Disposable guts save sea creature from predators

Tel Aviv University researchers have discovered a sea creature that ejects its digestive system when danger threatens, and then regenerates it within two weeks.

By JUDY SIEGEL-ITZKOVICH
Eilat's Coral Beach Nature Reserve has stunning reefs and an abundance of marine and fish life. (photo credit: NATIONAL NATURE AND PARKS AUTHORITY)
Eilat's Coral Beach Nature Reserve has stunning reefs and an abundance of marine and fish life.
(photo credit: NATIONAL NATURE AND PARKS AUTHORITY)
Tel Aviv University researchers have discovered a sea creature that ejects its digestive system when danger threatens, and then regenerates it within two weeks. They even wonder whether some day humans could use the same technique to renew vital organs. The research by Dr. Noa Shenkar and her student Tal Gordon, titled “Gut-spilling in chordates: Evisceration in the tropical ascidian Polycarpa mytiligera,” was published recently in Nature: Scientific Reports.
Shenkar and her team are surveying certain invertebrates living among the corals off the coast of Eilat. It was there that they discovered the talented member of the ascidian family, and they took several to their lab. What they saw was “like science fiction.” When even a small amount of mechanical pressure is applied to it by a predator, the creature expels its unpalatable digestive organs. The mechanism makes the creature very successful; this species is the most common type in the Eilat coral reefs, and among the most common in reefs around the world.
The ejection of internal organs is a well-known phenomenon in sea-cucumbers.
But it was not known in other creatures such as Polycarpa mytiligera, which is small and simple looking. Shenkar, a marine biologist, noted that many living things can regenerate missing parts – for example lizards regrow their tails, starfish regrow their arms and flatworms can restore whole sections of their bodies. However, these body parts are not essential to their survival. The Polycarpa mytiligera can not only eject and regrow vital organs, but can manage without them for a limited time.
“It seems that mankind has a lot to learn from this creature,” said Shenkar.
As it is brown and usually covered with all kinds of other creatures, it is well camouflaged.
Fish usually don’t feed on it, as it is not tasty to them, said Shenkar. If a fish bites into one, it spits it out immediately.
“We still don’t know the compound that gives it a bad taste. The ejection of its organs is a way of telling potential predators: ‘Don’t touch me or eat me. I am not tasty,’” the TAU biologist suggested.
Regarding the possibility of implications for human health, she said that the ascidian, which is commonly found, could serve as an excellent model for future medical research on renewing soft tissue.
“We believe that these planned studies can advance understanding toward future developments in regenerating human tissue,” concluded Shenkar.
ANIMAL SPECIES PRODUCE OWN SUNSCREEN
Researchers have discovered why many animal species can spend their whole lives outdoors with no apparent concern about high levels of solar exposure – they make their own sunscreen.
The findings, published recently in the journal eLife by scientists from Oregon State University, found that many fish, amphibians, reptiles and birds can naturally produce a compound called gadusol, which among other biologic activities provides protection from the ultraviolet, or sun-burning component of sunlight.
The researchers also believe that this ability may have been obtained through some prehistoric, natural genetic engineering.
According to the study, the gene that provides the capability to produce gadusol is remarkably similar to one found in algae, which may have transferred it to vertebrate animals and because it’s so valuable, it has been retained and passed along for hundreds of millions of years of animal evolution.
“Humans and mammals don’t have the ability to make this compound, but we’ve found that many other animal species do,” said pharmacy professor Taifo Mahmud who was lead author of the research.
The genetic pathway that allows gadusol production is found in animals ranging from rainbow trout to the American alligator, green sea turtle and farmyard chicken.
“The ability to make gadusol, which was first discovered in fish eggs, clearly has some evolutionary value to be found in so many species,” Mahmud said. “We know it provides UV-B protection, it makes a pretty good sunscreen. But there may also be roles it plays as an antioxidant, in stress response, embryonic development and other functions.”
The researchers also found a way to naturally produce gadusol in large amounts using yeast. With continued research, it may be possible to develop gadusol as an ingredient for different types of sunscreen products, cosmetics or pharmaceutical products for humans. Instead of rubbing the sunscreen on, it could be a systemic one in humans that they could swallow, he suggested.