The ocean can be deep and dark. While some parts can be over 5000 metres deep, sunlight can only reach around 200 metres – this means deep sea animals have had to adapt to living in darkness.
Bioluminescence is the ability for a living thing to create light through a chemical reaction. The chemical luciferin and a protein called luciferase react, with some oxygen, to produce light. This light can be a range of colours, but most light emitted by marine animals is blue or green and lasts for a short amount of time.
This ability can be used in a number of ways, so here are 5 ocean animals that use bioluminescence and why:
Anglerfish
When we talk about bioluminescent marine animals, an anglerfish is probably the most recognisable. However, did you know only female anglerfish use bioluminescence and that they have to rely on bacteria to help them produce their lights. Small bacteria (Photobacterium) live in the anglerfish’s lures and the fish use the light to attract prey.
Credit: Wikimedia / Brauer
Lanternfish
Lanternfish use light-emitting organs called photophores to protect themselves from predators. While the layout of their photophores can vary, they are usually found on their undersides creating a type of camouflage known as counterillumination. With counterillumination, the light from the photophores helps hide the fish’s silhouettes from predators below.
Credit: Wikimedia / Emma Kissling
Sea jellies
Lots of sea jellies use bioluminescence, but the deep-sea Atolla jellyfish has a pretty cool technique. When attacked, this animal will create a sudden flash of lights known as a ‘burglar alarm’. The lights draw the attention of larger predators, which will hopefully come and attack whatever was threatening the Atolla.
Credit: Wikimedia / NOAA’s Fisheries Collection
Heterocarpus shrimp
Heterocarpus is a genus of deep sea shrimp and a number of these species use bioluminescence as a defence mechanism. They have been seen ‘vomiting’ up bioluminescent fluid from glands near their mouths when threatened, helping them escape.
Credit: Wikimedia / Corbari L.
Worms
The green bomber worm (Swima bombiviridis) is found in the deep ocean and gets its name from their green, bioluminescent sacs. When threatened, these worms detach their glowing sacs, which look like green bombs, to distract their predators. The sacs grow back so this worm can escape from future threats.
Credit: EurekAlert / Casey Dunn
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