Low Intensity UVB as an Immunostimulant in the Yellow Mealworm Tenebrio molitor (Coleoptera: Tenebrionidae)

Abstract

As the demand for sustainable proteins 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 over conventional livestock. However, mealworm colonies are vulnerable to pathogens, necessitating novel strategies for enhancing their immune resilience. Here, we employed a transcriptomic approach to investigate the immunostimulatory effects of low-intensity ultraviolet B (UVB) irradiation on mealworm larvae. Approximately 3-week-old mealworms were exposed to UVB light for 14 days, followed by fungal challenge (Beauveria bassiana). UVB irradiation did not confer significant differences in survival at 14 days post-challenge and had a negative effect on larval weight. Genome-wide differential gene expression analysis revealed significant dysregulation of Toll pathway transcripts, including those encoding three antimicrobial peptides (AMPs), immediately after UVB exposure. Targeted gene expression analysis validated the upregulation of tenecin 4 via a response in the fat body at one and 14 days after the initiation of UVB irradiation. This study indicates that while UVB irradiation positively modulates AMP production in mealworms, its impact on enhancing resistance to pathogens remains uncertain. These observations lay the groundwork for additional studies exploring the effects of UVB irradiation on insect immune systems and its potential implications for insect farming.