Tripod fish, or Bathypterois grallatorial, are a deep sea fish that live on the ocean's floor. These fish are primarily sedentary, or remain stationary, although the fish can swim. The tripod fish is named for its appearance, as the fish has elongated pelvic fins and an elongated tail fin, which gives it the appearance that it is literally standing on a tripod.
Bathypterois grallatorial live largely in the bathypelagic zone, although some have been found in the abyssopelagic zone, of the ocean. The bathypelagic zone, which consists of the ocean layer between 3,281 feet (1,000 m) and 13,124 feet (4,000 m) below the surface, is very cold and dark, with the only light coming from animals that have bioluminescent characteristics. Water pressure can reach as much as 5,585 pounds per square inch.
The abyssopelagic zone runs between 13,124 feet (4,000 m) and 19,686 feet (6,000 m) below the surface. There is no light and the water temperature is almost freezing. Tripod fish are found in depths between 2,952 feet (900 meters) and as deep as 18,372 feet (5,600 meters) in oceans near the equator around the world.
Bodies of Bathypterois grallatorial are relatively small as the body of the largest tripod fish recorded measured 14.5 inches (37 cm). This measurement changes when the fins are taken into account. The three fins can reach 3.3 feet (1 m).
Bathypterois grallatorial stand on their fins on the floor of the ocean facing the current, waiting for food to arrive. As tripod fish have very small eyes and the water is quite dark, the fish probably depend on other senses, perhaps vibrations to their pectoral fins, which extend above the body, to know when the crustaceans that the fish consume are nearby.
Tripod fish are hermaphrodites, meaning they have both male and female sex organs. Hermaphroditic fish typically have sex organs that mature at different times. The sex organs of the tripod fish mature at the same time.
Not much is known about the reproductive behaviors and life cycles of the tripod fish. Presumably, because these fish can self-fertilize, being fertilized by another Bathypterois grallatorial may be difficult. This would indicate that there may not be a lot of genetic variations among the fish as fish who fertilize themselves would produce fry with all of the same genetic material as the parent.