A fascinating discovery has emerged from the depths of the ocean: the Atlantic comb jelly, affectionately nicknamed the “sea walnut,” possesses the extraordinary ability to reverse its aging process. This remarkable finding, published in the preprint database BioRxiv, highlights the sea walnut’s (Mnemiopsis leidyi) resilience in the face of adversity.
When confronted with limited food resources or physical injury, this gelatinous invertebrate undergoes a remarkable transformation, regressing back to its larval form. This larval stage, equipped with two tentacles, allows the sea walnut to efficiently catch food. In contrast, the adult form, resembling a pair of translucent lungs, lacks these crucial tentacles.
The sea walnut now joins a select group of only two other known species capable of reversing their development as adults: the immortal jellyfish (Turritopsis dohrnii) and the dog tapeworm (Echinococcus granulosus). This discovery suggests that age reversal might be a more widespread phenomenon than previously thought.
The sea walnut, native to the western Atlantic Ocean, has become an invasive species in Europe and Asia. Its ability to survive for weeks in the ballast water of ships, even without food, explains its successful transatlantic journey. The sea walnut’s presence in the Black and Caspian seas has significantly impacted local fisheries by outcompeting native creatures for food resources.
To understand the sea walnut’s survival strategies, researchers conducted experiments where one group was starved and another group experienced tissue removal. Remarkably, these comb jellies, known for their regenerative abilities, shrunk into tiny blobs but did not perish. Upon reintroduction of food, an astounding 13 out of 65 sea walnuts exhibited the growth of tentacles, indicating their regression to the larval stage.
According to Joan J. Soto-Angel, a marine biologist at the University of Bergen, Norway, this larval stage allows the sea walnuts to access a new ecological niche by using their tentacles to capture food sources unavailable to their adult form. With ample food, the sea walnuts eventually regain their original size, regenerate their lobes, and even recover their reproductive capabilities.
The discovery of this third animal capable of aging in reverse has surprised scientists. While the sea walnut’s regression process differs from the immortal jellyfish, both species offer valuable insights into the intricacies of aging. Comb jellies, being one of the oldest existing animal lineages, hold significant potential for studying evolution.
However, some scientists remain cautious about definitively concluding that the sea walnut truly reverses its age. Yoshinori Hasegawa, a zoologist at the Kazusa DNA Research Institute in Japan, suggests that the observed changes might be more akin to a shrinking process rather than a complete reversal of aging. The sea walnut’s remarkable ability to revert to a younger state, regardless of its exact nature, underscores the fascinating diversity and resilience of life on Earth.