Buprofezin delayed the molting of Pardosa pseudoannulata, a predatory enemy for insect pests, by suppressing chitin synthase 1 expression.

Spiders, the major predatory enemies of insect pests in fields, are vulnerable to insecticides. In this study, we observed that the recommended dose of buprofezin delayed the molting of the pond wolf spider Pardosa pseudoannulata, although it had no lethal effect on the spiders. Since buprofezin is an insect chitin biosynthesis inhibitor, we identified two chitin synthase genes (PpCHS1 and PpCHS2) in P. pseudoannulata. Tissue-specific expression profiling showed that PpCHS1 was most highly expressed in cuticle. In contrast, PpCHS2 showed highest mRNA levels in the midgut and fat body. RNAi knockdown of PpCHS1 significantly delayed the molting of 12-days old spiderlings, whereas no significant effect on the molting was observed in the PpCHS2-silencing spiderlings. The expression of PpCHS1 was significantly suppressed in the spiderlings treated with buprofezin, but rescued by exogenous ecdysteroid ponasterone A (PA). Consistent with this result, the molting delay caused by buprofezin was also rescued by PA. The results revealed that buprofezin delayed the molting of spiders by suppressing PpCHS1 expression, which will benefit the protection of P. pseudoannulate and related spider species.

m-Aminophenylacetylene induces maternal care in a predatory spider.

Maternal care is critically important for the survival of offspring in various animals. Spiders in the family Lycosidae are known for their hunting ability and maternal care behaviors. Predation on newly hatched spiderlings (pulli) by mother spiders decreases when they come into contact, and they carry the pulli on their dorsal surface. However, the factors inducing maternal care in lycosid spiders have not been elucidated. In this study, we investigated maternal care in Pardosa pseudoannulata (Araneae, Lycosidae) females. We proposed that the physical interaction between pulli and mother spiders induces maternal care via m-aminophenylacetylene (m-A), a novel regulator of maternal care. The presence of pulli on the dorsal abdomen of non-mother spiders suppressed pulli predation and increased the pulli-carrying rate, and the absence of pulli on the mother spiders increased pulli predation and decreased the pulli-carrying rate. The compound m-A was abundant in mother spiders, and it could be induced in non-mother spiders when they carried pulli. The topical application of m-A to non-mother spiders and m-A injection decreased pulli predation and increased the pulli-carrying rate, respectively; these findings indicate that m-A in both internal tissues and the integument is required for the induction of maternal care behavior, and the interaction between pulli and females induces the production of m-A. In-depth study of the regulatory mechanism of maternal care will enhance our understanding of spider biology and behavior.