Imma Perfetto
Cosmos science journalist
Timelapse showing reverse development in a lobectomized individual of M. leidyi. Credit: Soto-Angel and Burkhardt (2024), PNAS, “Reverse development in the ctenophore Mnemiopsis leidyi“. https://doi.org/10.1073/pnas.2411499121
Who knew you could be jealous of a comb jelly? Thats right, scientists have discovered that a ctenophore, also known as a comb jelly, can age in reverse.
This alternate development, say the researchers, ultimately allows M. leidyi to escape “the normal ontogenetic fate (i.e., senescence)” otherwise known as biological ageing.
The ctenophore (pro: teena-four) species, Mnemiopsis leidyi, can reverse its development from an adult back to a larva.
The miraculous finding is published in the journal Proceedings of the National Academy of Sciences (PNAS).
“The work challenges our understanding of early animal development and body plans, opening new avenues for the study of life cycle plasticity and rejuvenation,” says Joan J. Soto-Angel, a postdoctoral fellow in the Department of Natural History at the University of Bergen in Norway, and co-author of the study.
“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.”
The ability of an organism to reverse its development back to a preceding life cycle is incredibly rare. Before now, it was thought to occur only in a few species of cnidarians – (pro: need-arians) the phylum which includes aquatic animals like jellyfish, sea anemones, and corals.
Only a single species, the “immortal jellyfish” Turritopsis dohrnii, was known to have the ability to revert to a polyp after becoming fully grown and sexually mature adult.
M. leidyi is from a different phylum of marine invertebrates (animals without a spine) the ctenophores, which is among the earliest animal lineages to have diverged.
Soto Angel made the remarkable discovery by chance when he noticed an adult M. leidyi had vanished from a tank in the laboratory and been replaced by a larva.
To find out if these were the same individual, Soto Angel and co-author Pawel Burkhardt, group leader at the Michael Sars Centre at the University of Bergen, designed experiments to try and reproduce this phenomenon under controlled conditions.
They found that when M. leidyi was exposed to the stress of starvation and physical injury, it was able to shift from its fully formed lobate stage back to its larval stage.
“Witnessing how they slowly transition to a typical cydippid larva as if they were going back in time, was simply fascinating,” says Soto Angel.
“Over several weeks, they not only reshaped their morphological [physical] features, but also had a completely different feeding behaviour, typical of a cydippid larva.”
This alternate development pathway ultimately allows M. leidyi to escape the fate of ageing.
“This is a very exciting time for us,” says Burkhardt.
“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.”
The Ultramarine project – focussing on research and innovation in our marine environments – is supported by Minderoo Foundation.