Remarkable micro-endemism and high congeneric richness: eight new cave-restricted species of Pseudochthonius Balzan, 1892 (Pseudoscorpiones, Chthoniidae) from the Brazilian semi-arid

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  Remarkable micro-endemism and high congeneric richness: eight new cave-restricted species of Pseudochthonius Balzan, 1892 (Pseudoscorpiones, Chthoniidae) from the Brazilian semi-arid Abstract Eight new species of pseudoscorpions belonging to the genus Pseudochthonius Balzan, 1892 are described from the semi-arid region of Brazil. Comprehensive morphological descriptions, diagnostic characters, detailed illustrations, and ecological remarks of the habitats are provided for Pseudochthonius celestialis sp. nov., P. caritas sp. nov., P. patientia sp. nov., P. temperantia sp. nov., P. diligentia sp. nov., P. castitas sp. nov., P. humilitas sp. nov., and P. benignitas sp. nov. In addition, we present a brief discussion of the potential factors underlying the remarkable congeneric species richness observed in this geographically restricted region, as well as the principal threats faced by these species. These findings underscore the importance of conserving caves in order to pr...

The Halloween gene shadow is involved in embryonic development and postembryonic molting in the spider Parasteatoda tepidariorum

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The Halloween gene shadow is involved in embryonic development and postembryonic molting in the spider Parasteatoda tepidariorum

Abstract

Ecdysteroids are key hormones that regulate molting and developmental processes in arthropods, including insect metamorphosis. Understanding the molecular roles of the genes involved in ecdysteroid biosynthesis could provide crucial insights into the evolutionary conservation of regulation and regulatory modifications in arthropods. While extensively studied in insects, the functions of the so-called Halloween genes, encoding enzymes responsible for the conversion of cholesterol to ecdysone and 20-hydroxyecdysone, remain unclear in arachnids. Therefore, this study aims to elucidate the functions of the Halloween gene shadow (Pt-sad) in the spider Parasteatoda tepidariorum in both embryonic and postembryonic stages and to assess its potential role in molting. In situ hybridization was employed to characterize the expression patterns of Pt-sad, and RNAi-mediated knockdown (RNA interference) was conducted to explore its effects on development and molting. Knockdown of Pt-sad resulted in increased embryonic mortality and developmental delays, while it disrupted molt cycles in the postembryonic stages, supporting a role in ecdysteroidogenesis. Expression analysis revealed Pt-sad activity in specific regions of embryos and juveniles, including the central nervous system, appendages, and circulatory system. These findings highlight the multifunctionality of shadow in the spider. While the involvement of this gene in the ecdysteroid pathway is most likely conserved in arthropods, this role may have diversified in spiders to include additional, unique functions that differ from their insect counterparts.
Klinkenbuß, D., Treffkorn, S., Mayer, G., & Prpic, N. (2026). The Halloween gene shadow is involved in embryonic development and postembryonic molting in the spider Parasteatoda tepidariorum. Developmental Biology. https://doi.org/10.1016/j.ydbio.2026.02.010