Comb Jellies Can Fuse Together to Form One Individual

Biologist Kei Jokura probably did a double take followed by a cartoonish rub of his eyes with his fists when, in the summer of 2023, at the Woods Hole Oceanographic Institution in Massachusetts, he observed a pair of ocean-dwelling invertebrate blobs called comb jellies fuse to become a single organism.

The jellies didn’t just fuse their bodies. They fused their nervous and digestive systems as well. According to the findings Jokura co-authored with researcher Mariana Rodriguez-Santiago and published in the journal Current Biology, two creatures fully became one.

Comb jellies are among the oldest living animals on earth. Their unique physiology makes them perfect for studying the origins of complex nervous systems. In doing so, we can better understand the basic function of the nervous system and overall adaptability.

Their discovery not only challenges preconceived notions of the comb jelly’s capabilities but also challenges more philosophical questions of self and non-self. Are the jellies still individuals? Are they a single entity? The jellies can’t talk to give us its pronouns but would it identify as They/Them if it could?

The fusion breaks several long-established rules of biology. The bodies of most animals can distinguish their own cells from foreign ones, which is why organ transplants sometimes fail after the host body rejects its new resident. The comb jellies seem to lack this mechanism, allowing them to merge without a negative immune reaction.

Jokura and Rodriguez-Santiago were studying injured specimens when the initial fusion occurred. They decided to re-create the conditions by slicing off parts of a bunch of jellies and then putting them together in petri dishes to see what would happen. The next day, they found that nine out of the 10 pairs they put together had fused.

Now, while typical jellies usually have only one set of sensory organs or one anal opening, they were fused as one entity with two of each. Food would enter one jelly’s mouth then move through the shared digestive tract and finally be expelled by both organisms.

There’s still so much more to learn about comb jellies and their newly discovered ability to fuse. Jokura says he wants to look into how fused jellies think, saying, “I would like to investigate how their ‘thoughts’ are integrated.” These simple yet immensely complicated blobs of life might be a key to understanding the fusion of consciousnesses.