ISSUE FOCUS 26 Alternative Proteins Magazine April 2025 CAN WE FEED FISH WITH PLASTIC-EATING INSECTS? A recent study explored whether plastic-degrading larvae could be used to feed fish intended for human consumption —contributing to a circular approach in aquaculture (Bonilla-Amaya et al., 2024). The trial tested diets for juvenile red-bellied pacu (Piaractus brachypomus), replacing fishmeal with insect meal made from T. and Z. atratus fed a mixture of 25% PS and 75% wheat bran. The results were promising. This combination not only promoted greater PS degradation —up to 65% in 64 days for T. molitor and 12% in 32 days for Z. atratus— but also yielded insect meals with high protein content: 51% for T. molitor and 42.6% for Z. atratus, comparable to values reported for conventionally reared insects. Fish fed with these insect-based meals grew normally, with no differences in development observed. The authors concluded that up to 100% of fishmeal could be replaced by insect meal from larvae reared on PS, without compromising performance or apparent health. However, they also emphasized the need for further safety evaluations, particularly regarding the potential accumulation of microplastics or toxic residues in the insect biomass. ENSURING THE SAFETY OF LARVAE FOR FEED During degradation, plastics break down into increasingly smaller particles, including micro- and nanoplastics, raising concerns about the potential accumulation of toxic compounds in the larvae or their transformation into harmful substances. In in vitro cellular analyses, extracts from Tenebrio molitor and Zophobas morio larvae fed with EPS did not show cytotoxic effects (Zielińska et al., 2021). No adverse impact on the intestinal health of the larvae was observed either. Still, more evidence is needed to confirm that these insects pose no health risks when used in feed. Ensuring safety —for the larvae and for the end consumers— remains a critical priority in the development of this technology. A recent study concluded that up to 100% of the fishmeal could be replaced in the diet of juvenile red-bellied pacu with meal from larvae fed polystyrene, although further studies are needed to assess the possible presence of toxins Studies show that Tenebrio molitor can convert up to 48% of expanded polystyrene carbon into CO2 within 16 days, with another 49% excreted as frass
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