Beneath the surface: A new northern species of Trogloraptor (Araneae: Trogloraptoridae), genetic diversity and natural history

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  Beneath the surface: A new northern species of Trogloraptor (Araneae: Trogloraptoridae), genetic diversity and natural history Abstract We present a morphological description of a recently discovered species of spider in the family Trogloraptoridae from the Columbia River Gorge in northwestern Oregon. The family was previously monotypic (Trogloraptor marchingtoni) and only known from populations near the southwestern Oregon—northern California border. Trogloraptor tulishpun sp. nov. retains the key family synapomorphy, distinctive subsegmented raptorial tarsi, and an oblique membranous division of the basal segment of the anterior lateral spinnerets. Trogloraptor tulishpun is distinguished from T. marchingtoni by its color pattern, clypeal height, vulvar and palp structure. We have found T. tulishpun in four localities in the Columbia River Gorge, which show little mitochondrial sequence divergence from one another, but are highly genetically distinct from T. marchingtoni. Troglo...

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