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Viperfish

life science Maturity 5-7 Next article →

Viperfish are specialized predatory fish belonging to the genus Chauliodus. They inhabit the mesopelagic and bathypelagic zones of the ocean. These zones are often called the twilight or midnight zones. This is because very little sunlight reaches these deep depths.

Chauliodus (Samoa)
Chauliodus (Samoa)

Viperfish play a vital role in deep-sea ecosystems. They are found in tropical and temperate oceans across the entire globe. Some populations thrive in the Mediterranean Sea or the Adriatic Sea. Others live in the Pacific Ocean or near the Aegean Sea.

To survive in the dark, viperfish use a process called bioluminescence. This is the ability to produce light through chemical reactions. In species like Chauliodus sloani, light-producing bacteria live inside their organs. These light organs are called photophores. Viperfish use photophores for two very different survival strategies. First, they use a lure on a long dorsal ray. This ray is hinged and connected to muscles. The fish swings this glowing tip forward to attract prey.

Head of a pacific Viperfish 4037
Head of a pacific Viperfish 4037

Second, they use photophores on their ventral, or belly, side. This light helps them perform counter-illumination. This means they match the dim sunlight coming from above. By doing this, they become harder for predators to see from below.

The anatomy of a viperfish is built for extreme hunting. They possess prominent, needle-like teeth that are extremely long. These fangs are so large they could pierce the fish's own brain if misaligned. To eat, they use a specialized "loosejaw" arrangement. This allows their jaws to extend and open very wide. They also have a unique ventral jaw muscle called the Aω muscle. This muscle increases their biting force and jaw-closing speed.

To handle large meals, they have elastic stomachs. Their skin is also elastic to accommodate big prey. This allows them to maximize energy by eating large, infrequent meals.

There are currently nine recognized living species of viperfish. These include Chauliodus barbatus and Chauliodus danae. Other species are Chauliodus dentatus and Chauliodus macouni. We also recognize Chauliodus minimus, Chauliodus pammelas, and Chauliodus schmidti. The last two are Chauliodus sloani and Chauliodus vasnetzovi. Scientists have also discovered fossil species from the Late Miocene epoch. These include Chauliodus eximus from California. They also found Chauliodus testa on Sakhalin Island.

Head of a pacific Viperfish 4037
Head of a pacific Viperfish 4037

Growth and physical traits vary between these species. For example, Chauliodus sloani has a mean length of about 15 centimeters. They have a mean weight of roughly 150 grams. Their bodies are covered in five rows of silvery scales. However, these scales are easily shed or dissolved during preservation. Beneath the scales, the skin has hexagonal pigment patterns.

Interestingly, their eyes do not change size as they grow. Their retinas contain multiple rows of rod cell banks. This is different from most vertebrates that have only one layer. This extra layer likely helps them see in low light.

Viperfish are known for a behavior called diel vertical migration. This means they move up and down in the water column daily. At night, they swim toward the surface to find food. They can survive massive temperature changes during this trip. They can handle a range of up to 12 degrees Celsius. This movement is heavily influenced by water temperature. In many tropical areas, they stay below 200 meters. In temperate regions, they interact with predators in shallower waters.

While they are abundant, much about their reproduction remains a mystery. Most research surveys fail to catch mature adults in the deep sea. We do know that they are gonochoristic. This means individuals are either male or female. They reproduce through a process called spawning. In some studies, a sex ratio of 1:2 was found. This means there were twice as many females as males. Some evidence suggests their eggs may have a very long incubation period.

Chauliodus (Samoa)
Chauliodus (Samoa)
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🖼️ Images & Media (3)
File:Grand croc petit fil (Chauliodus sloani) de Méditerranée (Ifremer 00676-78846 - 31633).jpg
Grand croc petit fil (Chauliodus sloani)...
File:Head of a pacific Viperfish 4037.jpg
Head of a pacific Viperfish 4037.jpg
File:Chauliodus (Samoa).jpg
Chauliodus (Samoa).jpg
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