Three quarters of deep-sea animals make their own light

Date: April 10, 2017

Source: Monterey Bay Aquarium Research Institute

Ever since explorer William Beebe descended into the depths in a metal sphere in the 1930s, marine biologists have been astounded by the number and diversity of glowing animals in the ocean. Yet few studies have actually documented the numbers of glowing animals at different depths. In a new study in Scientific Reports, MBARI researchers Séverine Martini and Steve Haddock show that three quarters of the animals in Monterey Bay waters between the surface and 4,000 meters deep can produce their own light.

You would think it would be easy to count the number of glowing (bioluminescent) animals in the ocean, just by looking at videos or photographs taken at different depths. Unfortunately, very few cameras are sensitive enough to show the pale glow of many marine animals. Below 300 meters (1,000 feet) the ocean is essentially pitch black, so animals don't need to glow very brightly. Also most animals don't glow continuously because making light takes extra energy and can attract predators.

Because of the difficulty in counting glowing animals at depth, most previous estimates of the proportion of glowing animals were based on qualitative observations made by researchers peering out the windows of submersibles. Martini and Haddock's study is the first ever quantitative analysis of the numbers and types of individual glowing animals at different depths.

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How the Hairy-Chested 'Hoff' Crab Evolved

Yeti crabs don't comb their hair to look good — they do it because they're hungry.

These bizarre deep-sea animals grow their food in their own hair, trapping bacteria and letting it flourish there before "combing" it out and slurping it up. The crabs are found near cold seeps and hydrothermal vents, places where mineral-rich water spews out of the seafloor.

Like many animals that live in these extreme environments, yeti crabs have been thought of as "living fossils," largely isolated from the rest of world and, therefore, unchanged for eons. But new research shows these animals actually evolved relatively recently, suggesting the deep-sea environments the crabs call home may be more changeable than previously thought and more vulnerable to shifts in the atmosphere and climate, said Oxford University researcher Nicolai Roterman. 

A study by Roterman and his colleagues detailing the evolutionary history of these bizarre creatures was published today (June 18) in the journal Proceedings of the Royal Society B, and their research turned up a few surprises.

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