The black dragonfish compared to the creature from Alien. Image via
WWF
The ocean is, in many ways, another world. It is a place that is quite different from the Earth that we know and experience on a day-to-day basis. Case in point: Meet the black dragonfish. This little creature is also known as
Idiacanthus atlanticus, and to be frank, they look rather terrifying. In fat, they look remarkably like the creatures from the Alien moves. However, you really don't have much to fear from these little guys, as they are, well, little. Also, they live deep in the ocean, far deeper than your average human will ever venture.
The females are some 15 inches long (40 cm). That may sound like a fairly good size, but as you can see, lot of their length comes from their long, tail-like structure. Their mouths, by comparison, are rather little, and they use them to eat other fish The males barely reach 2 inches (5 cm) in length and have a number of other notable differences. They don't have any teeth or the long structure extending from their chin, and they are brown and have no digestive system...essentially, they look nothing like the female dragon fish.
The distinct differences between the two sexes is known as "sexual dimorphism," and it is believed that the males' only purpose is reproduction (after all, there isn't a whole lot that you can do with no digestive system).
Black dragonfish. Image via MABRI
Black dragonfish can produce their own light, which is actually rather common in creatures that live in the black recesses of the ocean. You can find these tiny terrors more than a mile beneath the waters (2,000 meters). However, unlike most bioluminescent predators, which use their light primarily to attract prey, the black dragonfish can also see its own light. Ultimately, because it can perceive a red as well as blue-green light, the creature can hunt down its prey with its ocular advantage. Interestingly, the light produced by the fish is often such a long wavelength that it is nearly in the infrared part of the spectrum. Consequently, the light is barely visible to the unaided human eye.
The light of the black dragonfish can be such long wavelengths that it is almost infrared and barely visible to the human eye. The ability to produce this type of light gives the black dragonfish an enormous advantage over its prey as it can find its way to unsuspecting prey through the deep dark depths of the ocean.
If these creatures weren't already interesting enough, in the larva stage,
the eyes of the larvae appear as long stalks that dangle out of the body. Eventually, they retreat as the fish ages and reaches maturity.
A preserved specimen of a larval deep-sea black dragon fish (Idiacanthus). Image credit: Carole Baldwin)
WATCH: The Black Dragonfish
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