About the Bristlemouth

Bristlemouths are small fish that glow in the dark and have a large mouth full of gnarly fangs. Most bristlemouths are less than 2 inches in length, smaller than your finger, but what they lack in size, they make up for in numbers. Bristlemouths are the most numerous vertebrate on Earth, with hundreds of trillions or even quadrillions swimming in the twilight zone. They are dark in color with rows of photophores along the underside that provide countershading or camouflage from predators and prey.

Bristlemouth fish haven’t always been considered the most abundant fish in the ocean. They were overshadowed by the lanternfish, quite literally. Lanternfish (myctophids) migrate up and down in the water column, ascending to follow night and food, descending to avoid light and predators. Their daily vertical migration can be tracked using sonar, bouncing off of their air-filled swim bladders. But the bristlemouth species tend to remain in the twilight zone, below 200m where they will eventually encounter food, and therefore do not need to radically adjust their buoyancy. The density of their bodies is low and instead of air, they are equipped with lipid or fat-filled bladders or no swim bladder at all.

Quick Facts

Common NameBristlemouth
Scientific NameThere are several different species, cyclothone sp. is the most common
Other NamesLongtooth anglemouth
Size2- 30cm, most are 2-3cm
DiscoveryWilliam Beebe was the first scientist to view bristlemouths in their dark habitat, in the early 1930s off Bermuda.
Eats what?Primarily of smaller fish and crustaceans
Eats how?Can open its mouth extraordinarily wide, bearing needle like fangs
Is eaten by?Predators of the bristlemouth include larger fish, such as dragon fish or fangtooths and deep diving whales
BioluminescenceYes, on the sides