Sexual Size Dimorphism in Buthus tunetanus (Scorpiones: Buthidae) from Tunisia

Abstract

Scorpions are known to exhibit sexual size dimorphism, but data is still lacking from a large number of species throughout the world. Such information is nonetheless essential for a better understanding of the factors and processes shaping scorpion morphology. In this work, we investigated sexual size dimorphism in Buthus tunetanus, a common scorpion species in Tunisia. Using morphometric data on a sample of 100 females and 142 males, we assessed sexual differences in body parts and investigated allometric relationships. Results showed significant sexual size dimorphism in weapon systems, namely the metasoma and chelae. More specifically, there was male-biased dimorphism in metasoma size but female-biased dimorphism in chela size. Increased body size was associated with an exaggerated increase in metasoma size in males and chela size in females. These patterns are in agreement with those previously reported in other scorpion species and highlight the roles of sexual differences in mating behavior and ecological requirements in shaping the morphology of weapon systems in scorpions.