User:Annavc3/Viperfish

Bioluminescence
Chauliodus species utilize their ability to bioluminesce for two distinct purposes: attracting prey and avoiding predators. They show distinct anatomical adaptations for the two functions. Chauliodus possesses a bioluminescent lure located at the tip of its first dorsal ray, which it uses to attract prey by swinging it forward in front of its mouth.

Chauliodus has photophores along the ventral side of its body that emit light through adrenergic nervous control. The distribution of this light closely matches the distribution of light in mesopelagic and bathypelagic ocean zones, making it difficult for predators to see the fish. This type of camouflage is called counter-illumination.

The presence of photomicrobes in the visceral organs of Chauliodus sloani indicates that bioluminscent microbes are likely responsible for the Chauliodus's ability to luminesce.

Body Plan
Chauliodus species are recognized by their large, fang-like teeth. They are so long that they would pierce the brain of the fish if misaligned.

The eyes of Chauliodus sloani maintain a constant size and proportion throughout growth of the fish. In the retina, several rows of rod cell "banks" grow upon each other, increasing in number with size of the fish. This opposed the typical vertebrate retina, which only has one layer of receptors.

The first dorsal ray of Chauliodus is elongated, hinged, and connected via musculature; allowing it to swing forward. The tip of this ray has light organs. This fish lack scales, and instead is covered with hexagonal pigment patterns covered in an opalescent, slimy substance.

One species of viperfish, C. sloani, have a sampled standard length of 64.0 to 260.0 mm, with a mean SL of 120.3mm. The same species has a mean weight of 5.66 grams. Representatives from Chauliodus pammelas and Chauliodus sloani display a size-based depth differential. Individuals of a lesser mass are found at shallower depths and individuals of larger mass are found at deeper depths, below 500 meters. However, at nighttime larger viperfish can be found in shallower depths. Depth is restricted by temperature, and the upper thermal limit of viperfish is 12° to 15° C.

Habitat
Viperfishes live in meso- and bathypelagic environments and have been found dominating submarine calderas such as the Kurose Hole, which is the site with the highest Chauliodus density known in the world. Viperfishes also engage in diel vertical migration, meaning they migrate up into more productive waters during the night to feed. Temperature is another restricting factor in viperfish's vertical distribution in the ocean. In tropical waters, viperfish tend to stay in the deep layers and not migrate much, while in temperate waters viperfish are more actively migrating and even interacting with epipelagic predators.

Migratory Patterns
Vertical movements of viperfish are influenced by temperature. It was observed that the upper limit of distribution is restricted by temperature (12-15 °C). That is observed to affect vertical habitat and trophodynamics. In most tropical waters, it is likely that the viperfish exists full time below 400 meters. In temperate regions, viperfish trophically interact with epipelagic predators at superficial waters.

Many sub-species in the Stomiidae family participated in diel vertical migration. In migrating to the surface (400m depth) at night, they prove their ability to withstand large temperature changes of up to 7°C daily. They have been recorded in waters ranging from 4 to 14.5°C, highlighting the wide range of temperatures viperfish are capable of surviving in.

Viperfish have previously been recorded in the Italian waters off the western Mediterranean Basin, the Adriatic Sea, the Greek waters of the Aegean Sea, and in the Turkish waters of the Levant Sea. Viperfish have rarely been seen off the Algerian coast by Dieuzeide. They have been reported to occur off the northern Tunisian coast.

Reproduction
Despite the abundance of viperfish in the meso- and bathypelagic, their reproductive ecology is widely unknown. This is due to research surveys rarely being able to catch mature adults, as well as the general lack of research on fish reproductive ecology in the deep sea. It is likely, however, that viperfish share a similar reproductive ecology to other dragonfishes which have been studied more extensively (under Stomiidae family).

Viperfish are gonochoristic, meaning that they don't exhibit both testicular and ovarian tissue simultaneously in their gonads. They reproduce through spawning, with a study on dragonfishes indicating that males are able to spawn sperm continuously whereas females display asynchronous oocyte development and batch spawning. That same study showed a skewed 1:2 sex ratio favoring females in their collection of over seventy Chauliodus sloani viperfishes in the Gulf of Mexico.

Two Chauliodus macouni eggs were recovered in the Columbia River in Oregon (likely displaced by strong Pacific currents), indicating a potentially long incubation period for viperfish eggs.

Feeding
Viperfishes, depending on the species, prey on other pelagic fishes and crustaceans. Stomach contents of captured individuals have contained lanternfishes, bristlemouths, copepods and krill. Based on the diel vertical migration of its prey, viperfish are assumed to be epipelagic migrants that search surface waters for food. The prey for viperfish, specifically the species C. sloani, are highly specific and of high abundance with low levels of occurence.

Viperfish are able to maximize energy input by consuming few but large prey. In order to support the specificity of feeding, the viperfish has multiple adaptations such as a large-toothed mouth, modifications in its skull to allow for a wide opening of its mouth, and elastic stomach and body skin to compensate for large prey.

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