What is behind the plug: determinants of an inter-sexual mating plug in a scorpion

OVIEDO DIEGO, MARIELA; MATTONI, CAMILO; HEBETS, EILEEN; PERETTI, ALFREDO

Montevideo

Congreso; 22nd International Congress of Arachnology; 2023

Males evolved strategies to reduce sperm competition, like mating plugs that block female genitalia and hinder remating. Both sexes might participate in plug formation so that sexual interests could determine its efficacy. In scorpions, the determinants of plug efficacy have not yet been studied. We analyzed whether the body condition or courtship behaviors could impact plug traits in Urophonius achalensis (Bothriuridae). This species has an inter-sexual plug formed by portions of spermatophore and hardening by female immune response triggering. We recorded matings (n=16) to quantify courtship behaviors: female resistance, male gland rubbing, and sexual sting. We then photographed the plug (visible externally) every three days (for one month) to analyze size increment and darkening (linked to hardening) with an image analysis software. We related plug traits to sexes’ body condition (residual index) and their courtship behaviors using GLMs in R. We found that higher-condition males transferred larger plugs, and higher-condition females had hardened plugs (stronger immune response). Longer female resistance during courtship was related to less hardened plugs, while longer male sexual sting to the female was linked to hardened plugs. Female resistance could signal partial rejection of certain males, which, related to less-hardened plugs (less efficacy), could facilitate female remating. These results show that multiple factors influence plug traits suggesting interest-dependent post-copulatory mechanisms of both sexes. Our findings offer new avenues to study cryptic female choice through the modulation of the immune response in an original study model contributing significantly to this area of sexual selection.