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Discovery sheds light on jellyfish's limb-growing superpower

The ability for a jellyfish to regenerate body parts is often considered its 'superpower', but now researchers have found what is behind it.

Much mystery surrounds marine creatures in general, but jellyfish are among the most difficult to research. While a lot has been learned about these creatures in recent years, little is known about how they possess the unique ability to regrow dismembered body parts.

However, a team of Japanese scientists from Tohoku University has written in PeerJ to report that cellular mechanisms are behind this natural 'superpower'.

"Currently our knowledge of biology is quite limited because most studies have been performed using so-called model animals such as mice, flies, worms and fish etc," said Yuichiro Nakajima, corresponding author of the study. "Given that millions of species exist on earth, it is important to study various animals and broaden our knowledge."

For her study, the team looked at Cnidarian jellyfish that have been around for approximately 500m years and are known for their stinging cells. They form part of a unique group of animals that are not mutually symmetrical and also possess the capacity to regenerate body parts, something that humans have lost over time.

A jellyfish polyp against a black background.

A Cladonema polyp prior to becoming a jellyfish. Image: Sosuke Fujita, Tohoku University

The results

The team used Cladonema pacificum – a jellyfish species from Cnidaria phylum that has branching tentacles – to investigate the spatial pattern of cell proliferation and their roles during jellyfish development and regeneration.

The distribution of cells play a key role in DNA replication through cell division resulting in new 'daughter' cells identical to the 'parent' cell. This revealed distinct groups of proliferating cells in the sexual life-stage, appearing uniformly in the umbrella-shaped part of their body while clustered in the tentacles.

When food was withheld or cell proliferation was blocked, the team saw growth of the jellyfish stop and defects in the tentacle branching. This suggests that free-swimming adult jellyfish in the sexual stage have proliferating cells that play a key role in their body size, tentacle shape and regeneration.

Additionally, when food is available, the jellyfish gradually decrease in body size over 24 hours, showing them to adapt to their environments quite quickly.

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