Pardosa pseudoannulata mother adopts a compensatory strategy for reproduction deficiency resulting from the suppression of EcR/USP-1-mediated ecdysteroid signaling

Abstract

Spiders express specific maternal care to their offsprings. The predatory spider Pardosa pseudoannulata mother constructs an eggsac to protect her eggs and juvenile spiderlings. However, here we found that the female spiders ate their eggsacs when ecdysteroid signaling was suppressed. Nuclear receptors (NRs), especially ecdysone receptor (EcR) and ultraspiracle (USP), have attracted extensive attention in arthropods because of their pivotal roles in ecdysteroid signaling cascades. An EcR and two USPs were identified in P. pseudoannulata genome. RNAi against EcR and USP-1 restrained the development of spiderlings, such as delaying moulting and decreasing moulting rate. EcR- and USP-1-silenced adult females produced more invalid eggsacs full of nonviable eggs than the control counterpart, and they ate the invalid eggsacs. EcR and USP-1 responded to the changes of ecdysteroid, and CYP307A1 knockdown led to the similar phenotypes to dsEcR and dsUSP-1 treatments. It proposed that EcR/USP-1-mediated ecdysteroid signaling regulated the development and reproduction in P. pseudoannulata. The period of the first reproduction cycle was 17.87 d in the ecdysteroid signaling-suppressed females, which was 7.19 d shorter than that of the control (25.06 d). The result meant that, when the female spiders detected the nonviable eggs in eggsac, they forwardly ate the invalid eggsac to terminate the useless reproduction cycle and start a new cycle by generating a new eggsac. The strategy can partially compensate for the loss of population growth due to the nonviable eggs, and eating the invalid eggsac also provide a compensation for the physiological consumption during the invalid eggsac care.