The remarkably clever dolphin has amused us with its tricks and intrigued us with its intelligence, and now it turns out that it routinely defies death. It can ignore a wound that would kill a human within hours. Dolphins, according to a new study, are frequently attacked by sharks that leave gaping holes bigger than a basketball.
"Why don't they bleed to death?" asks Michael Zasloff, professor of surgery and immunology at Georgetown University Medical Center. "Why don't they get infections? Why aren't they eaten after the injury? Why doesn't the shark finish the job?"
Zasloff thinks he may have at least partial answers to those questions, although much more research needs to be done.
"I have concluded that what we see when we look at the dolphin is a medical miracle," he said in a telephone interview. And if scientists can figure out exactly how the dolphin cheats death, maybe humans can eventually learn how to do it too, through better treatment of all sorts of injuries, not just shark bites.
Zasloff is a surgeon, not a dolphin expert, but his interest in this sea-going mammal began nine years ago when he was visiting a marine lab in Scotland. He was told that 70 to 80 percent of the dolphins that swim in the waters near Australia have shark bites.
"When I heard that I was taken aback," he said. "How in the heck does a mammal, like you and me, survive a shark bite in the ocean, unattended, with no antibiotics?"
A shark bite involves more than just ripping out a large chunk of flesh. The shark leaves "the worst collection of toxic organisms" in the wound, so infection should follow. A human being would die of infection and shock within two or three days if not hospitalized. So how does a dolphin heal itself without medical treatment?
That question haunted Zasloff for nine years, but a few months ago, he began working with Australians who are in constant contact with bottlenose dolphins, including Trevor Hassard, director of the Tangalooma Wild Dolphin Resort on Moreton Island. The resort is different from most aquatic parks in that the dolphins are free to visit, where they get an easy meal, or leave and return to the wild whenever they so desire.
No Obvious Pain, and No Scars
Over the years Hassard and others who care for wild dolphins have seen hundreds of dolphins that have been attacked by sharks. If the attack was recent, an open wound, usually on the backside of the dolphin, seemed to have little effect on the animal. It swam normally, did not show any sign of pain -- though dolphins clearly can experience pain -- and acted as though nothing was wrong. And within about 30 days the wound was gone. There were no scars. No signs of the injury. Even the natural contour of the body was back to its normal shape.
So the dolphin doesn't just recover from the attack. It regenerates the blubber and refills the hole.
"That's impossible," Zasloff said. "It's truly impossible."
How could it regenerate the blubber - which is actually a complex matrix of fibers, not just fat -- to heal itself?
Zasloff theorizes -- and this is just theory at this point -- that the injured dolphin can produce stem cells that can morph into whatever is needed to fill in the wound. Perhaps, he speculated, it has some sort of a growth hormone that stimulates the production of stem cells, and maybe that same hormone would work for other mammals, including humans. A lab with access to injured dolphins should be able to isolate the hormone, if it's there, he said.