Hatchetfish

Hatchetfish: 

The series Blue Planet featured a segment on the deep sea. The film focused on how fish use bioluminescence, navigate within the twilight zone and the deep abyss, and find food and mates when resources are limited. The film also featured hatchetfish, which are very interesting creatures.

Hatchetfish belong to the family Sternoptychidae. Forty-five known species of Hatchetfish have been discovered thus far. The size of the species varies but on average, the Hatchetfish is no bigger than 10 centimeters. They can be found in warm temperate waters at depths of 200 to 1000 meters.

The Hatchetfish received its name because their body shape is similar to that of a hatchet. The body of the Hatchetfish is flat and compressed with shiny mirror-like sides. The mirror-like sides manipulate light particles that have reached the depths. The reflected light makes the Hatchetfish disappear in the deep abyss by making it appear dark in coloration.

The eyes of the Hatchetfish face upward so that glimpse of light can be utilized to find potential prey items like plankton and crustaceans. The technique the Hatchetfish employ to find food is similar to techniques exploited by its predators. Hatchetfish have photophores and bioluminescent organs that line the ventral side of its body in order to defend themselves from predators looking up at their silhouette. The photophores contain a chemical called luciferin that produces ultraviolet light. The light produced breaks up the silhouette of the Hatchetfish by making the ventral side have a similar brightness to the light particles that have reached the depths. The Hatchetfish is able to control the amount of light given off by its body depending on the amount of light being emitted by the environment around it. This technique is called counter illumination.

The Hatchetfish uses strategies such as a mirror like bodies, counter illumination in order to remain concealed from predators, and had large eyes that face upward in order to find prey. These strategies have allowed the Hatchetfish to survive in the deep-sea.

Work Cited
"BBC - Science & Nature - Sea Life - Fact Files." BBC - Homepage. Web. 15 Sept. 2012. < http://www.bbc.co.uk/nature/blueplanet/factfiles/fish/hatchetfish_bg.shtml>.
Mensinger, A.F. "THE SKIN | Bioluminescence in Fishes." ScienceDirect. Ezproxy, 2011. Web. 15 Sept. 2012. <http://www.sciencedirect.com.ezproxy.stockton.edu:2048/science/article/pii/B978012374553800160X>.