Optimal ultra-short copulation duration in a sexually cannibalistic spider

Limitations of sperm transfer in the complex reproductive system of spiders

In spiders, sperm transfer from the male to the female is indirect via secondary copulatory structures, the pedipalps. At the time of transfer the sperm are not mobile and the ejaculate needs to move through narrow male and female ducts to the female sperm storage organ. In addition, copulation duration can be very short, often limited to just a few seconds. Finally, sexual cannibalism and genital damage limits male life-time mating opportunities. These features of the reproductive biology in spiders are likely to result in sperm transfer constraints. Here we review the intrinsic and extrinsic sperm transfer limitations and conduct a meta-analysis on sperm transfer data from published data. Most of the information available relates to orb-web spiders, but our meta-analysis also includes non-orb-web spiders. Our review identifies some of the behavioural factors that have been shown to influence sperm transfer, and lists several morphological and physiological traits where we do not yet know how they might affect sperm transfer.

Female control of a novel form of cannibalism during copulation in a South American widow spider

Sexual cannibalism is an extreme form of sexual conflict that may have broad evolutionary effects on mating behaviour. Latrodectus spiders (∼30 "widow" species) could enable comparative tests of the evolution of sexual cannibalism, but most species are poorly-studied. Here we describe the mating and remating behaviour of a species endemic to South America, L. mirabilis, with a focus on the occurrence and consequences of sexual cannibalism. Mating and cannibalistic behaviours were novel relative to other Latrodectus species. Cannibalism started during copulation when females grasped the male's legs with their chelicerae, and continued as females pulled the male's abdomen onto their chelicerae, without interrupting copulation. Cannibalism was initiated by females, and not facilitated by males as was observed in other Latrodectus species. Females frequently remated however, so cannibalized males might lose paternity to future rivals. We report high rates of cannibalism, with 70 % of males killed by females during their first mating, and 85 % killed by previously-mated females. We discuss our novel findings in the context of previous observations in other Latrodectus species, proposing that foundational studies in a wider range of species are necessary to support comparative tests about the evolution of sexual cannibalism within this model taxon.