Comb jellyfish, specifically the Mnemiopsis leidyi species (also known as the warty comb jelly), exhibit an extraordinary ability to fuse together after injury, merging not only their outer tissues but also their nervous and digestive systems. This remarkable finding by biologists at the University of Chicago’s Marine Biological Laboratory could have significant implications for regenerative medicine.
The initial discovery was serendipitous. Researchers observed a comb jelly with two apical organs (sensory organs common in invertebrates) and two aboral ends, suggesting a fusion of two individuals. This led to the hypothesis that the jellyfish had merged to survive injuries.
To test this, the researchers partially amputated lobes from healthy comb jellies and placed them together. In nine out of ten cases, the pairs fused into a single entity, surviving for the entire three-week experimental period, as reported in Current Biology.
The fusion process was rapid. Within an hour, the grafted lobes synchronized their movements, reaching 95% synchronization within two hours. Overnight, the boundary between the jellyfish became seamless, and even their nervous systems showed signs of integration. Stimulating one side of the fused jellyfish triggered a response on the other side, a surprising observation noted by postdoctoral researcher Kei Jokura.
The digestive system also functioned as a unit. Fluorescently-labeled brine shrimp injected into one side of a fused jellyfish were digested, and fluorescent particles moved into the attached individual’s lobe, which subsequently expelled waste. This suggests a functional coupling of the digestive systems. However, the independent waste expulsion from each side implies the two jellyfish don’t fully integrate into a single organism.
Further research is needed to understand the mechanisms behind this fusion, especially how the nervous systems combine. This discovery extends beyond a unique survival mechanism. The jellyfish seemingly lack allorecognition, the ability to distinguish self from non-self cells. This has implications for organ transplantation and could lead to advancements in immune system and regenerative therapies.
