Dolphins heal remarkably well after massive shark bites, and scientists want to know how they do it.
Diving into dolphin healing. I’m Bob Hirshon and this is Science Update.
Dolphins are known for their keen intelligence. But Georgetown University medical scientist Michael Zasloff has focused on their amazing healing abilities. He and Australian conservationist Trevor Hassard have been documenting how dolphins routinely recover from huge shark bites within a month.
And in this month, that deficit is filled, and you don’t see scars. There is no evidence of infection – there’s no swelling, without any antibiotics – and what’s equally remarkable is they definitely show no pain.
How they do it remains to be seen, but Zasloff suspects that two key factors are antibiotic compounds in dolphin blubber, and the dolphins’ ability to minimize blood flow to the surface of their bodies. Zasloff has also studied healing properties in frog and shark skin, but he’s excited about dolphins because they’re mammals, and therefore more relevant to human medicine. I’m Bob Hirshon for AAAS, the Science Society.
Making Sense of the Research
If a shark bit off a football-sized chunk of your back, chances are you'd bleed to death. Even if you were lucky enough to get immediate medical attention, you'd certainly never be the same. But it turns out that this sort of thing happens to dolphins all the time. And the dolphins usually recover so well that within a month, you wouldn't even know it happened.
Zasloff became interested in this subject about ten years ago, and he says that although dolphins' healing abilities are widely known among dolphin handlers and marine biologist, very little research has been done on how it works. There are some experimental challenges: for instance, it wouldn't be ethical to intentionally injure dolphins to study their healing, or to put them in a tank full of sharks. And capturing wild dolphins that just happened to have sustained a recent shark bite is hardly easy.
However, Zasloff believes that figuring out a way to study dolphin healing would be worthwhile. His guesses about how it works are based on what we do know about dolphin tissue. Firstly, we know from studying dolphin blubber that it contains antimicrobial chemicals. "It's most likely that the dolphin stores its own antimicrobial compound and releases it when an injury occurs," Zasloff predicts. In other words, it has a built-in antiseptic to keep wounds clean.
It's also known that when dolphins dive deep to look for prey, the blood vessels near the surface of their skin constrict. That helps conserve oxygen, by directing most of the blood supply to essential organs like the heart and brain. It's part of the “diving reflex” that happens in all mammals, including humans. But since dolphins dive much deeper and longer than humans can, their diving reflex is especially strong. Zasloff suspects that they can also take advantage of this reflex to restrict blood flow after an injury, which prevents the dolphin from bleeding to death.
Finally, because the dolphins heal with little visible scarring, and fill in the missing tissue, Zasloff believes that the healing process must be a form of regeneration. When tissue regenerates, it replaces the missing cells with identical tissue, rather than just covering the wound with a scar. In adult humans, the only organ that truly can regenerate is the liver; however, fetuses can regenerate other kinds of tissue while still in the womb. So it's possible that dolphins have retained the ability to revert their cells to a fetal state, while humans and land mammals, for some reason, lose that ability after birth. It's believed that turning off this regenerative ability helps protect against cancer, but why that would be more of a concern to land mammals than marine mammals remains unclear. It's hoped that understanding and imitating dolphin healing will lead to new therapies for human injuries.
Now try and answer these questions:
- What's unusual about dolphin healing?
- How does a dolphin heal a major wound differently from a human?
- What are some known characteristics of dolphins that may contribute to their healing abilities?
- What kinds of specific questions might future experiments ask?
You may want to check out the August 5, 2011, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: Dolphins that heal themselves, and dolphins that use electroreception in addition to echolocation. Also, How vampire bats find their prey, and how a Cuban plant takes advantage of a bat’s ability to echolocate.
Dolphin Brains is a Science Update about the keen intelligence of dolphins.
Dolphin Brains is a Science Update lesson about the keen intelligence of dolphins.