Cyclothone is a genus containing 13 extant species of bioluminescent fish, commonly known as 'bristlemouths' or 'bristlefishes' due to their shared characteristic of sharp, bristle-like teeth. These fishes typically grow to around 1-3 inches (though some can be larger). They are most commonly found in the mesopelagic zone of the ocean, and are mostly found at depths of over 300 meters (1,000 feet).