Reverse development, the rejuvenation process by reverting to an earlier life stage is believed to be limited to a few species within the phylum Cnidaria. *Turritopsis dohrnii* is the only known species capable of this process after it reaches sexual maturity.
In a new study, researchers led by Joan J. Soto-Angel, a Michael Sars Centre alumnus and current postdoctoral fellow at the Department of Natural History and University Museum of Bergen, report that the comb jelly Mnemiopsis leidyi is capable of reversing from mature lobate to early cydippid.
Soto-Angel explained, “We showed that mature lobate stages of M. leidyi can reverse to a cydippid larval stage after a period of stress. 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.”
Ctenophores, or comb jellies, are known for their regenerative abilities and unique reproductive traits of sexually reproducing at the larval stage, complicating the distinction between adulthood and immaturity. While earlier studies suggested that the transition from larva to adult was irreversible, Soto-Angel noticed an adult ctenophore seemingly disappear from a tank, replaced by a larva.
This observation sparked his curiosity, leading him, along with Pawel Burkhardt from the Michael Sars Centre, to design experiments to test whether such a reversion could occur under controlled conditions.
When exposed to stressors like starvation and physical injury, *Mnemiopsis leidyi* exhibited an extraordinary ability to revert from its adult lobate form to a cydippid larval stage. Over several weeks, the adult ctenophores reshaped their morphology and adopted feeding behaviors typical of cydippid larvae.
This observation expands our understanding of developmental flexibility in ctenophores, positioning *Mnemiopsis leidyi* as a valuable model for research in developmental biology and aging. Given that comb jellies are among the earliest animal lineages, these findings suggest that reverse development may be an ancient trait in the animal kingdom.
Burkhardt said, “This is a very exciting time for us. This fascinating finding will open the door for many important discoveries. It will be interesting to reveal the molecular mechanism driving reverse development and what happens to the animal’s nerve net during this process.”
Journal Reference:
- Joan J. Soto-Angel, Pawel Burkhardt. Reverse development in the ctenophore Mnemiopsis leidyi. PNAS. DOI: 10.1073/pnas.2411499121