The term “bioluminescence” refers to a living organism’s ability to produce and emit light. It is one of the most fascinating and intriguing phenomena in nature.
The tendency of animals to emit light is not completely limited to creatures swimming in the dim and dark depths of the ocean. However, the vast majority of bioluminescent animals are found in the sea. On the other hand, there is only a handful of bioluminescent land animals, most notably the firefly and the glow worm.
These glow-in-the-dark creatures continue to fascinate human observers. But for the animals, they use bioluminescence as part of their survival – a strategy to lure prey, a way to attract mates or a defense mechanism to bewilder their predators.
Without further ado, here are some of the amazing animals known for their bioluminescence:
Probably the best-known bioluminescent land creature, a firefly is a winged beetle which has specialized light organs emitting from its abdomen. The light is due to a reaction of luciferin (a chemical which is also found in other bioluminescent insects) together with calcium, oxygen, adenosine triphosphate (ATP) and an enzyme called luciferase.
There are over 2000 species of fireflies, which are found in both temperate and tropical environments. Fireflies produce light of various colors such as white, yellow, green, or pale red. They emit light in blinking patterns to attract mates, or to warn predators not to eat them because their bodies contain toxic chemicals which deem unappetizing.
Despite the name and appearance, a glowworm is not a worm at all, but a larva of various insect groups, as well as adult females resembling a larva. They produce light of different colors such as green, orange, and yellow. Many of these glowworms belong to the four families of beetles: Elateridae, Lampyridae, Phengodidae, and Rhagophthalmidae.
The adult females that resemble an insect in a larval stage are called “larviform females.” Usually, larviform females are wingless and larger than males.
Like fireflies, glowworms also produce light from their abdomen. Glowworms emit light to attract prey, as well as to warn predators that they are toxic and would not make a tasty meal.
3. Clusterwink snail
When disturbed, the clusterwink snail flickers its shell with a bluish-green light, which becomes more intense when it encounters an impact with a fast-moving object. The light may function as a defense mechanism to dazzle and confuse predators, while the soft parts of the snail’s body remain protected by its shell. As the light stuns its predator, it even attracts the larger predators of the snail’s predator.
The jellyfish is another well-known bioluminescent creature. Many of the jellyfish species emit blue or green light from their transparent bodies, displaying one of the most dazzling and beautiful scenes in the underwater. Like many other bioluminescent animals, the jellyfish uses its light for defensive purposes. The light emission is activated upon contact, which serves to stun predators. The light also makes the predators more vulnerable and may attract other creatures to prey on the jellyfish’s predators.
5. Sea sapphire
The Sapphirina or sea sapphire belongs to the group of small crustaceans called copepods. This tiny and translucent parasitic creature is found in the marine environment all over the world. While other bioluminescent creatures glow, the sea sapphire otherwise sparkles. This is partly due to its iridescent, crystal plates inside the animal’s epidermal cells which can capture light and reflect it back. The light may come in different colors such as blue, yellow, orange, and gold.
Males only emit light in the presence of females as a way to attract them. They light up, and within the blink of an eye, they disappear.
6. Firefly squid
The firefly squid is only one of the few squids that display bioluminescence. Its head, arms and mantles have tiny light-producing dots called photophores. The squid flashes its light as a way to lure prey, mainly small fish. The light emission also serves to attract a mate.
Firefly squids have been long observed in Japan to give a mesmerizing marine light show. The county has long considered firefly squids as a delicacy.
The dragonfish is a monstrous-looking scaleless fish that belongs to the group Stomiidae. They have specialized organs called photophores, which are responsible for emitting light. Like many bioluminescent marine creatures, the dragon is typically found in the depths of the ocean. Dragonfish uses its light to lure prey. Aside from the blue-green light, the dragonfish has also the ability to emit red light, which serves to locate prey in the dark.
Dinoflagellates are also known as “fire algae,” a type of unicellular algae. These tiny creatures are found in both seawater and freshwater environments. Some species of dinoflagellates have the ability to emit light due to the chemical compounds that produce light as they react to external stimuli. The dropping temperatures also cause dinoflagellates to glow. While their displays of light during the night continue to dazzle spectators, dinoflagellates use their unique incandescent feature to ward off prey.
A few species of octopus are bioluminescent, most notably the glowing sucker octopus. Its tentacles have photophores, which are responsible for emitting light. The flashes of light serve to attract prey, to ward off predators, as well as to attract mates.
10. Cookiecutter shark
The cookiecutter shark is one of the few sharks which prefer to live in the depths of the ocean. It gets its name from its curious way of feeding: it gouges out round, cookie-sized chunks of flesh of its hapless victims. It has a dark brown body and an even darker “collar” in the gill region, which is believed to act as a lure.
The cookiecutter shark’s lower belly is concentrated with photophore glands, which are responsible for producing light. These glands produce luciferase, an enzyme also found in other bioluminescent creatures. Luciferase converts chemical energy to light energy, causing it to emit light. The gland’s surrounding transparent cells also allow the light to glow throughout the cookiecutter shark’s skin.