Arachidonic acid regulates hormonal crosstalk to promote molting success and mediate a life-history trade-off in a wolf spider

Abstract

The biochemical composition of prey is a critical factor shaping the life-history strategies of obligate predators, yet the molecular mechanisms through which specific nutrients regulate complex developmental processes remain largely unknown. Using the wolf spider Pardosa pseudoannulata as a model, where arachidonic acid (ARA) is indispensable for preventing molting death, we integrated life-history analysis and RNA sequencing to elucidate its regulatory role. We discovered a significant life-history trade-off: while essential for survival, dietary ARA significantly prolonged early instar duration. Transcriptomic analysis revealed that ARA orchestrates a two-phase developmental strategy to resolve this conflict. The “preparation” phase, marked by the upregulation of juvenile hormone synthesis (JHAMT), corresponds to the developmental delay and facilitates resource accumulation. This is followed by an “execution” phase, where ARA triggers the entire ecdysone cascade, from biosynthesis (e.g., Spook, Shade) and signaling (USP) to catabolism (CYP18A1). This hormonal activation was coupled with the substantial upregulation of downstream effector genes, including dozens of cuticular proteins. Our findings indicate that ARA acts as a key signaling molecule that coordinates the hormonal crosstalk between developmental timing and molting. This study provides a comprehensive molecular model for the nutritional regulation of arthropod development, linking nutrition, physiology, and survival.