Sea Walnut’s can age in reverse: A breakthrough discovery in comb jellies | – Times of India

For most animals, ageing is a one-way process. However, the sea walnut, a comb jelly native to the eastern Atlantic Ocean, defies this norm. When faced with harsh conditions, this transparent invertebrate can revert to a tentacled larval stage. Once conditions improve, it matures back into an adult. This fascinating ability of Mnemiopsis leidyi was detailed in a recent preprint on bioRxiv.The jellyfish’s ability to reverse age may explain its success as an invasive species, first in the Black Sea and now across parts of Europe and Asia. This discovery might also offer new insights into the process of aging.This species was the first known to exhibit reverse ageing.

Jellyfish regeneration: Breakthrough discoveries

The team eventually optimised conditions for the animals, allowing them to complete initial studies on the species’ nervous system. They then pushed the creatures to their limits by depriving them of food or amputating parts of their gelatinous bodies. Despite their severe condition, the animals did not die. Upon refeeding, some jellies revived, with 13 out of 65 regrowing two tentacles typical of their larval stage. These tentacles helped the revived jellies hunt plankton. This potential advantage in capturing food might contribute to their invasive success, though this hypothesis needs further investigation. With adequate nourishment, the jellies eventually regenerated their lobes and resumed reproduction.

Unexpected findings in comb jellies

Previously, biologists had only observed the ability to revert to an earlier life stage in the immortal jellyfish and a tapeworm species, Echinococcus granulosus. Finding this capability in the comb jelly—a member of the Ctenophores phylum, distinct from jellyfish—was unexpected, according to Soto-Angel.
While both the immortal jellyfish and comb jellies can revert to a younger stage, they do so differently. Jellyfish undergo a cellular transformation, losing their cellular identities and merging into a “cyst” that then differentiates into a polyp.

Comb jellies: Future implications

In contrast, comb jellies appear to rejuvenate as the exact same individual. Yoshinori Hasegawa, a zoologist at the Kazusa DNA Research Institute, who was not involved in the study, considers this finding significant but questions if the comb jellies are genuinely reversing their biological clocks or merely shrinking. Despite this, the discovery suggests that other species may also possess rejuvenation capabilities.