Sawfish resort to virgin births to dodge extinction

Sawfish resort to virgin births to dodge extinction


Female sawfish can reproduce without fertilisation by a male, the first so-called “virgin births” to be observed in wild vertebrates.

Routine DNA analysis revealed that around three percent of the sawfish population living in a Florida estuary were born through asexual reproduction. Marine researchers behind the discovery said it had the potential to “rewrite the biology textbook”.

The process, also known as parthenogenesis, is common in invertebrates but rarely seen in vertebrates. It has previously been observed in birds, reptiles, and sharks in captivity, but not in the wild.

Researchers from New York’s Stony Brook University had been examining the sawfish to see if they had resorted to inbreeding due to their small population size, but what they found shocked them.

“What the DNA fingerprints told us was altogether more surprising; female sawfish are sometimes reproducing without even mating,” said Andrew Fields from the university’s School of Marine and Atmospheric Science.

The smalltooth sawfish, a type of ray that lives in southern Florida, was a common sight in the Atlantic less than a century ago, but is now an endangered species. The scientists behind the discovery have speculated that as sawfish are so now rare, females might not always find a male during mating season, forcing them to reproduce asexually.

“It is possible that parthenogenesis is most often expressed in wild vertebrates when the population is at very low levels and the animals have difficulty finding one another,” Fields said.

Parthenogenesis is triggered when an unfertilised egg combines with a cell called a polar body, which is almost genetically identical to the egg. This results in offspring that are a half clone of their mother. The study was published in the journal Current Biology.


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It had been though that parthenogenesis did not create viable offspring with the genetic similarities causing offspring to be malformed or die early. Asexual reproduction has been observed in some smaller animals in captivity, but its discovery in a large, wild vertebrate is a first.

“The seven parthenogens we found looked to be in perfect health and were normal size for their age. This suggests parthenogenesis is not a reproductive dead end, assuming they grow to maturity and reproduce,” said Dr. Gregg Poulakis of the Florida Fish and Wildlife Conservation Commission, who led the research.

The researchers have tagged the sawfish to monitor their development and have encouraged others carrying out similar work to screen their DNA databases to see if there are parthenogens hiding in other wild populations.

One comment

  • theunhivedmind

    We should note that this is based in Florida and that region was hit by the Corexit and oil pollutions tied to Deepwater Horizon.

    .·´ ¸.·★¨) ¸.·☆¨)
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    `·-☆ The Unhived Mind

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