Sawfish Virgin Births—Nature’s Hail Mary

Scientists have discovered that smalltooth sawfish can reproduce without sex. But can parthenogenesis save the species?

June 10, 2015

Photo: Forrest Samuels via USFWS/Flickr

Lots of animals do it, and by “do it,” I mean not do it. Scorpions, bees, fleas, and even captive Komodo dragons have been known to reproduce asexually. In these cases, an unfertilized egg develops into offspring without being fertilized by a daddy. Scientists call it parthenogenesis, and scientists have, for the first time, discovered it happening within a vertebrate population in the wild.

And the animal that performs this real-life virgin birth? The already amazing smalltooth sawfish (Pristis pectinata).

As its name suggests, the smalltooth sawfish has a saw hanging off the end of its face. The animals use this bizarre accoutrement to sense and then slash at prey like something out of The Life Aquatic with Steve Zissou. As one of the biggest fish in the ocean, this elasmobranch is capable of growing up to 25 feet long and weighing almost 800 pounds. And though it looks like an off-brand knockoff of the hammerhead shark, the smalltooth sawfish is actually a type of ray.

The International Union for the Conservation of Nature lists smalltooth sawfish as critically endangered. There may be as many as 5,000 adults left in the world—or as few as 200. And pretty much all of them live in Florida. Given how few sawfish remain, isn’t it a stroke of evolutionary luck that this animal possesses a bootstrap-pulling escape hatch in its DNA that allows it to create babies out of nothing more than necessity and dirty thoughts?

Well, yes. But also no. And kind of a hearty no, at that.

“What worries me is that maybe this is a sign that they’re on the way out,” says Andrew Fields, a Ph.D. student at Stony Brook University and lead author of the study, which was published in Current Biology last week.

Fields says he and his fellow researchers began their study hoping to investigate genetic diversity. Basically, they wanted to see how much inbreeding, if any, was taking place in the smalltooth sawfish population off the coast of southeastern Florida. What they found instead was that some of the animals sampled had been created without fertilization from a male. The sawfish weren’t inbred—they were clones.

“Maybe this process happened before, probably rarely, but we’re only seeing it now because there are so few sawfish,” says Fields. In other words, it’s not like female sawfish screw themselves for fun. Sexual reproduction and the genetic diversity that comes with it is a boon for species, aiding them in the ongoing fights against diseases, parasites, and environmental disruption. If there were males around, the females would gain more by mating with them than by going it alone. So even though it’s pretty cool that sawfish can reproduce by virgin birth, doing so is something of a Hail Mary

Photo: Florida Fish and Wildlife Conservation CommissionJuvenile smalltooth sawfish in the Charlotte Harbor estuarine system, Florida

“There is just no way on the face of the earth that this is some mechanism by which sawfish can save themselves from their plight,” says Nick Dulvy, a professor at Simon Fraser University and cochair for the IUCN Shark Specialists Group.

Among the four other species of sawfish, all are either endangered or critically endangered. Twenty countries where sawfish once flourished now have none. Another 43 nations have lost at least one sawfish species.

“What will save them is conservation,” says Dulvy.

Fins and oil from the animals fetch a pretty penny, as do the rostra, or saws, which go for several thousand dollars each. Dulvy says they find rostra for sale on eBay all the time. “Sawfish are so valuable at the first point of sale that fishermen in the developing world can pretty much retire when they catch one,” he says.

Globally, all sawfish species are protected by the Convention on the Conservation of Migratory Species of Wild Animals, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora bans any trade of sawfish parts. But in many countries, Dulvy says, these laws have far fewer teeth than the sawfish.

The good news is that the United States is doing better than most when it comes to sawfish conservation. The smalltooth sawfish has been on the Endangered Species List since 2003. In 2009, the National Oceanic and Atmospheric Administration designated critical habitat for them in the Fort Myers area of Florida’s Gulf Coast, as well as around the state’s southern tip.

Yet even in the States, where protections are enforced, the animals frequently get snagged on fishermen’s hooks and nets. Sawfish are less well-known than manatees or sea turtles, so lethal incidents sometimes occur out of ignorance, or as you see below, dumbassery.

“We are seeing a troubling number of incidents of mishandling by anglers, most of them coming through social media,” says Sonja Fordham, president of Shark Advocates International. She wonders whether it’s a result of too little money for public outreach or education, but either way, it has to stop.

Sawfish should never be taken out of the water, says Fordham, let alone dragged onto shore by their spiracles or nostrils. In fact, she says, everyone who catches one should release it as quickly and gently as possible, then alert the Fish and Wildlife Commission. When population numbers get as low as this fish’s, every data point matters.

But the best thing you can do for sawfish, experts told me, is to light a fire under your senator’s ass. “When you compare them to some other [listed] species, sawfish really aren’t getting their fair share,” says Fordham. “Look at Pacific salmon, marine mammals, and turtles, and you’ll see that sawfish don’t come close in terms of funding. Sawfish really need some champions in Congress.”

The smalltooth sawfish has forgone sex in a last-ditch effort for survival. The least we can do, the experts trying to save them say, is look up our representatives and shoot them an e-mail, because when it comes to fighting extinction, abstinence is definitely not the best policy.  


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