There are very few species in nature that are capable of “reversing the timeline.” According to a study funded by the Michael Sars Center at the University of Bergen, Norway and the European Research Council grant, sea walnut (Mnemiopsis leidyi) is one of them.
The finding published in the magazine scientific Pnas, illuminates central aspects of the development, ecology and evolution of the ctenorophs phylum, and shows the high potential of M. leidyi as a unique system to study reverse development and rejuvenation.
Sea nut and jellyfish
Many ctenophores, also called “comb jellies”, are part of the oldest extant lineages; They belong to the phylum of animals characterized by the presence of coloblasts, cells that produce a sticky substance used to capture prey. Recent studies supporting their phylogenetic position place them as a vital model for studying evolutionary innovations potentially rooted in the deepest branches of the animal tree of life. Its life cycle and plasticity have not yet been exploited enough to draw conclusions at the phylum level, but it is recognized that its biological cycle includes the planktonic, bitentaculate cydipid stage; also present in species such as Platyctenida, which lives on rocks, algae, soft coral or on the body surface of other invertebrates.
Although ctenophores are also called “jellyfish” they are from a different phylum, and are only similar because of their gelatinous and semi-transparent body. The sea nut is part of the species Ctenophora, while conventional jellyfish belong to the phylum Cnidaria; The latter includes species that we recognize for their ability to rejuvenate, the best known being Turritopsis dohrnii or the “immortal jellyfish.” The researchers report that from now on the sea nut joins the list: “We have shown that the mature lobate stages of M. leidyi are capable of returning to their larval state after a period of stress,” theorizes Joan Soto-Angel, lead author of the study and marine biologist at the University of Bergen. He adds that the fact of having found a new species that uses this “machine of “Time Travel” raises fascinating questions about how widespread the capacity for life is in the animal kingdom.
A team of researchers inserted old oocytes into the ovaries of young mice to create rejuvenated reproductive cells.
What does the study refer to?
Previous research had concluded that the transition from the larval to the adult state was irreversible in this species. Soto-Angel proposed the idea to his team after an adult specimen of the sea nut “disappeared” from his tank; in reality, it had become a larva, that is, it had rejuvenated.
At that time, he and Pawel Pawel Burkhardt, second author of the study, attempted to systematically reproduce the conditions that cause rejuvenation in M. leidyi. To do this, they kept a total of 65 adult sea nut specimens in isolated tanks: they were fasted for fifteen days, and then they were fed once a week with a smaller amount of food than normal. In addition, 15 of the 65 had one of the gelatinous lobes that make up their body surgically removed.
Fasting triggered the rejuvenation process, and with the removal of one of the lobes it was even more effective. According to their conclusions, 40% of the animals subjected to the double treatment completely regressed to the larval phase, while only 14% of those subjected to prolonged fasting completely rejuvenated. “This fascinating result will open the doors to many important discoveries. It will be interesting to unravel the molecular mechanism that drives reverse development and what happens to the animal’s nervous network during this process,” concludes Burkhardt.
Article originally published in WIRED Italy. Adapted by Alondra Flores.
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