Introduction:
The process of regeneration in jellyfish is quite similar to the regeneration process in amphibians and other animals. All animals capable of regeneration begin the repair process by forming a mass of proliferating cells known as the blastema. These cells, which resemble stem cells, can replenish body parts by dividing repeatedly. Although the cells remain undifferentiated at first, they eventually transform into specific cell types such as muscle and skin.
Blastema formation in jellyfish:
The process of blastema formation has been studied in some other animals, but how it is formed in jellyfish has remained a mystery until now. A research team led by researcher Susuki Fujita from the University of Tokyo and Tohoku University in Japan aimed to establish a basis for non-bilaterian regeneration by understanding how the blastema aids in regrowing tentacles in jellyfish. Would their process of blastema formation be different from that in bilaterians?
New discovery about the regeneration process in jellyfish:
The Japanese team finally uncovered a new insight into this process in the jellyfish Cladonema pacificum. They found that the proliferating cells forming the blastema appear only in the case of injury – they are not the same as the local stem cells present at the base of the tentacle. However, both types of cells work together to repair and regrow the severed tentacle.
Regeneration in jellyfish:
Jellyfish are animals belonging to the phylum Cnidaria, which are invertebrates with soft bodies. The jellyfish also include corals, hydra, and anemones, all of which have stinging tentacles. Unlike bilaterians such as amphibians (and humans), which have bilateral symmetry (meaning there are identical right and left sides), jellyfish have radial body symmetry, with body parts radiating from the center and being symmetrical in all directions. They do not have a right and left side or a front and back.
The process of tentacle regeneration in jellyfish:
Since jellyfish rely on their tentacles to capture and immobilize prey, they need to regrow a lost tentacle as quickly as possible. When a tentacle from Cladonema is severed while the base remains in place, the wound at the cut site heals completely within 24 hours. The blastema forms immediately after healing; then, the new tentacle begins to grow.
The cell proliferation process in jellyfish:
When the blastema is formed, most of the cell proliferation occurs towards the regenerating tip of the new tentacle. Three types of differentiated cells have been identified in the blastema. These epithelial cells form the inner layers of the tentacle; i-cells, which help the jellyfish sense and interact with food; and the stinging nematocyst cells. Undifferentiated cells showed a tendency to transform into epithelial cells because those are the most common cells in a fully developed tentacle.
Blastema formation in jellyfish:
Most of the cells forming the blastema are not stem cells from the base migrating to the tip. However, there is still a role for stem cells at the base. The team believes that these cells assist in the growth of the new tentacle from the base, adding some length while the proliferating cells lengthen from the tip. Removing the stem cells at the base will also delay the formation of the blastema by a week or two.
Jellyfish regeneration and bilaterians:
Overall, it was found that blastema formation in jellyfish is very similar to that in bilaterians capable of regeneration. However, it remains unclear exactly how and where the proliferating cells are formed. Researchers believe it is possible that these cells are derived from already differentiated cells that are mobilizing to form the blastema. Examples of differentiated cells transforming into blastema have been seen in starfish and grasshoppers.
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Could humans be capable of regeneration?
This could happen. Some experiments on animals that do not regenerate naturally have successfully regrown tissues. With a better understanding of the mechanisms behind this phenomenon, human treatments utilizing regenerative processes may someday be developed, but for now, that remains in the realm of science fiction.
Source: PLOS Biology, 2023. DOI: 10.1371/journal.pbio.3002435
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Author: Elizabeth Rayne. Elizabeth Rayne is a writer who covers living organisms. Her work has appeared in SYFY WIRE, Space.com, Live Science, Grunge, Den of Geek, and Forbidden Futures. She lurks outside New York City with her parrot, Lestat. When she’s not writing, she’s either shape-shifting, painting, or dressing up as an unheard-of character. Follow her on Threads and Instagram @quothravenrayne.
Source: Ars Technica
Source: https://arstechnica.com/science/2024/01/jellyfish-regenerate-lost-tentacles-and-now-we-know-how/
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