August 5, 2012
Mating Plugs Produced By Female Spiders To Prevent Unwanted Sex From Males
redOrbit Staff & Wire Reports - Your Universe Online
A new mechanism of animal mating plug production has been discovered by scientists at the Smithsonian and their colleagues. In the giant wood spider (Nephila pilipes), which is a highly sexually dimorphic and polygamous species, many small males will compete with each other for their chance with a few large females. These males have been known to sever their own genitals during mating in order to plug the female, gain paternity and prevent other males form mating with her.
Researchers have also observed additional, very solid plugs commonly covering female genitals in this species. Biologists have recently discovered the origin of this additional other plugging mechanism.
The international team consists of MatjaÅ¾ Kuntner, research associate at the Smithsonian's National Museum of Natural History and chair of the Institute of Biology at the Scientific Research Centre, Slovenian Academy of Sciences and Arts; Daiqin Li, associate professor at the Department of Biological Sciences, National University of Singapore, and doctoral students MatjaÅ¾ Gregoric and Shichang Zhang, and postdoc Simona Kralj-FiÅ¡er. Their findings are published in the July 19 issue of the journal PLoS ONE.
Before the trials the researchers thought that the additional mystery plugs commonly found covering female genitals might be produced by the copulating male, or the female, or perhaps both sexes of the spider. By staging laboratory mating trials with varying degrees of females mating with multiple males, the researchers tested these possibilities. They found that no plugs were ever formed during the mating trials, but the females exposed to many males produced the amorphous plugs during the egg-laying process instead.
When hardened, these plugs prevented subsequent mating. The newly discovered "self-plugging" mechanism represents a female adaptation to sexual conflict through the prevention of unwanted and excessive copulations, the authors concluded.