If a human being develops a rash, he can go to the doctor for an ointment. Dolphins also suffer from skin conditions and, in the absence of doctors, self-medicate. In fact, queue up to rub against corals and sponges, but only against those that have medicinal properties; that is, select certain marine invertebrates to cure their epidermal diseases.
The surprising discovery has just been published in the prestigious journal ‘Science’ by a team of scientists from Germany, Switzerland and Egypt. It all started thirteen years ago, when study co-lead author Angela Ziltener, a wildlife biologist at the University of Zurich, Switzerland, first observed dolphins rubbing against coral in the Red Seaoff the coast of Egypt.
Ziltener and his team noticed that the dolphins selected the corals they rubbed against and set out to understand why. “I had not seen this previously described coral rubbing behavior, and it was clear that the dolphins knew exactly which coral they wanted to use”, recalls Ziltener, who thought there must be a reason and set himself the goal of discovering it.
The Swiss biologist decided to study the dolphins up close because she is a diver. It took her some time to gain the trust of a pod of Indo-Pacific dolphins (Tursiops aduncus), but finally succeeded. Once the group allowed him to visit regularly, Ziltener and his colleagues were able to identify and sample the corals the dolphins rubbed against.
The researchers, who conducted the study in Egypt’s Northern Red Sea, found that, taking turns repeatedly rubbing against the corals, the dolphins agitated the tiny polyps that make up the coral communitya, and these invertebrates released mucus. To understand what properties the mucus contained, the team collected samples from the coral.
When lead author Gertrud Morlock, an analytical chemist and food scientist at Justus Liebig University Giessen in Germany, and her team analyzed samples of the gorgonian coral Rumphella aggregata, coral leather Sarcophyton sp., and the sponge Ircinia sp.They found 17 active metabolites with antibacterial, antioxidant, hormonal and toxic properties.
The discovery of these bioactive compounds led the team to conclude that mucus from corals and sponges serves to regulate the dolphins’ skin microbiome and treat infections.
“Repeated rubbing allows the active metabolites to come into contact with the dolphins’ skin,” says Morlock. “These metabolites could help (dolphins) achieve skin homeostasis and be useful for prophylaxis or ancillary treatment against microbial infections”.
Scientists point out that the reefs where these corals are found are important places for local populations of dolphins. They use them to rest and have fun. For these intelligent animals they are both bedrooms and play areas.
“Between naps, dolphins often wake up to rub against coral. Is almost as if they were taking a shower, cleaning themselves before going to sleep or getting up to start the dayMorlock explains. The scientists also found how dolphin mothers teach their calves to rub against medicinal corals and sponges.
The danger of tourism
The concern, now, is double. On the one hand, climate change, which threatens to destroy coral reefs from all over the world, and on the other the growing tourism. Ziltener has noticed a disturbing trend since she began researching dolphins in Egypt in 2009.
“The tourism industry makes a lot of money off the dolphins. People dream of swimming with them, so they’re finding out what reefs they use and hassling them if they don’t follow the guidelines on how to approach them. responsibly,” warns Ziltener.
The biologist is so concerned that she has founded an organization called Dolphin Watch Alliancea conservation group that educates tour guides, tourists, and the general public on how to provide safe experiences for dolphins, and pushes for reefs to become protected areas.
Ziltener and his team they hope the reefs remain a safe place for dolphinsand thus be able to continue studying the behavior of these mammals, and identify which corals and selected sponges are used to heal specific parts of the body.
Reference study: https://www.cell.com/iscience/fulltext/S2589-0042(22)00541-7
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