Bioactive Substance Derived from Mealworm Larvae (Tenebrio molitor) Potentially Induces Immune Performance of Zebrafish (Danio rerio)

Mealworm (Tenebrio molitor) larvae meal is a notable alternative protein source that is widely used in the aquaculture industry. Recently, it has also gained recognition for enhancing the immune performance of various aquaculture species. However, stud ies identifying the specific bioactive substances responsible for the immunomodulatory effects of mealworm larvae meal remain limited. In this study, we isolated and purified a bioactive substance from mealworm and incorporated it into zebrafish (Danio rerio) diets at concentrations of 0, 10, and 100 µg/g; the zebrafish were fed this diet for 14 days. To assess the transcriptional changes induced by the bioactive substance, we performed RNA sequencing and qRT-PCR analysis on intestinal and liver tissues. Subsequently, zebrafish were challenged with Edwardsiella tarda via immersion in order to evaluate the protective effects of the bioactive substance. The results demonstrated that a dietary inclusion of 100 µg/g of the bioactive substance optimized the immune performance of zebrafish. Ad ditionally, challenge tests revealed that the dietary inclusion of the bioactive substance from mealworms positively influenced pathogen resistance, although these effects were not consistently significant