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Social structure predicts genital morphology in African mole-rats
Marianne L Seney1, Diane A Kelly, Bruce D Goldman
1Center for Neuroendocrine Studies and Department of Psychology, University of Massachusetts, Amherst, MA, USA. marianne.seney@gmail.com
Plos One
|October 16, 2009
Summary
African mole-rat social structures influence sexual differentiation. The eusocial naked mole-rat lacks genital sex differences, unlike solitary species, suggesting evolution tied to social behavior.
Area of Science:
- Comparative anatomy
- Evolutionary biology
- Mammalian reproductive systems
Background:
- African mole-rats (Bathyergidae, Rodentia) display diverse social systems, from solitary to eusocial.
- The eusocial naked mole-rat uniquely lacks sex differences in external genitalia and associated perineal muscles, contrasting with other mammals.
- This lack of dimorphism in naked mole-rats was hypothesized to be linked to their distinct social structure.
Purpose of the Study:
- To investigate the relationship between social structure, mating systems, and sexual differentiation in African mole-rats.
- To compare genital and perineal muscle morphology across different social structures within the Bathyergidae family.
Main Methods:
- Comparative morphological analysis of genitalia and perineal muscles.
- Examination of three mole-rat species: naked mole-rat (eusocial), silvery mole-rat (solitary), and Damaraland mole-rat (eusocial with less reproductive skew).
Main Results:
- Naked mole-rats exhibit no significant sex differences in genital and perineal morphology.
- Silvery mole-rats display clear sexual dimorphism in these anatomical features.
- Damaraland mole-rats present an intermediate level of sexual differentiation, correlating with their social structure.
Conclusions:
- The absence of sexual differentiation in naked mole-rats is specific to their species and not a general trait of African mole-rats.
- Evolutionary pressures related to their unique social organization and reproductive biology likely drove the loss of genital sexual dimorphism.
- Findings support a strong link between social complexity, mating systems, and the evolution of reproductive anatomy in mammals.
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