Scientists Unravel Mystery of the Jellyfish's 'Superpower' Ability to Regenerate Body Parts

Scientists have unraveled the biological mechanisms behind what they describe as the extraordinary "superpower" ability of jellyfish to regenerate body parts.

Jellyfish are primitive animals which evolved in the oceans around 600 million years ago. Part of the reason for their evolutionary success is that some species are able to grow back tissue that has been lost—a trait that is rare in the animal kingdom.

To learn more about this poorly understood ability, a team of researchers from Tohoku University in Japan investigated the biology of a jellyfish species known as Cladonema pacificum—which has tentacles that spread out like tree branches—for a study published in the journal PeerJ.

"Currently our knowledge of biology is quite limited because most studies have been performed using so-called model animals like mice, flies, worms and fish etc. Given that millions of species exist on the earth, it is important to study various animals and broaden our knowledge," Yuichiro Nakajima, an author of the study from the Frontier Research Institute for Interdisciplinary Sciences at Tohoku, said in a statement.

"Jellyfish are one of such animals with interesting biological features," Nakajima said. "For example, they have stinging cells, called cnidocytes, to capture prey."

In their research, the Tohoku scientists investigated how cells proliferated in the jellyfish during their various developmental stages. Cladonema pacificum was a suitable subject to study these processes because it is easy to maintain in a lab and has a high spawn rate.

Specifically, the team examined the distribution of special proliferating cells—which are important for cell division—in the body of the jellyfish and how the animal's intake of food could influence its body-size, shape and regenerative abilities. Cell division is a process which involves a "parent" cell producing two identical clone cells.

The team's research showed that during the so-called "medusa" phase of the jellyfish's lifecycle, these cells were distributed across the animal's body in different patterns.

The medusa phase is the stage of jellyfish development that is perhaps most familiar to us because this is usually when the animal swims around and has tentacles hanging down from the umbrella-shaped main body. During this phase, male and female medusae reproduce.

In their study, the Tohoku team noticed that proliferating cells in C. pacificum medusae were spread out uniformly in the umbrella-shaped body part, while in the tentacles they were collected in distinct clusters.

When the researchers took food away from the jellyfish or blocked cell proliferation from occurring using a special substance, they found that the animals grew to smaller sizes. Furthermore, this also caused caused defects in how the tentacles branched out during development, as well problems with regeneration.

These results indicate that the proliferating cells are key to determining the body size, tentacle shape and regenerative abilities of the jellyfish during their sexual phase, according to the researchers.

"We are currently trying to understand the molecular mechanisms of Cladonema development and regeneration," Sosuke Fujita, another author of the study, said in the statement. "Based on this research, molecular control of cell proliferation is the key to deciphering jellyfish growth and regeneration."

Cladonema jellyfish
Cladonema jellyfish have branched tentacles. Sosuke Fujita, Tohoku University