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Male pond skaters forced to 'sing' for sex

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    Male pond skaters forced to sing for sex Synopsis below: Full article and movie at: http://www.newscientist.com/article/
    Message 1 of 1 , Jun 14, 2009
      Male pond skaters forced to 'sing' for sex

      Synopsis below:

          * 14:33 12 June 2009 by Andy Coghlan
          * For similar stories, visit the Evolution and Love and Sex Topic Guides

      Video: See the serenading skaters


      By evolving a "shield" for their genitals, female pond skaters can decide for themselves whether to allow males to mate with them.

      They decide whether or not to mate by listening to "songs" made when male suitors use the tips of their long mid-legs to tap out rippling rhythms on the water surface.

      In other pond skater species – also known as water striders – males run the show, mating with females almost at will because they have no means to resist. Nor is there usually any form of courtship.

      But the red-backed water strider, found in stationary pools beside mountain streams in Korea, Japan and China, has now proved to be the exception. Detailed experiments and anatomical analyses have now shown that females of Gerris gracilicornis have evolved a protective shield for their genitalia.

      Moreover, they will only lift the shield if males go through an elaborate mating ritual lasting about 15 minutes, in which they use the tips of their mid-legs to tap out the intricate rhythms.

      "In this species, the female is in control because she normally keeps her genitalia hidden behind a shield of the last abdominal segment," says Han. "Only when the female expands and protrudes her genitalia from behind this shield can the male have access for mating."

      To win their prize, courting red-backed strider males must tap out three consecutive songs. Firstly, the males grip the female from behind and manoeuvre her into the mating position with their forelegs. During this ritual, they extend their long mid-legs forwards and begin tapping rhythms – dubbed "grasping signals" – on the water.

      Next come the "mounting signals", during which the male engages his own genitalia with the partially exposed genitalia of the female.

      Finally come the most regular bouts of tapping, when the female finally yields and lifts the shield, exposing her ovipositor and allowing full mating to occur.

      One possibility is that the quality of the rhythm reveals the fitness of the male, enabling the female to mate only with the best available. It may be that the female has internal anatomy that enables her to accept or reject the sperm after mating, and the serenading helps her decide which choice to make.

      Journal reference: PLoS One (DOI: 10.1371/journal.pone.0005793)

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