Biology: Dolphins nourish their skin with coral

Certain dolphins use corals and sponges to self-treat skin problems. This is indicated by the research results of an international research team published in the journal “iScience”. Indo-Pacific bottlenose dolphins (Tursiops aduncus) have been observed in the Red Sea off the coast of Egypt rubbing and queuing against selected corals and sponges. The scientists examined the target marine organisms and found, among other things, 17 substances with antimicrobial properties.

“The result surprised us and we ventured into the hypothesis that dolphins use corals and sponges to supply the skin with useful substances found in them prophylactically or in case of existing irritations,” explains Professor Gertrud Morlock from the University of Giessen. She led the study together with Angela Ziltener from the University of Zurich.

Ziltener first saw the unusual behavior 13 years ago among bottlenose dolphins in the northern part of the Red Sea. A wildlife biologist was able to observe them up close during the dive. “It took time to dive with the dolphins in a way that allowed for some exciting observations,” she says.

Corals and sponges secrete substances

Eventually, those corals and sponges that the marine mammals moved on to could be identified. The team found that repeated rubbing caused mucus to be expelled from the tiny polyps that make up the coral community. To understand its properties, researchers took samples.

Analytical chemist and food scientist Morlock and her team examined these samples of gorgonian coral (Rumphella aggregata), leathery coral (Sarcophyton sp.) and sponge (Ircinia sp.). They found 17 biologically active substances with antimicrobial, antioxidant, hormonal and toxic properties.

Their discovery led the researchers to believe that the mucus serves to regulate the dolphin’s skin microbiome and treat or prevent infection. There is no proven cure, Morlock says. But the conclusion is obvious “that rubbing on marine organisms, which are rich in active ingredients and specifically chosen by the dolphins, can make a difference because they have direct contact with the dolphin’s skin”.

The protection of marine mammals and their environment is very important to her, emphasizes wildlife biologist Ziltener. Many connections are not yet known. Therefore, more studies need to be done “to show and understand the interaction of different species”.


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