Pacific viperfish

The Pacific viperfish tend to be the largest of the species,[3] 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.

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.

[5] The fangs of the pacific viper are abnormally long that its jaw is extended out, so its teeth can fit outside of its mouth.

[8] Furthermore, its hinged skull allows it to rotate upwards when looking to attack and, ultimately, swallow a large prey.

[9] 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.

[7] The photophore also serves as a communication tool; it is used by the viperfish to signal a mate or ward off potential rivals in the area.

The Pacific viper lies motionless in the darkness and waves its blinking lure over its head waiting on its meal to arrive.

Specifically, one of their light organs is found on a long dorsal fin which acts as a lure for when searching for prey.

Due to darkness and limited mates it is best suited that the Pacific viper externally spawn (biology) or oviparous.

In 2018, Susumu Ohtsuka, Dhugal J. Lindsay and Kunihiko Izawa described a new genus and species of pennellid copepod, Protosarcotretes nishikawai, from a single ovigerous female infecting a Pacific viperfish collected from the deep-waters of Suruga Bay, Japan.

[17] The discovered a parasite attached to the posterior to the right eye of the host fish, and this discovery marked the only documented case of this species.

Head of the pacific viperfish
Parasite on the Pacific viperfish