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...

Micro-CT analysis reveals directional genital asymmetry in a mygalomorph spider with two different sperm-storage organs (Araneae: Mecicobothriidae)

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Micro-CT analysis reveals directional genital asymmetry in a mygalomorph spider with two different sperm-storage organs (Araneae: Mecicobothriidae)

Abstract

Sexual selection is a pervasive evolutionary force shaping the extraordinary diversity of animal genitalia, often driving rapid morphological divergence and complex interactions between male and female reproductive structures. In spiders, sexual selection acts through both pre- and postcopulatory mechanisms, frequently resulting in elaborate male intromittent organs, specialized female sperm-storage structures, and intricate mating behaviours. Despite this diversity, mygalomorph spiders have traditionally been regarded as morphologically conservative, with comparatively simple genitalia and stereotyped reproductive patterns. In this study, we provide the first integrative analysis of genital functional morphology, copulatory mechanics, and mating behaviour in a mygalomorph species, Mecicobothrium thorelli. Our results reveal a surprising degree of anatomical and behavioural complexity. Most notably, we document the first known instance of directional genital asymmetry in a mygalomorph spider. Female genitalia are characterized by two distinct spermathecal types, with one being asymmetric. This asymmetry is matched behaviourally by differential, selective use of the symmetric male copulatory organs. The consistent preference for specific male–female genitalia combinations suggests finely tuned mechanical and functional coordination during copulation. By uncovering these hidden complexities, our study expands current understanding of sexual selection and genital evolution in early-diverging spider lineages.

Panchuk, J., Ferretti, N., Poy, D., Ramírez, M., & Michalik, P. (2026). Micro-CT analysis reveals directional genital asymmetry in a mygalomorph spider with two different sperm-storage organs (Araneae: Mecicobothriidae). Zoological Journal of the Linnean Society, 207(2). https://doi.org/10.1093/zoolinnean/zlag075