‘Immortal’ jellyfish ages backwards and solely grows butthole when it wants one

New research has highlighted the versatility of a jellyfish, which grows a butthole only when it needs to.

A bizarre marine creature, named the Immortal Jellyfish – scientifically known as Turritopsis dohrnil – ages in reverse. When faced with stressful times, such as injuries of starvation, the fish can regress to a juvenile stage. Not only this, boffins have found another creature which can do the same, named the sea walnut or the warty comb jelly. Their regression is just the tip of the iceberg for these incredible animals.

They’re said to be able to fuse together with another jelly to survive severe injuries. Perhaps most surprisingly, they can grow and get rid of their own butthole when they need to.

Adding to this, they can also reproduce in their larval stage, which occurs before they mature into their recognisable jellyfish form. Previously, scientists also noticed they could get smaller in times of hunger, and grow when food is in abundance. Although there are suggestions this is not down to de-aging.

Marine biologist Joan Soto-Angel, from the University of Bergen in Norway, noticed the sea walnut’s form changing and decided to look into it. He paired up with Michael Sars Center colleague, Pawel Burkhardt, to investigate.

They put 65 of the creatures in separate tanks and starved them for 15 days. They were given small organisms to feed on once a week.

All of the sea walnuts got smaller, and they started regressing into their juvenile state.

15 of the jellies had lobes removed from their brains in surgery before the experiment to see if it made a difference – and it did. All of the creatures went back to a youthful form, and it was less common in the jellies who had surgery.

“The fact that we have found a new species that uses this peculiar ‘time-travel machine’ raises fascinating questions about how spread this capacity is across the animal tree of life,” Soto-Angel told the Proceedings of the National Academy of Sciences.

For the latest breaking news and stories from across the globe from the Daily Star, sign up for our newsletters.