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Today on Animal Fact Files we’re discussing stoplight loosejaws. For more facts on other interesting animals, please subscribe! These interesting fish were requested by Jtkt0mb. We hope you learn something new today!

Stoplight loosejaws are a type of deep-sea dragonfish (Stomiiformes) who belong to the Malacosteus genus. After much taxonomic revision since their discovery in 1848, there are two species of stoplight loosejaws: northern stoplight loosejaws (Malacosteus niger) and southern stoplight loosejaws (Malacosteus australis) - boy, with names like that someone was really using up some brain cells during that day in the office. The name Malacosteus means ‘soft boned’. This is in reference to the stoplight loosejaw’s soft skeleton which is so soft that the scientist who first observed them (William Orville Ayres) stated that even the hardest points of the stoplight loosejaw’s skeleton could be pierced with a needle with greatest of ease. Sounds like somebody is not going to win during the skeleton war…

Stoplight loosejaws eat by dislocating their heads and jettisoning their lower jaw forward. I suppose having a soft skeleton makes this less painful? While they’re able to eat fish, and likely can consume large fish as some research indicates they can distend their stomach to hold more food, their favorite food are crustaceans called copepods. These small crustaceans are important to stoplight loosejaws not just a source of food but also because they help stoplight loosejaws see far-red light. Copepods eat bacteria that provide the chemicals needed to see far-red light; so, when the stoplight loosejaw eats the copepod, it also gains these chemicals. Sunlight can not penetrate into the deep ocean so most organisms rely on the light they and other organisms produce. This light production is called bioluminescence. We’ve talked about bioluminescence on other episodes of AFF, but basically bioluminescence is the emission of light by a living organism. Most creatures that are bioluminescent produce blue light, but stoplight loosejaws can produce red light. Maybe that’s part of where their common name comes from? The ability to produce red light is rare among bioluminescent creatures, and stoplight loosejaws, thanks to the chemicals obtained by eating copepods, have the almost completely unique ability to see red light in the depths of the ocean. What this means is that stoplight loosejaws are able to see each other’s red light when other fish can not. This feature can give stoplight loosejaws a leg up… er… fin up? In their watery habitat.

Stoplight loosejaws live in the ocean between about 60 degrees north latitude and 30 degrees south latitude. They live at depths between ⅓ of a mile (500m) to nearly 2.5 miles (4,000m). To put that into perspective, stoplight loosejaws can live as far down in the ocean as almost halfway up the tallest mountain on earth. That’s pretty dang deep. For the most part they appear black in color though some have been documented with small white spots. They can reach about 10 inches (25.6cm) in length and, although they’re fish, they’re covered in skin and do not possess scales. They have relatively large eyes compared to other deep-sea fish, and due to just general difficulty in ability to observe them, we don’t really know much about their reproduction or how long they can live. It has been noted, however, that male stoplight loosejaws have larger bioluminescent areas than females. So, it’s possible that males use their lights in courtship displays, but, like we said, this is just speculation. Still, I like the idea of this crazy looking fish dancing around at the bottom of the ocean for all the lady fish.

As it stands, there is not enough evidence to determine is stoplight loosejaw populations are under any kind of threat, but research seems to indicate that there are quite a lot of individuals down there with one museum quoting the ownership of more than 100 specimen. Only time, and some advancements in deep-sea exploration, will tell for these fantastic fishes.

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