Mating behavior of the Sydney funnel-web spider (Atracidae: Atrax robustus) and implications for the evolution of courtship in mygalomorph spiders

Spiders have become a model group for sexual selection and mating system studies, but our understanding of courtship behavior in the group is heavily biased towards the infraorder Araneomorphae ('modern' spiders, such as orb weavers, jumping spiders, wolf spiders, crab spiders and many more). In the Mygalomorphae (tarantulas, trapdoor spiders, funnel-web spiders and relatives), only a few descriptions of courtship are available and recent developments in the phylogenetics of the group offer an opportunity to remap and investigate the evolution of mating behaviors. Using 81 trials filmed in captivity, we report on the courtship behaviors of the iconic Sydney funnel-web spider (Atracidae: Atrax robustus), which belongs to a large clade of biologically understudied mygalomorphs. Thirteen distinct behaviors are described for males, out of which at least two seem new to mygalomorphs, while four female behaviors are described. Moreover, the sequences of male behaviors are presented for when they come into contact with females inside or outside of their burrows. The mating positions of the pair, including details of how males use their legs and clasping spurs to grasp the females, are also presented. We discuss our results in a modern phylogenetic context, filling a gap in the understanding of sexual selection in the Mygalomorphae where such studies are rare and biased towards tarantulas. Finally, we attempt to consolidate descriptions of potentially homologous behaviors from several families in the group and offer insights into the evolution of cannibalism, male clasping spurs and female catalepsis (quiescence while mating).

Automated summary

Spiders, especially Araneomorphae, have been extensively studied for their courtship behaviors, while the understanding of courtship in Mygalomorphae is limited. This study focuses on the courtship behaviors of a mygalomorph, the Sydney funnel-web spider, and describes new behaviors not previously observed in this group. The mating positions and behaviors of males and females are also detailed. The research provides valuable insights into the evolutionary aspects of sexual selection in Mygalomorphae, which has been understudied and biased towards tarantulas.