Sexual dimorphism in jump kinematics and choreography in peacock spiders.

Abstract

Jumping requires a rapid release of energy to propel an animal. Terrestrial animals achieve this by relying on the power generated by muscles, or by storing and rapidly releasing elastic energy. Jumping spiders are distinctive in using a combination of hydraulic pressure and muscular action to propel their jumps. Though males and females of jumping spiders vary in body mass, sex-specific differences in jumping have never been studied. Here, we investigated the sexual dimorphism in the jump choreography and kinematics of spiders. We used high-speed videography (5000 frames s-1) to record locomotory jumps of males and females of the Australian splendid peacock spider, Maratus splendens. Using micro-computed tomography (µCT) imaging, we identified the animals' centre of mass and tracked its displacement throughout the jump. Our study revealed that peacock spiders exhibited the fastest acceleration among all known jumping spiders. Males demonstrated significantly shorter take-off times and steeper jump take-off angles compared with females. Our findings suggest that the third pair of legs acts as the propulsive leg in both male and female spiders. As males of M. splendens use leg III as part of the courtship display, we discuss the extreme selection pressure on this leg that drives two significant functions.