The Pacific viperfish, Chauliodus macouni, is a predatory deep-sea fish found in the North Pacific. It is reported as being either mesopelagic or bathypelagic, with diel vertical migration to shallower waters. The Pacific viperfish is one of the nine different species that belong to the genus Chauliodus, the viperfish. The Pacific viperfish tend to be the largest of the species, typically reaching lengths of up to 1 foot and are considered an example of deep-sea gigantism. The length-weight relationship of the pacific viperfish varies with sex with females tending to be longer and heavier than males.
Description
The pacific viperfish is classified as one of the most ferocious deep seas fish for its size. They are iridescent dark silver-blue color in life with pale fins. They can also be a light black color with blue fins. The coloration of the Pacific viperfish has what is known as ultra-black skin to reduce the reflection of other bioluminescence surrounding them to better camouflage in the deep sea. This ultra black skin reduces the amount of light reflected from the body of the viperfish which scatters the light using the melanosomes in its skin that are optimized for reduced reflectance. Looking at the mouth and curvature of teeth one can easily recognize the pacific viperfish. The fangs of the pacific viper are abnormally long that its jaw is extended out, so its teeth can fit outside of its mouth. The fangs rest near the viper's eyes. These fangs are the viper's way of killing fish, the viper will swim at high speeds at its prey and impale them in the process. The jaw of the Pacific Viperfish is also hinged in order to fit large sized prey for its size. It also has a loosejaw that improves the closing of the jaw by facilitating faster closing to better capture prey that may be harder to catch. Furthermore, its hinged skull allows it to rotate upwards when looking to attack and, ultimately, swallow a large prey. High speed collisions and force in bites have cause the viperfish to adapt to high impact. The vertebrae that is located right behind its head is used a shock absorber, very similar to an air bag. They are excellent maneuvers in areas that receive significantly less sunlight than uppermost regions. This is accredited to a protein in the rods known as rhodopsin, composed of the transmembrane protein opsin, and retinal. The viperfish lacks a swimbladder and has large amounts of acidic glycosaminoglycans in its gelatinous tissue that are hypothesized to be used as a possible buoyancy mechanism.
Hunting and feeding
Pacific Viperfish are also one of the many deep-sea fishes that migrate vertically to feed on fish at night. This feeding mechanism is referred to as diel vertical migration (DVM).
Viperfish are often caught with empty stomachs. The viperfish's diet consists of fish with myctophids and slender fangjaws being their most common prey.
According to O'Day (1973) luminescent silhouetting may aid the fish in mating, spacing themselves out as they hunt, maintaining conspecific aggregations, warning potential predators of their own formidable size, or perhaps allowing them to escape from predators by temporarily blinding them. These functions, however, remain speculative.
The Pacific viperfish has large photophores that are found on the ventral side, as well as the ventrolateral sides, where they create rows. These photophores present themselves in luminous tissue that is evident on the dorsal and ventral portions of the fish, as well as the fins. This luminescence was described as having a “blue color” by a scientist who had the fish in a tank for 45 minutes before it expired. It was further noted that luminescence could be induced by prodding the fish with a glass rod, which would cause the luminescence to pulse through the body of the fish before returning to its static glow in the ventral region. It was further noted that placing the fish in a weak adrenaline-seawater solution caused luminescence to increase (as would applying a topical adrenaline solution or injecting adrenaline intravenously. There is a simple, un-pigmented type of luminescent organ found in these fish that is found within a gelatinous sheath which surrounds the entire body.