Jellyfish Can Regrow Their Tentacles, And We Finally Know How : ScienceAlert


Jellyfish don’t seem to have much of a problem. They are gelatinous blobs with no brain, heart, or blood, and are often at the mercy of ocean currents.

But that doesn’t mean it’s simple. Far from it. They are highly efficient and one of the most successful animal groups on Earth.

One of the keys to its success is the jellyfish’s tentacles. These are long tentacles that wrap around their prey and deliver a paralyzing toxin for the jellyfish to digest in peace. If something goes wrong with these tentacles, the jellyfish can easily regenerate them in a very short time.

Studying tiny jellyfish the size of a fingernail called jellyfish pacific cladonema, A research team led by biologist Sosuke Fujita from the University of Tokyo has finally revealed the cellular mechanism behind this amazing healing act.

From insects to vertebrates such as salamanders, the key to regeneration is a mass of cells called blastocytes. We now know that jellyfish partially grow their blastema cells from a tissue called repair-specific proliferating cells. Stem-like cells that are actively proliferating and dividing, but have not yet differentiated. These are very similar to stem cells in that they can become anything depending on the host’s needs.

A series of images showing the regeneration process of a tentacle up to 72 hours after amputation. (Sou Fujita, University of Tokyo)

“Importantly, these stem-like proliferating cells in the blastema are different from the resident stem cells localized in the tentacles,” says biologist Yuichiro Nakajima of the University of Tokyo. “Repair-specific proliferating cells primarily contribute to the newly formed tentacle epithelium (thin outer layer).”

To find out how jellyfish behave, researchers carefully removed the tentacles, waited for the regeneration process to begin, then euthanized the animals and applied different stains to label different cells. used for dissection.

In fact, jellyfish constantly have stem cells hanging in or near their tentacles. These are cells that have not yet been assigned a function and can develop into any type of cell that the body needs. These are used for ongoing maintenance and body repair throughout the jellyfish’s life.

However, repair-specific proliferating cells appear only when the jellyfish is injured and are specific for repairing and regenerating damaged body parts. This resembles the repair-specific cells found in salamanders and develops bilaterally symmetrically, in contrast to the bizarre radial development of the jelly.

Stem cells (green) and proliferating cells (red) resident in the tentacles of a regenerating jellyfish. (Sou Fujita, University of Tokyo)

“In this study, our aim was to use the tentacles of the cnidarian jellyfish to address the mechanisms of blastogenesis. cladonema “As a regeneration model for non-bilateral people,” Fujita explains.

“Given that repair-specific proliferating cells are similar to restricted stem cells in the limbs of bilateral salamanders, the formation of blastema by repair-specific proliferating cells has been linked to complex organs and appendages during animal evolution. We can infer that this is a common characteristic acquired independently for organ regeneration.”

Salamanders and jellyfish are very different from each other. The last common ancestor of jellyfish and bilateral animals lived hundreds of millions of years ago, and distinct evolutionary paths are evident. So it will be very interesting to find a repair mechanism that is common to both. That could suggest some kind of convergent evolution, where very different organisms develop similar traits independently.

What we currently do not have are tools to discover how repair-specific proliferating cells emerge in jellyfish. This is an important next step, the researchers say. Because it will help find ways to give humans the ability to regenerate body parts.

“Ultimately, understanding the mechanisms of blastogenesis in regenerating animals, including jellyfish, may help us identify cellular and molecular components that improve our own regenerative abilities.” Professor Nakajima says.

This study PLOS Biology.



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