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Emasculation: gloves-off strategy enhances eunuch spider endurance.
Qi Qi Lee1, Joelyn Oh, Simona Kralj-Fiser
1Department of Biological Sciences, National University of Singapore, Singapore.
Biology Letters
|June 15, 2012
Summary
In sexually cannibalistic spiders, male genital mutilation (emasculation) enhances fighting endurance. This study confirms the
Area of Science:
- Evolutionary biology
- Animal behavior
- Sexual selection
Background:
- Sexual cannibalism is common in some spider species, leading to male genital mutilation (emasculation).
- Emasculated male spiders, known as eunuchs, exhibit superior fighting abilities when guarding mated females.
- The 'gloves-off' hypothesis suggests reduced body weight from emasculation enhances male endurance, but this remains untested.
Purpose of the Study:
- To test the 'gloves-off' hypothesis in the orb-web spider Nephilengys malabarensis.
- To investigate the relationship between genital mutilation and male locomotor endurance.
Main Methods:
- Experimentally created half-eunuchs (one palp removed) and full-eunuchs (both palps removed).
- Compared the time until exhaustion (endurance) of intact males with experimentally emasculated males.
- Measured body weight reduction due to emasculation.
Main Results:
- Emasculation reduced body weight by up to 4% in half-eunuchs and 9% in full-eunuchs.
- Endurance significantly increased by 32% in half-eunuchs and 80% in full-eunuchs.
- Results support the 'gloves-off' hypothesis.
Conclusions:
- Male emasculation in Nephilengys malabarensis enhances locomotor endurance.
- Reduced body weight from genital mutilation is a key factor in increased endurance.
- Male emasculation appears to be an adaptive strategy in this species.
