Copulatory mechanics in the wolf spider Agalenocosa pirity reveals a hidden diversity of locking systems in Lycosidae (Araneae). (30th December 2019)

• Record Type: Journal Article
• Authors: Poy, Dante; Ramírez, Martín J.; Michalik, Peter; Piacentini, Luis N.
• Is Part Of: Journal of morphology. Volume 281:Number 2(2020)
• Page Start: 250
• Page End: 257
• Publication Date: 2019-12-30
• Subjects: cryofixation -- genital mechanics -- micro‐CT; Morphology -- Periodicals; Physiology -- Periodicals; Anatomy -- Periodicals; 571.3
• DOI: 10.1002/jmor.21095
• Languages: English
• ISSNs: 0362-2525

Abstract

Abstract: Genital traits are among the fastest to evolve, and the processes that drive their evolution are intensively studied. Spiders are characterized by complex genitalia, but the functional role of the different structures during genital coupling is largely unknown. Members of one of the largest spider groups, the retrolateral tibial apophysis (RTA) clade, are characterized by a RTA on the male palp, which is thought to play a crucial role during genital coupling. However, the RTA was lost in several families including the species‐rich wolf spiders (Lycosidae) leading to the hypothesis that the genital coupling is achieved by alternative mechanisms. Here, we investigate the genital interactions during copulation in the wolf spider Agalenocosa pirity (Zoicinae) on cryofixed mating pairs using electron, optical and X‐ray microscopy and compare our findings with other lycosids and entelegyne spiders. We found an unprecedented coupling mechanism for lycosid spiders involving the palea and a membranous cuticle folding adjacent to the epigynal plate. Additionally, we show an uncommon coupling between the median apophysis and the contralateral genital opening, and confirmed that the terminal apophysis acts as functional conductor, as previously hypothesized for males of Zoicinae. Phylogenetic mapping of RTA indicated that the basal tibial process found in Agalenocosa is a secondary acquisition rather than a modified RTA. Abstract : Volume renderings of cryofixed coupled genitals of Agalenocosa pirity, all right male palps: a anterior view, showing the entire male palp position, the BTP would be normally in contact with the SA, b lateral view, c detail of lateral view; d ventral view, e anterior view. Abbreviations: BH, basal hematodocha; BTP, basal tibial process; Cy, cymbium; ED, embolic division; EF, epigastric furrow; DH, distal hematodocha; EP, epigynal plate; MA, median apophysis; SA, spiracle area; T, tegulum; Ti, tibia.