In the open sea, a row of dolphins rubs against coral one after the other: At first glance, this seems bizarre, but has an important function for the clever sea creatures, as a research team discovers. They treat complaints and even take preventive measures.
Certain dolphins use corals and sponges to treat skin problems themselves. This is indicated by the study 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 targeted marine organisms and found 17 substances with antimicrobial properties, among other things.
“The result surprised us and we ventured the hypothesis that the dolphins use the corals and sponges to supply the skin with the beneficial substances contained therein prophylactically or in the event of existing irritations,” explains 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 in bottlenose dolphins in the northern Red Sea. The wildlife biologist was able to observe them up close on dives. “It took time to dive with the dolphins in a way that allowed for several exciting observations,” she says. Eventually, those corals and sponges could be identified that the marine mammals kept heading for.
The team found that the repeated rubbing caused tiny polyps that make up the coral community to shed mucus. To understand its properties, the researchers took samples. Analytical chemist and food scientist Morlock and her team examined these samples of gorgonian coral (Rumphella aggregata), leather coral (Sarcophyton sp.) and a sponge (Ircinia sp.). They came across the 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 skin microbiome and treat or prevent infection. One cannot prove a cure, says Morlock. But the conclusion is obvious “that rubbing on the marine organisms, which are rich in active ingredients and were specially selected by the dolphins, can make a difference because they have direct contact with the dolphin skin”.
Protecting marine mammals and their environment is very important to her, emphasizes wildlife biologist Ziltener. Many connections are not yet known. It is therefore necessary to do more studies “to show and understand the interaction of different species”.
6
