Strange Animals that Glow in the Dark

Did you know that hummingbirds can fly backwards? Or that a cockroach can survive for a week, without its head? Animals have amazing physical and biological abilities. One of the freakiest is their ability to produce their own light. This amazing animal ability is called bioluminescence. It is a bio-chemical reaction between enzymes and a light-producing substance, taking place within the organism's body in an organ known as a photophore. This form of light is interesting energy-wise, as no heat or radiation is produced during its creation and its emission. Which are the animals that glow in the dark? Many marine species, especially deep-sea dwellers, exhibit bioluminescence. On land, it is a rarer phenomenon, present in some insects and fungi species.

Bioluminescent Animals

Anglerfish
	Scientific Name: Belongs to the Lophiiformes family
	Where Does It Live: Bottom of Atlantic and Antarctic Oceans
	Size: Between 8 inches - 3.3 feet, depending on species
	Appearance: Tiny eyes, movable filament spine in front of eyes, darkish brown or gray body color, huge head with crescent shaped mouth

The freakish "underwater monster" look of the anglerfish, is perhaps why it resides at the deepest, darkest, murkiest depths of the ocean floor, where not many fish live. The anglerfish is designed to be an ambush and stealth predator, by going "fishing" with the filament hanging from its forehead. It floats perfectly still with the light on its filament "on". The filament moves on its own, giving the appearance of a floating light in the darkness. The prey is attracted to the bright, moving light and moves towards it. Once it touches the filament, the anglerfish opens its massive jaws and snaps the prey up. Its body frame is so thin and stretchable, that it can eat prey up to two times its size.

Barbeled Dragonfish
	Scientific Name: Idiacanthus atlanticus
	Where Does It Live: Subtropical and temperate waters of the Atlantic and Southern Ocean. Resides at depths of 2000 m
	Size: 40 cm long (females), 5 cm long (males)
	Appearance: Long pointed fangs, tiny eyes, chin barbel (protruding growths from chin), black in color

This species of dragonfish exhibits a high degree of sexual dimorphism (difference in physical traits in the same species). The female (pictured above) looks like a beast from a horror movie. The male is not only smaller in size, it has no teeth, no barbel and does not hunt. It is only around for reproduction. In the dark depths of the ocean and with such small eyes, how does this predatory fish scope out its prey? By providing its own light, in the form of photophores, aligned on the side of its body and under its eyes. The fish will light up completely in the dark and glow with an eerie blue-green or reddish light. The barbel of the female also lights up at the tip. The light is powerful enough for the fish to find its prey in the dark.

Cookiecutter Shark
	Scientific Name: Isistius brasiliensis
	Where Does It Live: Warm, tropical and temperate waters in all major oceans at deep-sea depths below 3,281 feet
	Size: 42-56 cm long
	Appearance: Thin and long tube-like body, a blunt, cone-shaped snout, dark brown in color and dark collar around throat

This is the only shark species that glows in the dark. Its entire body will emit an eerie green glow, except for the dark collar. The light is so powerful, that even a dead cookiecutter shark will glow for 3 hours. A spooky green light is just one part of this shark's ghoulish appearance. Its mouth houses a large number of small but sharp triangular teeth, enclosed by suctorial lips. The lower jaw has larger, sharper teeth, as compared to the upper jaw. Gruesome jaws and bioluminescence allow the cookiecutter to feed in a rather unusual manner. Instead of preying on similarly-sized fish, it prefers to take chunks and nicks of flesh off larger fish, like tuna, other sharks and stingrays. The large fish is attracted to the shiny glow of the cookiecutter and once close enough, the cookiecutter will bite it, make a cookie-shaped hole in its flesh and let go. Such bite marks are even found on mammals like seals, dolphins and whales.

Splitfin Flashlight Fish
	Scientific Name: Anomalops katoptron
	Where Does It Live: Eastern Pacific Ocean
	Size: 9 inches
	Appearance: Solid black or light gray body color with a velvety sheen. Bluish tint on fins and tail. Large eyes with translucent flesh pockets underneath

This little fish is one of the most well-known glow-in-the-dark sea animals and is also a popular exotic aquarium fish. They belong to a family of bioluminescent fish, Anomalopidae. These fish are simple carnivores, feeding on small fish bodies like zooplankton. Why the name "flashlight fish"? The skin pockets below the eyes of the fish, are actually translucent and will glow with a white, yellow or blue light, which makes the fish look like it is smiling in the dark. These fish exhibit bioluminescence through the presence of symbiotic bacteria, present in the skin pockets. They turn the light off by rolling away the skin pocket, so the bacteria cannot be seen. The fish uses its natural light as a means of communicating with other fish, through light flashing and to attract prey. It also uses its light-producing ability to divert potential predators. As an attacker approaches the fish, it will keep the lights on and then suddenly, will turn them off and swim in the opposite direction. This confuses the predator, who is searching for the light!

Firefly/Lightning Bugs
	Scientific Name: Belongs to the Lampyridae family
	Where Does It Live: Humid, warm areas, especially in marshes or fields with long grass, near small water bodies. They are found on nearly every continent of the world.
	Size: At least 1 inch long
	Appearance: Small soft bodies, dark in color with wings and antennas

Of all the animals that glow in the dark, the firefly is easily the most famous and perhaps the smallest. This is an entire insect species, whose members all exhibit bioluminescence. Fireflies do not glow as a whole, rather the glow is emitted from their bellies. Oxygen combines with a body enzyme called luciferase, that causes the insect's abdomen to emit a light with no heat. This energy efficient glowing ability is present in both larvae and adult fireflies. Some firefly species even produce glowing eggs. Why do fireflies glow? As larvae, fireflies will glow to warn approaching predators of a bitter and sometimes poisonous taste to avoid being eaten. As adults, fireflies use light to communicate with each other and for attracting mates with blinking light flashes or continuous glowing. Depending on the species, the light patterns vary. The female of the Photuris firefly sub-species, imitates the light patterns of other fireflies, to attract males. However instead of mating with the attracted mate, this female firefly will eat it!

Vampire Squid
	Scientific Name: Vampyroteuthis infernalis
	Where Does It Live: Temperate and tropical oceanic waters, at low-light depths of 600-1,200 meters.
	Size: 1 foot or 30 cm (entire body), 6 inches or 15 cm (mantle length)
	Appearance: Two fins on the mantle, 8 arms with webbing between them, 2 filaments. 1-inch large globular eyes, either red or blue in color. Black or reddish brown body color with black underside and webbing.

The murky depths of the ocean are home to the strangest and most frightening-looking members of the animal kingdom and one such creature is the vampire squid. This squid would win a Count Dracula look-alike contest hands down, with its red ghoulish eyes and black gelatinous skin and webbing, that give it a cloak-like appearance. It seems to fly through the water, using its fins to propel itself forward at a great speed. To add to its freak factor, it has very large eyes, almost as large as a dog's, mounted on its tiny frame. The vampire squid has one more trick up its little sleeve (or arm). Its body surface is covered with photophores, so it can turn itself "off" and "on" when needed. The vampire squid has such sensitive attuned photophores, it can adjust the intensity of light and the size of the photophores, to put on a spectacular underwater light show. It will use bright blinking light to attract prey and will turn everything off and remain dark to hide from predators. If attacked, it will flash its lights to "shock and awe" the approaching predator and then squirt a thick stream of mucus from its arms, while fleeing to deter the predator.

The ability to create light from your body, or glow on your own, seems to serve a variety of purposes, from attracting a mate or distracting an attacker to having a personal flashlight. Research is being carried out into the possible use of the light-producing bacteria that causes biolumenescence, to see if it can be implanted in other animals. For now, natural body light remains an exclusive power of the animal kingdom.