Deep-sea Jelly Glows Blood-red to Hide in Blackness of the Twilight Zone

A bizarre jelly creature that lives in the deep sea has a belly that glows blood-red, which helps it to avoid predators.

The aptly named bloody-belly comb jelly (Lampocteis cruentiventer) has been spotted in waters ranging from 984 to 9,842 feet deep, with most observations occurring at depths of around 1,640 feet, George Matsumoto, a senior education and research specialist, at the Monterey Bay Aquarium Research Institute (MBARI) in California, told Newsweek.

This species is found throughout the Pacific Ocean basin and has been seen in the Atlantic Ocean basin as well. "We see them on most of our ROV [remotely operated underwater vehicle] dives so I would say that they are relatively common in the Eastern Pacific," Matsumoto said.

Comb jellies are a group of marine invertebrates technically known as ctenophores that are not true jellyfish despite their resemblance to these creatures.

All comb jellies have eight bands or rows of tiny hair-like structures called cilia, which beat continuously, propelling the animal through the water. When light strikes these bands of moving cilia, it diffracts and refracts in such a way that it produces a shimmering rainbow of colors.

Ctenophores lack the stinging cells that are characteristic of the group of animals called Cnidaria—which includes true jellyfish and corals, along others—and have the largest cilia known to science.

The bloody-belly comb jelly is somewhat unique, according to Matsumoto, because it represents an entirely new family and genus (group of species) of ctenophore.

"They are gorgeous—but that is in the eye of the beholder and I might be a little biased," said the researcher, who was part of a team of scientists that first described the species around 20 years ago.

"It is likely that there are more species in this genus as we have been seeing some diversity in coloration and canal structure."

The diet of the bloody-belly comb jelly, which can grow to a maximum size of around 6 inches, is not very well-studied. But scientists do know that many of the deep-sea creatures this relatively primitive animal eats are capable of bioluminescence, or in other words, creating their own light.

Researchers think the glowing red belly that gives this species its name may help to mask any bioluminescent light from the prey it consumes, which could attract unwanted attention from predators.

While it may seem like a glowing red belly might not be such a good idea if you are trying to stay hidden, there is a reason behind the evolution of this trait. Red is the first wavelength of light absorbed as you descend into the deep sea. So in these regions, bloody-belly comb jellies appear black, rendering them virtually invisible given the darkness of their surroundings.

The overall color of this animal can vary from transparent to amber and deep red. But the belly is always blood-red in order to conceal from predators whatever prey may be within.

Staff at MBARI have been learning to care for these jellies and the institute is the first aquarium to exhibit these strange creatures in the United States. This has been a challenge because they are "incredibly fragile" and sensitive to temperature and oxygen levels, according to Matsumoto.

"The fact that the Aquarium has been able to display them in captivity is truly exceptional," he said.

While it may seem like the deep-sea habitat of these animals is somewhat shielded from the impacts of human activity, this is not necessarily the case, Matsumoto said.

"Since they are sensitive to changes in temperature and oxygen, the warming ocean and the change in oxygen as a result of climate change are going to change the distribution of the lovely and amazing ctenophore."

"We do not yet know what changes in pH will have as the ocean becomes more acidic but our hypothesis is that it will not be beneficial to the ctenophore. I hope that by bringing these animals to the public and making them aware of some of the denizens of the deep and how sensitive ocean organisms are to climate change will help inspire behavioral changes to help reduce [its] impacts."