EcR/USP-1-mediated ecdysteroid signaling regulates wolf spider (<i>Pardosa pseudoannulata</i>) development and reproduction

Lycosidae females demonstrate meticulous maternal care of offspring by carrying egg sacs and juvenile spiderlings during the reproductive stage. Nuclear receptors (NRs), especially the ecdysone receptor (EcR) and ultraspiracle (USP), have attracted considerable attention in the regulation of arthropod development and reproduction due to their pivotal roles in ecdysteroid signaling cascades. In the present study, 23 NRs, including one EcR and two USPs, were identified in the genome of the predatory wolf spider Pardosa pseudoannulata. RNA interference (RNAi) targeting EcR and USP-1 inhibited spiderling development and resulted in non-viable eggs in the egg sacs. EcR and USP-1 responded to changes in ecdysteroid levels, and interference in ecdysteroid biosynthesis led to similar phenotypes as dsEcR and dsUSP-1 treatments. These findings suggest that EcR/USP-1-mediated ecdysteroid signaling regulates P. pseudoannulata development and reproduction. The P. pseudoannulata females with suppressed ecdysteroid signaling proactively consumed their non-viable egg sacs, resulting in a 7.19 d shorter first reproductive cycle than the controls. Termination of the failed reproductive cycle enabled the spiders to produce a new egg sac more rapidly. This reproductive strategy may partially rescue the reduction in population growth due to non-viable eggs and compensate for the physiological expenditure of wasted maternal care, which would be beneficial for the conservation of P. pseudoannulata populations and their natural control of insect pests.