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Inbreeding sabotages rare species' sperm

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    Inbreeding sabotages rare species sperm * 00:01 04 March 2009 by Catherine Brahic * For similar stories, visit the Endangered Species and Genetics Topic
    Message 1 of 1 , Mar 4, 2009
       Inbreeding sabotages rare species' sperm

          * 00:01 04 March 2009 by Catherine Brahic
          * For similar stories, visit the Endangered Species and Genetics Topic Guides

      It's a triple whammy for male animals on the brink of extinction: not only are there fewer mates around to have sex with, but, to make things worse, their sperm are more likely to carry genetic abnormalities and less likely to be good swimmers, research shows.

      "It is logical that endangered species are inbred and suffer reductions in fitness, but we don't have a clear idea of what is the driving force behind this," says John Fitzpatrick of the Centre for Evolutionary Biology at the University of Western Australia in Perth.

      Fitzpatrick and colleague Jonathan Evans compared existing data on sperm fitness for 20 endangered and non-endangered species of mammals, including the Florida panther, Asiatic lion and cheetah. Scientists have previously observed extreme reductions in sperm quality for each of these big cats - all of which also suffered huge reductions in population size that led to inbreeding.

      The team found that, on average, 48% of the sperm of endangered species was abnormal, compared with 30% in non-endangered species. In addition, the percentage of the sperm that was motile - or capable of movement - was around 10% lower in endangered species. Earlier research has shown that both characteristics make a male less likely to produce viable offspring.
      Sperm bank hope

      For each species, the researchers also looked at how heterozygous, or diverse, their DNA was - an indication of how inbred the animals were. For non-endangered species, they found no relation between the characteristics of sperm and DNA. However, less diverse homozygous DNA correlated with reduced sperm fitness for endangered species.

      How inbreeding causes a decrease in sperm quality is unclear. Scientists believe inbreeding disrupts the complex mix of genes that is needed to produce "normal" sperm.

      "The most exciting part of our research is that it clearly shows that inbreeding impairs sperm quality," says Fitzpatrick. Importantly, he adds, the results also show endangered species that still have a significant amount of genetic diversity also have sperm comparable to non-endangered species.

      This offers a way of dampening the problem. Several conservation groups have advocated creating sperm banks of rapidly declining species. Such stores of frozen genetic diversity could increase the fertility of endangered animals, and help conservation biologists boost populations before they become critically endangered.

      Journal reference: Biology Letters (DOI: 10.1098/rsbl.2008.0734)

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