Dietary inclusion of the brown seaweed Ascophyllum nodosum modulates the nutritional composition and the gut microbiota of yellow mealworm (Tenebrio molitor, Coleoptera: Tenebrionidae) larvae

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Yellow mealworm larvae ( Tenebrio molitor, YML) are a promising nutrient source for animal feed, with their composition influenced by diet. This study examined the effects of including the brown seaweed Ascophyllum nodosum (50% dry matter) in the diet on YML nutritional quality and gut microbiota. Larvae were reared for 16 weeks on wheat bran (control, CN) or wheat bran with seaweed (AN) and harvested under fed or 24-h fasted conditions. The dietary inclusion of A. nodosum increased the levels of certain minerals, including Na (∼1.4-fold), K (∼1.2-fold), and Cu (∼8.2-fold), but lowered Mn (∼1.9-fold) contents of larvae. The seaweed-based diet also increased several long-chain fatty acids, such as stearic acid (C18:0), gondoic acid (C20:1 trans), eicosadienoic acid (C20:2), heneicosanoic acid (C21:0), and behenic acid (C22:0), whereas it decreased total polyunsaturated and n-6 fatty acids of larvae. The Firmicutes bacterial population decreased by ∼0.7% in the fed condition but increased by ∼27% in the fasted condition. In contrast, Proteobacteria were reduced in both fed (∼11 %) and fasted (∼29 %) conditions in the gut of YML exposed to the seaweed-based diet compared to the control diet. Furthermore, the inclusion of A. nodosum in the diet promoted specific beneficial bacterial species ( Lactobacillus coleohominis, Lactobacillus reuteri, and Lactobacillus salivarius ) while suppressing potentially pathogenic bacteria ( Alistipes onderdonkii and Bacteroides fragilis ) on YML gut. Our findings provide empirical evidence that the dietary inclusion of marine brown seaweeds can improve the nutritional values and the gut microbial communities of YML.

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