THERE is such a thing as being too well-endowed – at least if you’re a cobweb spider. Male Tidarren sisyphoides boast such an enormous pair of copulatory organs that they amputate one to make moving around easier.
Male T. sisyphoides spiders weigh only about 1 per cent as much as females, and therein lies the problem: in order to fit together properly with the female during mating, the males have a pair of disproportionately huge copulatory organs, known as pedipalps. They account for roughly a fifth of the males’ total weight. Rather than lug these monstrosities around, each male tears one off shortly before adulthood.
This self-mutilation has great benefits. Margarita Ramos and her colleagues at Tulane University in New Orleans, Louisiana, tested 16 males and found they ran an average of 44 per cent faster shortly after losing a pedipalp than they did while still intact (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0400324101).
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The team suspects that the extra nimbleness helps males find a female and win the race to mate using their remaining organ.