The huge ocean is the biggest habitat of deep-sea creatures on the earth. As it is very tough to get down there, the alluring creatures are not known about much by anyone. The Monterey Bay Aquarium Research Institute (MBARI), has studied a lot of this region after observing it through videos for 17 years. These videos were located in remotely controlled vehicles on the Californian coast.

The information was collected right from the top to the bottom 3,900 meters (12,795 feet). The scientists gathered information on all the deep-sea creatures here that measured more than one centimeter, according to Mbari.

As it is very difficult to count the glowing animals at a deep level, researchers used to conduct their observations pf deep-sea creatures mainly through windows of submersible boats. As the environment is completely pitch black, scientists' cameras are not sensitive enough to capture the pale glow of the marine animals. Scientists are taking their new survey as the first ever quantitative analysis of numbers and types of glowing animals at different depths.

Scientists studied 350,000 deep-sea creatures. They were all divided into five different categories based on their bioluminescence. People are not aware of the creatures below the sea, so up to 40 percent of the species below 2,000 meters were labeled "Undefined," according to R&D.

Even though the ratio of glowing to non-glowing creatures was similar at every level, the types of light-making animals kept changing as the researchers went deeper. Hence, right from the sea surface to 1,500 meters, the glowing animals were jellyfish or comb jellies. The next level of 1,500 meters to 2,250 meters featured worms as the most abundant glowing creatures. The next level had small tadpole-like animals known as larvaceans. These were the most common deep-sea creatures.

Séverine Martini, one of the researchers, explained that bioluminescence of deep-sea creatures is not too well-known: "It's not just a few deep-sea fishes, like the angler fish. It's jellies, worms, squids...all sort of things. Given that the deep ocean is the largest habitat on Earth by volume, bioluminescence can certainly be said to be a major ecological trait on Earth," she added.

YouTube/The Science Channel