(CN) — Indo-Pacific bottlenose dolphins repair skin and stay healthy by repeatedly rubbing up against corals that have natural medicinal properties, according to new research.
The study published Thursday in the journal iScience found dolphins along the coral reefs off the coast of Egypt in the Red Sea appear to be self-medicating their skin ailments.
When lead author Gertrud Morlock, an analytical chemist and food scientist at Justus Liebig University Giessen in Germany, and her team analyzed samples of coral from the waters where they had observed Indo-Pacific bottlenose dolphins repeatedly rubbing themselves from head to tail along the reefs, they found 17 active metabolites with antibacterial, antioxidative, hormonal and toxic activities.
Discovery of these bioactive compounds led the team to deduce that the mucus in the corals and sponges helps regulate dolphin skin and treat infections.
“Repeated rubbing allows the active metabolites to come into contact with the skin of the dolphins,” Morlock said in a statement. “These metabolites could help them achieve skin homeostasis and be useful for prophylaxis or auxiliary treatment against microbial infections.”
Co-lead author Angela Ziltener, a diver and wildlife biologist at the University of Zurich, has studied dolphins for over a decade in the Egyptian Red Sea up close while diving.
Dolphins are typically studied from the surface of the water, but Ziltener’s abilities as a diver allowed her to study the dolphins up close after she earned the pod’s trust, which she was able to do in part because the dolphins she was studying weren’t bothered by the large bubbles released by her diving tanks.
“Some dolphins, like spinner dolphins in the Southern Egyptian Red Sea, are shyer about bubbles,” Ziltener explained.
When Ziltener and her team first observed dolphins rubbing along the corals off the coast of Egypt in 2009, they also noticed that the dolphins appeared to be selective about which coral they rubbed against. The researchers wanted to understand why.
“I hadn’t seen this coral rubbing behavior described before, and it was clear that the dolphins knew exactly which coral they wanted to use,” Ziltener said in a statement. “I thought, ‘There must be a reason.’”
Once the pod was comfortable enough with Ziltener’s visits, the team was able to identify and sample the corals the dolphins were rubbing on.
They found that by repeatedly rubbing against the corals, Indo-Pacific bottlenose dolphins were agitating the little polyps that create the coral community and causing the invertebrates to secrete mucus. The team collected samples of the corals to turn over to Morlock for research.
What the scientists discovered amazed them: The coral and sponges contained properties that were healing and fortifying the dolphins’ skin.
The reefs where the corals are found are important places for local dolphin populations. Dolphins go there to rest and relax.
“Many people don’t realize that these coral reefs are bedrooms for the dolphins, and playgrounds as well,” Ziltener said.
The dolphins alternate between taking naps on the corals and waking to rub against them.
“It’s almost like they are showering, cleaning themselves before they go to sleep or get up for the day,” Ziltener said.
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