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Comb jellies make their own glowing compounds instead of relying on food

At least two comb jelly species are able to produce coelenterazine, an essential bioluminescent compound, on their own, according to new research. Photo by William Browne
At least two comb jelly species are able to produce coelenterazine, an essential bioluminescent compound, on their own, according to new research. Photo by William Browne

Dec. 11 (UPI) -- Comb jellies don't have to rely on their food to acquire coelenterazine, the light-emitting compound that helps many deep sea species hunt for prey, woo mates and communicate with rival and peers.

According to a new study, published this week in the journal iScience, at least two species of comb jellies are capable of synthesizing their own.

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In the deep sea, light is at a premium. Without the help of the sun, animals must produce their own. But while dozens of deep sea species -- from jellies and brittle stars to squids and fish -- utilize the light-emitting chemical coelenterazine, most acquire the compound by eating other animals.

Because coelenterazine reacts only once to produce light, it must be continuously replenished. Until now, scientists had only found two species that make their own, the open-ocean copepod Metridia pacifica and the deep-sea shrimp Systellaspis debilis.

Unfortunately, copepods and deep-sea shrimp are quite difficult to study. As a result, their coelenterazine-production methods remain a mystery.

For the newest study, researchers were able to breed the two comb jelly species, Bolinopsis infundibulum and Mnemiopsis leidyi, in captivity, feeding them only coelenterazine-free species.

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Nevertheless, the comb jellies kept on glowing, and the team of scientists -- led by Manabu Bessho-Uehara, postdoctoral fellow at the Monterey Bay Aquarium Research Institute -- were able to detect coelenterazine in their bodies.

"Manabu's experiments gave some of the clearest and most compelling results of any research that I've been involved with," study co-author Steve Haddock, MBARI marine biologist, said in a news release.

By comparing the lineages of comb jellies, copepods and deep-sea shrimp, researchers confirmed the three groups evolved their coelenterazine-production capabilities independently.

The research team has already sequenced the genome of one of the comb jellies, and they hope genetic analysis will help them better understand the genes and biochemical mechanics that underpin the ability to make coelenterazine.

"We really want to figure out the genes involved in making this molecule," said Haddock. "It would tell us so much about the evolution of bioluminescence, and could usher in a new generation of biotech tools. Turning these fragile jellies into 'lab rats' has enabled experiments that we could never have done a few years ago. I am hopeful this will be the key to solving the mysterious origins of bioluminescence."

Eventually, scientists hope to use what they learn from the comb jellies' coelenterazine-production techniques to synthesize new kinds of bioluminescence compounds -- compounds that could be used for biomedical, biochemical and genomic research.

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"The building blocks of coelenterazine are some of the same amino acids that are found in all living organisms, including humans," said Bessho-Uehara.

"If we can introduce the genes that produce coelenterazine into living cells of other organisms, we can make parts of these cells glow. This would help us understand how the cells behave, develop, and respond to changing conditions. Such technology would light up the life sciences by overcoming some of the difficulties that we have with current glowing compounds," Bessho-Uehara said.

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