The fangtooth, or Anoplogaster cornut, is one of the deepest-dwelling ocean fish, living as far down as 16,000 feet (5,000 m). Also known as the ogrefish, the shorthorn sabretooth, and the devil berycoid, this ferocious-looking fish gets its name from its disproportionately large jaw and needle-sharp teeth. The lower teeth of the fangtooth are so large that it has developed specialized pockets within the mouth to enable it to close its jaws. In spite of its oversized fangs, the fangtooth is a small fish, typically reaching 6 inches (16 cm) in length.
Fangtooths generally inhabit ocean depths of from 1,640 to 16,400 feet (500 to 5,000 m). This small fish has been known to ascend to the near surface to feed at night, but always returns to the lower depths during the day. The fangtooth has tiny eyes and poor vision and is thought to hunt by its sense of touch. It has a ridge along its spine that heightens sensitivity to its surroundings.
The fish lives in temperate and tropical oceans, primarily the Pacific, Atlantic, and Indian Oceans. It has adapted to living in near freezing water far below the surface. Larger predatory fish such as tuna and marlin feed on the fangtooth, though usually only when the fangtooth ventures too near the ocean surface.
The breeding season for this deep sea fish is June through August. After hatching, the larvae appear similar to plankton. Unlike the adult, the juvenile has spikes on its head, a swim bladder for buoyancy, and temporary gill rakes that filter in the aquatic organisms the young fish feed on. At about 3 inches (7.6 cm) in length, the young fish becomes a mature adult and loses its head spikes and gill rakes. The swim bladder diminishes in the adult to allow the fangtooth to descend further down into the sea. As adults, fangtooths eat small fish and crustaceans such as shrimp. This spike-toothed fish often eats other fish nearly one-third the size of its own body.
Scientists have gathered relatively little information about the fangtooth fish. Before 1955, researchers believed the juvenile to be a different species from the adult because of its strikingly different appearance and habitat. The greatest difference between juveniles and adults is the former's single row of ordinary-looking teeth as compared to the adult's oversized fangs. Juveniles habitually inhabit surface waters, while adults typically live in the deep sea.