In a Frankenstein-y feat, a small, gelatinous sea creature can merge its physique with a neighbor’s. The animals — known as sea walnuts, a kind of comb jelly — can then sync up their bodily features, researchers report October 7 in Present Biology.

Biologist Kei Jokura first found the mashup when he discovered an unusually massive sea walnut (Mnemiopsis leidyi) floating in a set tank. Turned out, it was truly two jellies joined collectively.

Jokura, who did this work whereas on the Marine Organic Laboratory in Woods Gap, Mass., suspected that they had develop into injured within the assortment course of and, attributable to tight quarters, fused their our bodies whereas therapeutic. Comb jellies are recognized for his or her capability to regenerate components of their very own physique, however the sight of two hooked up sparked Jokura’s curiosity.

“At first, I used to be very shocked,” says Jokura, now on the Nationwide Institutes of Pure Sciences in Okazaki, Japan. Then he thought, “Let’s attempt to reproduce this beneath the microscope.”

Jokura and colleagues took pairs of comb jellies, trimmed off a bit from every of them and pinned them to dissection dishes with their lower ends abutting. In 9 out of the ten pairings, the harm websites fused in a single day, making a steady stretch of tissue.

They didn’t simply appear like one organism — they acted like one additionally. When prodded on one aspect of the twin jelly, each our bodies responded by contracting. That means the jellies’ nervous methods may also have fused, the authors say (SN: 4/20/23). And each our bodies circulated meals between them, regardless of the group feeding just one mouth of the duo.

As a result of comb jellies are unfold out within the open ocean, fusion most likely occurs solely in a lab setting, says Steven Haddock, a marine biologist on the Monterey Bay Aquarium Analysis Institute in Moss Touchdown, Calif. In his personal work with comb jellies, he’s seen one other species, the ocean gooseberry (Pleurobrachia pileus), fuse after assortment, however not in a synchronized method. “Nothing like this, the place they’re coordinating their reactions,” he says. “It’s fairly outstanding.”

The ocean walnuts’ fusion prowess means that the animals lack the power to tell apart between their physique and one other physique, a trait known as allorecognition. In people, allorecognition is what may cause the physique to reject organ transplants. Comb jellies are one of many oldest lineages of animals, which suggests the absence of allorecognition in sea walnuts may maintain clues for the way the trait developed (SN: 12/12/13). However to grasp that, Jokura says, extra analysis must be completed on their neurology and the genes accountable.