Two injured individuals of Mnemiopsis leidyi, a species of planktonic animals known as comb jellies or ctenophores, are capable of rapidly fusing into a single entity in which some physiological functions are integrated, according to new research.
While maintaining a population of Mnemiopsis leidyi in a seawater tank, Jokura et al. noticed an atypically large individual with two aboral ends and two apical organs. Image credit: Jokura et al., doi: 10.1016/j.cub.2024.07.084.
“Our findings suggest that ctenophores may lack a system for allorecognition, which is the ability to distinguish between self and others,” said Dr. Kei Jokura, a researcher at the University of Exeter and the Japan’s National Institutes.
“Additionally, the data imply that two separate individuals can rapidly merge their nervous systems and share action potentials.”
Dr. Jokura and colleagues made the observation after keeping a population of Mnemiopsis leidyi (also known as the sea walnut) in a seawater tank in the lab.
They noticed an unusually large individual that seemed to have two backends and two sensory structures known as apical organs instead of one.
They wondered if this unusual individual arose from the fusion of two injured jellies.
To find out, they removed partial lobes from other individuals and placed them close together in pairs. It turned out that, 9 out of 10 times, it worked.
The injured individuals became one, surviving for at least 3 weeks.
Further study showed that after a single night, the two original individuals seamlessly became one with no apparent separation between them.
When the researchers poked at one lobe, the whole fused body reacted with a prominent startle response, suggesting that their nervous systems also were fully fused.
“We were astonished to observe that mechanical stimulation applied to one side of the fused ctenophore resulted in a synchronized muscle contraction on the other side,” Dr. Jokura said.
More detailed observations showed that the fused comb jellies had spontaneous movements for the first hour.
After that, the timing of contractions on each lobe started to synch up more.
After just two hours, 95% of the fused animal’s muscle contractions were completely synchronous.
They also looked closely at the digestive tract to find that it also had fused.
When one of the mouths ingested fluorescently labeled brine shrimp, the food particles worked their way through the fused canal.
Eventually, the comb jelly expelled waste products from both anuses, although not at the same time.
“It remains unclear how the fusion of two individuals into one functions as a survival strategy,” the authors said.
“Future studies will help to fill the gaps in understanding, with potential implications for regenerative research.”
“The allorecognition mechanisms are related to the immune system, and the fusion of nervous systems is closely linked to research on regeneration.”
“Unraveling the molecular mechanisms underlying this fusion could advance these crucial research areas.”
The study appears in today’s issue of the journal Current Biology.
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Kei Jokura et al. 2024. Rapid physiological integration of fused ctenophores. Current Biology 34 (19): 889-890; doi: 10.1016/j.cub.2024.07.084
Source : Breaking Science News