Nutritional deficiency suppresses reproduction in Serangium japonicum through vitellogenin down‐regulation

BACKGROUND: Serangium japonicum is a key predator for whitefly biological control; however, mass rearing using alternative prey such as Ephestia kuehniella eggs may compromise its effectiveness. Although alternative prey are essential for cost-effective production, their nutritional adequacy for maintaining reproductive performance remains poorly understood. This study aimed to elucidate how nutritional quality affects S. japonicum reproduction using integrated biological, developmental, and molecular approaches. RESULTS: Alternative prey drastically reduced reproductive output by > 98% compared with natural prey, with only 40% of females successfully ovipositing. Ovarian development analysis revealed a 20-day delay in mature egg formation and severely compromised vitellogenesis. Adult prey-switching experiments demonstrated that nutritional deficiency effects were reversible: females switched from poor to high-quality prey and rapidly resumed reproduction within 24 h, while the reverse switch immediately ceased oviposition. Transcriptomic analysis identified 1229 differentially expressed genes, with 32 significantly down-regulated reproduction-related genes. RNA interference targeting vitellogenin genes SjVg1 and SjVg2 confirmed their essential roles, with gene silencing replicating the reproductive decline observed under poor-quality feeding. Notably, larvae fed alternative prey followed by adults fed natural prey showed 1.8-fold higher fecundity than the controls, suggesting adaptive nutritional compensation. CONCLUSION: These findings highlight how nutritional stress impairs predator performance and identify molecular targets for designing optimized artificial diets that sustain the biocontrol efficacy of S. japonicum. © 2026 Society of Chemical Industry.