Two Became One

Synchronized contractions when poked (Nature gif)

Two comb jellies merged into a single organism in a Massachusetts lab:

In a strange episode in the animal kingdom, a captive marine animal merged with another of its kind to become a single individual.

The organisms that merged are comb jellies, translucent invertebrates that resemble jellyfish but belong to a different group of marine animals called ctenophores. They grow to about 4 inches long by 2 inches wide, eat plankton and are found throughout the northern and southern Atlantic Ocean.

Marine scientists discovered the merger when one comb jelly went missing from a laboratory tank, while another appeared unusually large. After taking a closer look, the researchers found that the big one was two individuals now sharing digestive and nervous systems...

The researchers fed the combined comb jellies fluorescent brine shrimp and watched as the bits of food made their way through their shared digestive system.

[Postdoctoral researcher Kei] Jokura speculated that the animals—also known as sea walnuts—sustained minor injuries in the tank, which activated the merger process. To prove this, he and colleagues put 10 pairs of injured comb jellies near each other. Nine of the 10 pairs successfully fused together.

“In just about two hours, their muscle contractions became synchronous in functional fusion,” he said. “It was remarkable and incredible.”

This discovery has possible implications for human health. Just as in the case of anglerfish sexual parasitism, the sea creatures lose the sense of self that distinguishes foreign tissue from their own. Overcoming this normally valuable protective mechanism is crucial to prevent rejection in transplant surgery.