Low intensity UVB irradiation increases expression of the toll pathway in the yellow mealworm Tenebrio molitor (Coleoptera: Tenebrionidae)

As the demand for sustainable protein grows, insect farming has emerged as a promising solution. The yellow mealworm ( Tenebrio molitor ), among other commercially farmed species, presents a variety of environmental and nutritional advantages to conventional livestock. However, mealworm colonies are vulnerable to pathogens, necessitating novel strategies for enhancing their immune resilience. This study used a transcriptomic approach to investigate the potential immunostimulatory effects of low-intensity ultraviolet B (UVB) irradiation on mealworm larvae. Mealworm larvae were exposed to UVB light for 14 days, followed by a fungal challenge ( Beauveria bassiana ). UVB irradiation did not significantly affect survival 14 days post-challenge but negatively impacted larval weight. Analysis of differential gene expression showed a notable increase in the activity of Toll pathway transcripts and the transcripts encoding three antimicrobial peptides (AMPs) immediately following UVB exposure. This research indicates that while UVB irradiation triggers AMP production in mealworms, this does not enhance resistance to the fungal pathogen Beauveria bassiana . These observations lay the groundwork for additional studies exploring UVB radiation’s effects on insect immune systems and its potential use in commercial insect rearing.