14 February, 2020

The role of sexual dimorphism in prey capture in two scorpion genera with different degree of male and female dimorphism

Sexual differences in morphology and other traits occur in many scorpion species, while the male and female are quite similar in others. In scorpions, sexual dimorphism is usually associated with mating and associated behavior.

Morphological differences in pedipalps and cauda have an impact in prey capture tactics, sting use and venom use in scorpions. Scorpions with large, powerful pedipalps will often not use their stinger and rely on the power of the pedipalps compared to species with more slender pedipalp.

Julio Cesar Gonzalez-Gomez and co-workers have recently published an article combining the above mentioned characteristics in scorpions by looking into the role of sexual dimorphism in prey capture in one group of scorpions with large sex differences and another group with minor differences. As espected they found significant differences between males and females in the group with large sexual dimorphism, and no differences in the group with minor differences.

Morphological differences between the sexes are a common feature in many groups of animals and can have important ecological implications for courtship, mating, access to prey and, in some cases, intersex niche partitioning. In this study, we evaluated the role of sexual dimorphism in the performance of the two structures that mediate the ability to access prey, the pinchers or chelae and the venomous stinger, in two species of scorpions with contrasting morphologies: Chactas sp., which has marked sexual dimorphism in the chelae, and Centruroides sp., which does not have such marked dimorphism in the chelae. We evaluated aspects such as chela pinch force, toxicity to prey (LD50) and the volume of venom in males and females of each species. We found significant differences between males and females of Chactas sp. in the chela pinch force, volume of venom and LD50. In contrast, for Centruroides sp., no differences between males and females were found in any of these traits. We discuss several potential selective regimes that could account for the pattern observed.

González-Gómez JC, Valenzuela-Rojas JC, García LF, Franco Pérez LM, Guevara G, Buitrago S, et al. Sexual dimorphism in the biomechanical and toxicological performance in prey incapacitation of two morphologically distinct scorpion species (Chactas sp. and Centruroides sp.). Biological Journal of the Linnean Society. 2020;129(1):190-8. [Subscription required for full text]

Thanks to Luis Fer for sending me this article!

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