae and adult flies was oleic acid (18:1 n-9), while palmitoleic acid (16:1 n-7) dominated in other treatments. It is worth highlighting that docosahexaenoic acid (22:6 n-3) was reported for the first time in a seaweed fly, namely when supplied with fish processing waste. These findings suggest that Fucellia maritima may be a promising complementary ingredient for formulating marine aquafeeds.