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Virgin Births In Sawfish No Divine Intervention: Here's The Science Behind It

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Wildlife experts have started investigating how a small group of smalltooth sawfish in Florida was able to reproduce in the wild without the need of a partner.

In a recent study published in the journal Current Biology, scientists from the Stony Brook University in New York and the Field Museum of Natural History in Chicago discovered seven sawfish in an estuary that were able to engage in asexual reproduction.

This type of reproduction is commonly seen among animals without backbones called invertebrates. Virgin births in vertebrates, however, are known to be extremely rare and those that were observed mostly happened among animals in captivity.

One example is a Komodo dragon at the Chester Zoo in London that was able to conceive eight offspring through asexual reproduction.

Scientists recently found two female snakes in the wild that were impregnated through parthenogenesis, but they were unsure whether or not the offspring of these snakes would have survived in their environment. This is why virgin births in animals outside of captivity have yet to be studied fully by wildlife experts.

"Vertebrate animals that we always thought were restricted to reproducing via sex in the wild actually have another option that does not involve sex," co-author Demian Chapman from the Stony Brook University said.

"Rare species, like those that are endangered or colonizing a new habitat, may be the ones that are doing it most often. Life finds a way."

The authors of the study conducted a DNA fingerprinting of the smalltooth sawfish they recovered in order to find out if they had mated with relatives due to their relatively small population.

Andrew Fields, the lead researcher, said they found evidence pointing to the inherent ability of female sawfish to reproduce even without mating. This process is called parthenogenesis.

In parthenogenesis, an egg cell is created by dividing a singular precursor cell into four separate ones. The cell that develops into an egg cell retains the cytoplasm and other vital cellular structures. The remaining three contain excess genetic material.

Fertilization happens when one of the three extra cells essentially turns into a sperm cell and combines with the egg cell. The resulting egg cell contains about half of the genetic diversity of its mother. This trait is also what allows scientists to identify parthenogenesis through genetic testing.

"It really surprised us," co-author Kevin Feldheim, from the Chicago Field Museum's Pritzker Laboratory for Molecular Systematics and Evolution, said.

"It is possible that numbers are so low that females have a hard time finding mates. In such a situation, parthenogenesis can be used as a last-ditch effort for a female to pass on her genes."

The population of sawfish saw a significant decrease in the past few years due to the continued loss of their natural habitat. They are also threatened by "unintentional" over-fishing wherein they get caught in nets intended for other fish species.

In 2003, they were included in the list of endangered species protected under U.S. federal law.

While the findings of their study identified parthenogenesis among smalltooth sawfish, the researchers cautioned that the process alone will not be enough to save their dwindling numbers.

"It would be great to use this interesting finding to inspire conservation action for sawfish," Chapman added.

The Stony Brook University and Chicago Field Museum study is featured in Current Biology.

Photo: Guy Incogneato | Flickr

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