Two views of Dalatias licha, or the kitefin shark, during daylight, top, and its luminescent pattern, bottom.
Credit: © Jerome Mallefet, National Fund for Scientific Research/Catholic University of Louvain

What’s more awesome than a shark the size of a human adult? A shark the size of a human adult that also glows in the dark!

Scientists exploring the waters off the coast of New Zealand have discovered the largest glow-in-the-dark shark, the kitefin shark. The kitefin shark is not only the largest light-up shark. It is also the largest of all glowing vertebrates (creatures with a backbone) on land or sea.

The ability of a living thing to give off light is called bioluminescence. It is the result of chemical processes in living tissues. A special enzyme converts chemical energy stored in the cells into light. This process does not produce any significant heat. Most luminescent animals are found in the ocean. For example, many squids are luminescent. Fireflies are a familiar land example. Certain bacteria and fungi also are luminescent.

The kitefin is not the first shark to give off light. The lantern shark is a small shark known for producing its own light from specialized organs called photophores. These organs cover the bottom surface of the body. The light serves as a kind of camouflage (disguise), allowing the lantern shark to blend in with light filtering through the water and hide from predators (hunting animals). The light also attracts smaller animals that the lantern shark preys upon. Photophores also line the dorsal (back) spines, producing light to ward off predators.

Sharks differ from most bioluminescent animals and plants, however, because their light-producing behavior is not regulated by the nervous system. Instead, the hormone melatonin regulates their light. Did you know that you also have melatonin? But in humans, melatonin does not regulate any built-in nightlight. Instead, melatonin promotes sleepiness. Darkness stimulates the body to produce melatonin. Light blocks the production of melatonin. The hormone helps regulate the circadian rhythm, the body’s natural cycle of waking and sleeping. So, the melatonin in your body helps you drift off into a calm sleep and dream about gigantic, glow-in-the-dark sharks . . . okay, that may sound more like a nightmare.

December 12, 2016

This Monday’s monster, the viperfish, possesses one of the most frightening faces in the sea. Its colossal fangs are too large for its mouth, resting outside the mouth when it is closed. Huge, vacant eyes scan the ocean depths illuminated by its own glowing spine, while its long, skinny body creeps through the water. This frightening creature may resemble a classic sea monster, but it is not large at all, and it is no threat to humans.

The viperfish is a deep-sea fish with long fangs in its mouth. In this photograph, a viperfish stalks shrimplike prey. Credit: © Minden Pictures/Masterfile

The viperfish is a type of deep-sea fish with many long fangs in its mouth. It has a long body with black or silver skin. It can reach 14 inches (35 centimeters) long, though most viperfish are smaller. There are several species (kinds) of viperfish, all of the genus Chauliodus.

The viperfish is found throughout the world’s oceans. Most species live at depths from about 650 to 5,000 feet (200 to 1,500 meters). Some species live at even greater depths, down to more than 15,000 feet (4,600 meters).

Two of the fangs on the lower jaw of the viperfish are especially long. These fangs do not fit inside the mouth when it is closed. Instead, they fit into grooves on the head. The lower jaws of the viperfish open up to 180 degrees. Therefore, the viperfish can eat large prey, up to about a quarter of its size. The ability to eat large prey provides a great advantage in the deep sea. In this region, there is little food, and meals may be infrequent.

Viperfish live so deep in the ocean that the sun’s light is reduced to a faint glimmer, if it is visible at all. Some viperfish species swim toward the surface at night to feed. They return to deeper waters during the day. In the inky waters in which it hunts, the viperfish improves its chances of attracting a meal by producing its own light, an ability called bioluminescence. Its dorsal (back) fin has a light-producing organ at the end of a long spine. Prey animals are attracted to the light, thinking it is either a potential food source or a possible mate. When the animal gets close enough, the viperfish strikes. It will eat just about anything that can fit through its gaping jaws, including smaller fish and shrimp.

In the deep-sea realm, the viperfish is a top predator. Other animals, however, such as swordfish and tuna, dive to great depths to hunt and may consume viperfish. These much larger fish don’t seem to mind the viperfish’s terrifying appearance.