larva

While studying comb jellies in a different tank, University of Bergen natural historian Joto J. Soto-Angel noticed that an adult ctenophore, also the species M. leidyi, had vanished from his tank and seemingly replaced by a larva.

"Witnessing how they slowly transition to a typical cydippid larva as if they were going back in time, was simply fascinating," Soto-Angel said in a statement.

"Over several weeks, they not only reshaped their morphological features, but also had a completely different feeding behavior, typical of a cydippid larva."

Dr Smith said this might have been caused by high concentrations of phosphorus in the ocean where this larva briefly lived and died.

Researchers generated three-dimensional images of miniature brain regions, digestive glands, a primitive circulatory system and even traces of the nerves supplying the larva’s simple legs and eyes.