Study finds that comb jellies fuse together when injured | Marine life

This may not be what the Spice Girls envisioned when they sang 2 Become 1, but scientists have found that comb jellies fuse together if they're injured.

Researchers studying a type of gelatinous marine invertebrate known as “sea nut” said they made this discovery after discovering an unusually shaped individual in a laboratory tank.

“I was very excited,” said Dr. Oscar Arenas, co-author of this work from the University of California, Berkeley.

Writing in the journal Current BiologyThe team reports that, among other features, the creature appears to have “two non-oral appendages,” or two back sides.

In addition, Arenas said, the animal had two mouths, something the team had never seen before.

“This led us to question whether this was the result of the fusion of two independent animals,” he said. “That same night, we started trying to replicate that observation.”

The team took pairs of sea walnuts — collected from different locations at different times — and removed part of the side of the body from each. Each pair was then pinned together overnight with their injuries touched.

The results revealed that in nine out of 10 cases, the individuals had integrated.

“Once we realized we could reproduce the fusion continuously, we shortened the time, and eventually found that the fusion occurred within a few hours in a petri dish,” Arenas said.

The team points out that this is not the first time grafting of comb jellies – or ctenophores – has been reported, but they say their experiments are expanding based on these observations.

Among the team's other findings was that when they prodded one side of the fused creature, both individuals shivered and shrank, a finding that suggests the pair's nervous systems may be merging, they say.

Arenas said the finding was exciting because very little is known about the ctenophore nervous system.

“Furthermore, given that ctenophores are now considered ancestral descendants of all other animals, studying how their nervous system works is crucial to understanding the basic principles of neural function,” he said.

“Beyond this, our observations suggest that ctenopods may serve as an excellent model to study the evolutionary processes of self-recognition systems and advance our understanding of tissue engraftment and regeneration in many tissues, including the nervous system.”

The idea that the two nervous systems are merging is supported by the discovery that one hour after comb-gel coupling, muscle contractions began to synchronize. An experiment involving six engaged pairs indicated that 95% of contractions within each pair were completely synchronized after two hours.

The researchers found that when they fed one comb gelatinous comb food labeled with a fluorescent label, the molecules moved into the digestive tract of the other. However, digested waste is expelled from both anuses in an asynchronous manner.

The study suggests that comb jellies have few mechanisms to distinguish their tissues from those of other species of the same species, Arenas said.

“I am convinced that it provides insight into the molecular mechanism of how single cells recognize themselves when they combine to become multicellular animals.”