For the first time, experts observed two comb jellyfish, which are deep-sea creatures, joining their bodies when injured in the laboratory.
New research published in the journal Current Biology On October 7, it was revealed that comb jellyfish can fuse together when injured, forming a large individual with a permanently combined nervous system and stomach. Scientists accidentally discovered this in the laboratory, while doing routine research on comb jellyfish. Mnemiopsis leidyialso known as sea walnut.
Initially, the research team discovered that a test subject had disappeared from the tank. Then they noticed that one of the remaining comb jellyfish was unusually large. Upon closer inspection, they realized it was actually two individuals joined together, with no clear separation.
The team of scientists believes that this is a previously unknown adaptation, occurring because both animals were injured. To prove it, they tried to recreate the fusion process by cutting off small parts of the bodies of 20 jellyfish and then grafting them together. As a result, 9 pairs were successfully merged.
Injured jellyfish fuse quickly, often completely fusing within 24 hours of being put together. Within two hours of merging, the jellyfish pair’s nervous systems are also completely synchronized by responding to stimuli throughout their shared bodies. This rapid neural coupling likely occurs because the comb jelly’s unique neurons connect with each other in a different way than in other creatures.
The team also fed fluorescent shrimp to the fused comb jellies. Food from either of the jellyfish’s mouths moves down through both stomachs, suggesting their stomachs are also fused. However, they still have separate DNA and cannot pass on their “unique morphology” to the next generation.
Experts say this is the first case of organisms merging in this way. “To date, there have been no reports of this type of fusion in other animals,” said Kei Jokura, an evolutionary biologist at the University of Exeter who led the research team.
Previously, the fusion behavior of comb jellyfish may have gone unnoticed because it was extremely rare in the wild, Jokura added. Injured individuals must be close together to fuse, he said, and this rarely happens in the deep sea. Comb jellyfish Mnemiopsis leidyi can also recover from injury by regenerating lost body parts and reversing the aging process, making fusion with another individual less important.
The majority of fused pairs were still alive after three weeks of the experiment. However, the research had to end due to lack of funding, although Jokura thought they could survive longer. He also speculates that more than two injured jellyfish may fuse, although the team has not yet tested this.