Why do dolphins rub against corals?

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When you have a rash, you go to the doctor or the pharmacy and you can come out with an ointment as a remedy. Indo-Pacific bottlenose dolphins also suffer from skin conditions, but get their medicine by lining up to rub against coral. A new study published in ‘Science’ shows that these marine invertebrates have medicinal properties, suggesting that dolphins use them to treat skin conditions such as fungal infections.

Thirteen years ago, Angela Ziltener, a wildlife biologist at the University of Zurich, Switzerland, first observed a pod of dolphins brushing against coral in the northern Red Sea off the coast of Egypt. She and her team noticed that the dolphins were picky about which corals they rubbed against and wanted to figure out why. “I had never seen this behavior before, and it was clear that the dolphins knew exactly which coral they wanted to use.”says the researcher. He thought there must be a reason.

Since Ziltener is a diver, she was able to study the dolphins up close. It took her a while to gain the trust of the group, but once the animals allowed her to visit them regularly, she and her colleagues were able to identify and sample the corals the dolphins rubbed against. Researchers have found that by repeatedly rubbing against corals, Indo-Pacific bottlenose dolphins wiggle the tiny polyps that make up the coral community, and these invertebrates release mucus. To understand the properties contained in the mucus, the team took samples of coral.

Dolphins favorite corals

Gertrud Morlock, an analytical chemist at Justus Liebig University in Giessen, Germany, and her team studied samples of dolphin-favorite corals and sponges (Rumphella aggregateata, Sarcophyton sp., Ircinia sp..), with high-resolution mass spectrometry and other techniques and found 17 active metabolites with antibacterial, antioxidant, hormonal and toxic activities.

This discovery of these bioactive compounds led the team to believe that mucus from corals and sponges serves to regulate the dolphins’ skin microbiome and treat infections. “Repeated rubbing allows active metabolites to come into contact with dolphin skin”explains Morlock. “These metabolites could help them reach skin homeostasis and be useful for prophylaxis or adjunctive treatment against microbial infections”he specifies.

clean up before sleep

The reefs where these corals are found are important places for local dolphin populations. They go there to rest and have fun. “Many people don’t realize that these coral reefs are sleeping quarters for dolphins and also play areas”said Ziltener. Between naps, dolphins often wake up to perform coral rubbing behavior. “It’s almost as if they take a shower, wash themselves before going to sleep or getting up”it is said.

Since he began researching dolphins in Egypt in 2009, Ziltener has noticed a disturbing trend. “The tourism industry now makes a lot of money swimming with dolphins. People dream of swimming with them, so they find out what reefs they use and disturb these mammals if they don’t follow guidelines on how to swim with them. approach responsibly.”, He says. For this reason he formed Dolphin Watching Alliancea conservation group that educates tour guides, tourists and the general public on how to provide tourists with safe experiences for these mammals, and has lobbied for the reefs to become protected areas.

The researchers hope that as long as the reefs remain a safe place, they can continue to study coral friction and identify which selected corals and sponges are used for specific body parts.

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Reference article: https://www.abc.es/ciencia/abci-delfines-hacen-cola-para-fritarse-contra-corales-202205192011_noticia.html

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