Comparison of chela size and pincer force in scorpions; getting a first grip

A key feature of the ancient body plan of scorpions is the pincer or chela. These multifunctional structures vary considerably in size and shape between different scorpion species. Here we provide the first comparative data on the pinching performance of the chelae of seven species of scorpions exemplifying the extremes of the shape range from slender to robust; Leiurus quinquestriatus, Androctonus amoreuxi, Androctonus australis, Hadogenes sp., Pandinus imperator, Scorpio maurus and Pandinus cavimanus (in the order of decreasing chela height to width ratio). Size-corrected chela height correlates highly with maximum pinch force. Independent contrasts suggest that the correlation of chela width, height and fixed finger length with maximum pinch force is independent of phylogeny, suggesting an adaptive component to the evolution of chela shape and performance.