Sexual dimorphism in the scorpions of the genus Odontobuthus Vachon, 1950 (Scorpiones: Buthidae)

Abstract

The Sexual dimorphism (SD) in body size is very common among the scorpions. In this study, the SD was investigated in two aspects of size and shape in the genus Odontobuthus Vachon, 1950 as a small genus of the family Buthidae. This genus has six fossorial species of which four are distributed in Iran. For this purpose, 43 morphometric variables, consisting of 38 metric measurements and five meristic characters were digitized in the six species, O. bidentatus, O. doriae, O. tavighiae, O. tirgari, O. sp.1 and O. sp.2. The results show that Sexual Size Dimorphism (SSD) were significant in three species:  O. doriae, O. tavighiae and O. sp.2. While O. sp.1 represented a SD for more aspects of shape, O. bidentatus did not show a significant SD for all studied traits. The amount of SD in size and shape were not the same in different species. The results showed that males have larger metasoma than females even when they are pulled to the same size. Having larger metasoma may correspond to a more efficient performance during mating, predation or combat with other males, so it should be under a high sexual selection. Type II ANOVA showed a significant interaction between species and sex for shape, but not for size. It suggests that the evolution of SD for size has been in parallel for all studied species, while it has been in different directions for shape. Among meristic variables, only the number of pectin denticles were sexually dimorphic, with males having more denticles than females in all studied species.