Latin Name: Argyropelecus Gigas
Geographic Location: Worldwide
Depth: 300-1000 meter
Size: Up to 12 cm

The Hatchetfish Argyropelecus Gigas gets its name from their distinctive hatchet-shaped body. They are mostly silvery, latterally-flattened fishes with sharp blade-like lower bodies and a handle-like rear half of the body. Hatchetfishes have upward-directed eyes and tubular light emitting (bioluminescent) photophores. The entire underside of the body is covered by groups of large photophores. The area around the photophores is black, and the photophores are whitish grey. Light is produced in a chamber above each group of photophores and emitted from the chamber into the photophores. These tubes are silvered on the inner surface and half silvered on the outer surface. This elaborate arrangement results in the photophores on the underside of the body emitting the same colour and intensity of light as the ambient down-welling light, thus making the hatchetfish invisible to predators from below. This mimicking of light is calibrated by another pair of tiny photophores that actually point into the fishes eye therefore it can monitor the down-welling light and adjust its photophore output accordingly. They are not thought to be selective predators but rather consume anything that they can perceive, capture and swallow.