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Stoplight Loosejaw

Malacosteus niger
Stoplight Loosejaw is the common name for the two species found within the genus Malacosteus. They are a relatively deep-sea dwelling fish, living between 500 and 1,000m down.

The "Stoplight" name derives from the fact that they can produce two different lights from photophores near their eyes. One of these lights is blueish-green, while the other is red. The red light is especially interesting-- most of the other organisms near them cannot see the red light, which lets the Loosejaw hunt secretly and stealthily. (The blue light penetrates further in the water, but can be seen by others).

The "Loosejaw" name is a reference to their interested head. They have a very minimal connection between their head and neck, and can tilt their heads back at normally unnatural angles in order to thrust their long, lower jaws even further forward. These lower jaws have very sharp, pointed teeth that impale prey, after locating it and swiftly darting forward in attack.

Like many deep sea fish, we don't know much about the specific behaviors of the Stoplight Loosejaw. In fact, most of what we know about them comes from dead specimens. Next to nothing is known about their reproduction, but there is some speculation that the lights play a part in courtship.

IUCN Status : Not Listed
Location : Oceans Worldwide
Size : Length around 25cm
Classification : Phylum : Chordata -- Class : Actinopterygii -- Order : Stomiiformes
Family : Stomiidae -- Genus : Malacosteus


  1. Thank you for making this page! It was very useful in a research project that I'm doing.


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