The top five saltiest, sexiest science discoveries in the sea from 2018.
*Blog co-authored by Marah J Hardt and Danielle Baldwin
Some people like it rough – whips and chains, but what about…chainsaws? For the endangered smalltooth sawfish, sex may not be that S & M, but having a three-foot long snout studded with teeth attached to their face does means "business time" can get a bit messy. And one can only wonder about reproduction itself—just imagine giving birth to a young with a serrated knife attached to its head—Happy Mother’s Day, indeed.
So how do they do it? We had few clues—until now. Despite their enormous size and shallow, nearshore habitat, sawfish, like so many other sharks and rays, have historically kept both their mating and birthing rituals hidden from scientists. But over the last six months, an explosion of scientific research on sawfish sex has advanced our knowledge of the species and contributed critical information to support their recovery.
The most recent findings build off work from about two years ago which first lifted the veil on sawfish reproduction. That’s when a team of researchers used DNA to prove female sawfish are capable of virgin birth—the first case of such parthenogenesis of any shark or ray in the wild. As discussed in Chapter 5: Inner Chambers in SEX IN THE SEA, the discovery hinted that when mates were hard to find—perhaps due to their low numbers because of overfishing—the females could continue to reproduce on their own. Parthenogenesis is a survival technique that could help with short-term recovery but, because of reduced genetic diversity, it’s not great for long-term success of the population.
This study gave us a peak behind the curtain of sawfish sex. For seventeen years, scientists had used surveys, satellite tracking, and tagging to identify pupping and nursery grounds, but we had still never witnessed live birth or confirmed where sawfish mated (even though females can reproduce sans males, they also do have sex).
That all changed in December of 2016, when Dr. Dean Grubbs, Associate Director of the Florida State University Coastal and Marine Laboratory, and his team witnessed a female giving live birth to several pups.
This rare encounter revealed just how these badass mamas endure the process: a thick sheath of tissue wrapped around the pup’s razor sharp rostrum when it is born protects the mother.
The unique biology of the birthing process wasn’t the only exciting find— the event also confirmed that sawfish give birth in the Bahamas. Before this, Florida was the only known pupping ground. Further research will help determine if the populations in Florida and the Bahamas intermix, which would be a good thing for boosting genetic diversity of the remaining populations.
Check out a video of the pregnant female and her pups by the Field School, here:
Then, in April of this year, Dr. Grubbs was able to confirm that male and female sawfish used the Everglades National Park as a lovers’ lane. "We’ve long assumed sawfish mating was a rough and tumble business, but we had never before seen fresh injuries consistent with recent mating, or any evidence that it was happening in areas we’ve been studying primarily as sawfish pupping grounds," said Dr. Dean Grubbs. "Figuring out where and when sawfish mate, and whether they do so in pairs or aggregations, is central to understanding their life history and ecology."
Bite marks and other scars are typical signs of the rough sex common in sharks and rays. By discovering fresh wounds on adult sawfish, the research team now suspects that the Everglades are not only where mama sawfish give birth, but also where the next generation is conceived.
This new information is vital for effective management of sawfish. In 2003, the smalltooth sawfish became the first native marine fish species listed as Endangered under the U.S. Endangered Species Act. Since that time, the additional four species of sawfish have all been added to either the Endangered or Critically Endangered lists as their natural populations dipped to less than 10% of their historic levels due to loss of natural habitat or overfishing. Sawfish are prized by some cultures not only for the uniqueness of their rostra, but for their fins and liver oil.
As of 2007, the import for sale of any sawfish species became illegal in the U.S. So while legislation is helping to save this species, understanding more about their mating habits is necessary to ensure effective conservation efforts. Now that the Everglades have been identified as both a pupping and mating ground of these endangered species, the continued protection of this critical habitat is even more important than ever.
These recent discoveries demonstrate that the science of sex in the sea continues to unfold at a rapid pace—and continued support of this basic research is paramount to effective management. This work also points to the importance of funding—not just for continued research, but also for continued protection and maintenance of the national parks that protect these animals. Protections that are currently under threat.
"Florida’s sawfish have a long road to recovery, but exciting breakthroughs so far provide lessons and hope for other endangered populations around the world," said Sonja Fordham, President of Shark Advocates International, a project of The Ocean Foundation. "The new findings can help efforts to protect sawfish at critical times, but also highlight the need to protect the park system that ensures suitable habitat, the funding for research, and the overarching law that has made success to date possible."
This link provides ideas for how to support national parks-- financially and beyond, including calling your representatives in the House and Senate and letting them know these special places matter to you (and while you are on the line, let them know you also support science-based decision making!). And if you are a scientist, consider adding your name to this recent letter, requesting continued support for our national marine protected areas.