The deep sea hatchetfish gets its name from the distinct hatchet-like shape of its body. It is a member of the Sternoptychidae family of deep sea fishes. There are about 45 individual species of hatchetfish that vary in size from one to six inches. They are most well known for their extremely thin bodies which really do resemble the blade of a hatchet. They should not be confused with the freshwater hatchetfish commonly seen in home aquariums.
Of the several species of hatchetfish that inhabit the ocean depths, the largest is Argyropelecus gigas, also known as the giant or large hatchetfish. This giant of the family grows to an impressive six inches (12 centimeters) in length. Most of the smaller hatchetfish species are covered in delicate silvery scales. Some species, including the giant hatchetfish can be brown or dark green in color. Hatchetfishes have large, tubular eyes that pointing upward. This enables them to search for food falling from the above. Because there is very little light at the great depths at which they are found, their eyes have become extremely sensitive to light and are good at distinguishing shadows against the extremely faint illumination from above.