The deep sea has been less explored by humans than the surface of the moon! Down there in the depths, under bone crushing pressures, live some of the most alien things you could possibly imagine. Here are a few of the many fascinating residents of this barely touched world:
Deep Sea Hatchetfish
This silvery little fish belonging to the family of Sternoptychidae, whose face looks like it’s seemingly frozen in a silent scream, resides in most of the world’s oceans at depths of up to 4,950 feet. Their huge, tube shaped eyes allow them to catch the very little light that manages to reach even the deepest waters of their range. That way, they can see prey and watch out for predators. They also have a special defense mechanism that allows them to hide when nearer the surface. Special bioluminescent photophores, or light producing organs, will mimic the light of the surface waters to create the illusion of the fish’s disappearance. This is called counter-illumination. As one of the main food sources for other creatures in the deep, it’s a handy trick to avoid being eaten.
The stoplight loosejaws are a small group of dragonfishes in the genus Malacosteus found below the depth of 1,640 feet. They too have light producing photophores, which is where they get their name. The largest one emits red light while the smaller one emits green. Red wavelengths from sunlight don’t reach that far down, so the color red is essentially invisible to most creatures, which is a reason why many of them have red bodies. The stoplight loosejaws, however, are a few of the only ones that can actually emit their own red light and detect those wavelengths. This enables them to use those photophores as floodlights to spot prey. The “loosejaw” part of their name refers to the minimal attachment of the lower jaw to the upper portion of the skull. They have no floor to the lower jaw at all and it is only connected by small hinges. This reduces water resistance so they can snap their jaws shut more quickly when they find something edible.
Deep Sea Anglerfish
Deep sea anglerfish is a term for many fish in the family Ceratiidae. This is possibly one of the better known deep water fish because of its fearsome appearance. They all share the trait of using a lure to attract prey to them since they aren’t the fastest swimmers in the ocean. This tactic also conserves the precious energy that is hard to come by, as there is little food down where they live. All they have to do is wait and then pounce. Some have light producing bacteria in their lures that makes them even more attractive to potential meals. That’s cool and all, but the weirdest thing about these species is their sexual dimorphism (morphological differences between sexes). The fish we are all familiar with are only the females. The male is actually only a few millimeters long and permanently fuses to the female’s body as a parasite when the two meet. His only purpose is to provide genetic material to the female. As breeding opportunities are so rare down there, this is a clever, albeit creepy, evolutionary adaptation. Once the female finds a mate, she’ll never be lonely again.
1. Cronin, Thomas W. “Camouflage via Emitted Light – Counterillumination.” Visual Ecology. N.p.: Princeton UP, 2014. 315-19. Print.
2. Kenaley, Christopher P. “Revision of the stoplight loosejaw genus Malacosteus (Teleostei: Stomiidae: Malacosteinae), with description of a new species from the temperate southern hemisphere and Indian Ocean.” Copeia 2007.4 (2007): 886-900.
3. Pietsch, Theodore W. “Dimorphism, parasitism, and sex revisited: modes of reproduction among deep-sea ceratioid anglerfishes (Teleostei: Lophiiformes).” Ichthyological Research 52.3 (2005): 207-236.