Armed with the ability to accept all cells as their own, comb jellies can fuse with other … [+]
On a quiet summer day at the Marine Biological Laboratory in Woods Hole, Massachusetts, Kei Jokura, a Japanese biologist with a fascination for scallop jellies, was inspecting his latest batch. As part of his research into how these bioluminescent creatures use light to navigate, he has been studying live comb jellies in the lab.
Comb jellies are an ancient lineage of animals with a distinct evolutionary history, and despite their similar appearance, they are not closely related to true jellyfish.
Among the golf ball-sized comb jellies in his tank, he happened to notice one that stood out—a larger, strange individual with not one, but two mouths.
As Jokura and his colleague examined the strange creature, they realized that it was not a single comb jelly, but two individuals that had somehow merged into one.
What followed was an extraordinary experiment that would reveal a biological adaptation still unknown to science.
It takes 2 hours to seamlessly merge 2 “injured” Jelly Combs
After discovering the molten comb jellies, Jokura and his team set out to replicate the phenomenon. Using the styling gel type Mnemiopsis leidyi—commonly known as sea nuts—the team carefully designed experiments to understand the mechanics and implications of this fusion.
The researchers began by cutting the lobes—large, soft, and often paddle-shaped appendages—from two individual comb jellies and placing them in close proximity under controlled conditions.
After two hours passed, the two merged without a distinct boundary.
Two comb jellies with one lobe surgically removed were placed with their cut surfaces touching. with … [+]
Over the next several hours, the fused individuals synchronized their movements, and food introduced into one’s mouth traveled seamlessly through the other’s digestive system.
This fusion wasn’t just physical—it extended to their nervous systems, allowing the animals to essentially behave as one. The researchers even observed coordinated muscle contractions, further confirming the integration of their biological systems.
To verify their findings, the team repeated the experiment 10 times, different conditions to ensure robustness. They found that nine out of 10 attempts were successful.
Comb Jellies cannot distinguish between “self” and “non-self”
Scallop jellies display an unparalleled ability to incorporate foreign tissue into their own systems, effectively blurring the lines between self and non-self.
For most animals, the concept of self versus non-self is vital to survival. However, comb jelly like Mnemiopsis leidyi they function without this biological defense, making them an exception to the rule.
Allorecognition—the ability of an organism to differentiate its own tissues from those of another—is the cornerstone of multicellular life. It supports the immune system throughout the animal kingdom, allowing organisms to fend off pathogens, reject foreign tissues, and maintain bodily integrity.
Jellies’ lack of allorecognition means that they do not attack or reject foreign tissue—a feature that has played a critical role in fusion experiments performed by Kei Jokura and his team.
Scallops are adapting an alternative means of survival
The absence of allorecognition in comb jelly raises profound questions about the evolution of multicellular life.
If these ancient creatures can thrive without immune systems that distinguish self from non-self, it could challenge long-held assumptions about the necessity of such systems for survival. This could mean that allo-recognition did not evolve as a key feature of multicellularity but as a specific adaptation to certain environmental stresses or biological threats.
Additionally, comb jelly’s lack of allorecognition opens up exciting possibilities for scientific exploration. Understanding how their cells incorporate foreign tissue without rejection could lead to breakthroughs in regenerative medicine and transplantation.
Jellyfish combers stand out even in a sea full of unique creatures. Does their fascinating adaptation inspire you to seek a deeper connection with the natural world? Take a 2-minute test to find out where you stand Nature connection scale.
