Unicorn Fish

Naso is a genus of fish in the surgeonfish family, Acanthuridae. Fish of this genus are known commonly as unicorn fishes because of the "rostral protuberance", a hornlike extension of the forehead present in some species. The unicorn fish are popular with spearfishermen and may be cooked by grilling them whole. Unicornfish primarily live around coral reefs and eat mostly algae as well as roshi (flour) in the Maldives and these are very popular in the Maldives.

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Unicornfish are herbivores that live in tropical waters around coral reefs and are part of the surgeonfish family Acanthuridae. Their name comes from the hornlike extension of the snout present in some species. They range from the Indian to the Pacific Ocean. Two species are common in Hawai’i: the blue spine unicornfish or Kala in Hawaiian (Naso unicornis) and sleek unicornfish or opelu Kala in Hawaiian (Naso hexacanthus). They are characterized by their longhorn projecting from between the eyes extending out to the front of the mouth.

Unicorn fish (Naso Lacepzde), so-called because of the horn or tuberosity projecting from the head of some species, is tropical marine, coral reef fish. They occur in shallow waters of the Indo-West Pacific from the east coast of Africa to the Hawaiian Islands and Ducie in the Tuamotu Archipelago. Naso is one of six genera of surgeonfishes in the family Acanthuridae of the suborder Acanthuroidei. 

Unicorn Fish Genus Naso

The genus Naso includes 20 species of unicorn fish, relatives of the surgical fish and toothfish, in the family Acanthuridae. Although the unicorn fish gets its name from its distinctive protruding nose, not all species in the genus have such horns. Some have only a small bump on the forehead, while others do not emerge. One feature they have in common with the rest of the family is the pair of sharp spines on the caudal peduncle (where the tail meets the body). These "scalpel" weapons are the origin of the name surgical fish. 

The hairy Unicorn or Naso Unicornis (eumecichthys fiski) is a member of the family Acanthuridae also known as Surgeonfish. There are about 80 different types of unicorns belonging to 6 genera in this fish family and all of them have unique characteristics. Unicorn fish have very sharp tongues at the base of their tails on both sides of their bodies, which they use to defend themselves. 

The unicorn fish is endemic from the Indo-Pacific region of Indonesia to Christmas Island in the west and the Andaman Sea, then to the east coast of Africa in the south and is also found in East Hawaiian Islands. 

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These fish get their name from the horn-shaped projection on the top of their heads. Unicorn fish develop horns in early adulthood and lengthen as the fish grow older. It is still not understood why they have such horns. It has not yet been observed whether these horns are used as a defence. 

The unicorn fish also has another amazing ability to change colour almost instantly based on changing mood or changing environment. 

The Naso species is a widely distributed fish, distributed throughout most of the Indo-Pacific region. From the east coast of Africa to the Hawaiian Islands, north of southern Japan and south to the southern edge of the Great Barrier Reef, the Naso species have certainly made their presence known throughout the Indo-Pacific. The fact that there are floating eggs and a prolonged larval stage certainly explains their wide distribution. Most species can be found in water as shallow as 15 feet, and a few others have been seen at depths of more than 500 feet, but the majority of species prefer steep drops and reef walls that occur in the range of 40-120'. 

Dropping downhill gives them easy access to the floating fish environment. They swim underwater, and most species have a silvery-blue colouration, perhaps a camouflage feature that helps them disappear into the vast ocean floor. In addition, they have a unique proportional design, similar to sharks, allowing for greater speed and easier swimming by reducing the turbulence of the water flow around the fish. The tough skin created by their unique scale design is obtained from fish caught for food and used by Native Hawaiians in the past as drum skins. 

Floating fish environments are only used by adults, usually in large schools, as they feed on zooplankton. When young, they usually stay near reef structures and hang out or swim with other unrelated species, except older adults go to school and associate with similar species. The structure of the reef not only protects the fry but also provides food. The fry, for the most part, is strict herbivores, clearing the algae rock at an alarming rate, which allows for the explosive growth of the fish. As the fish grow older, their diet begins to change slowly until the adult fish mainly feed on plankton. In a specific analysis of the intestinal tract (Smith, 1951), the algae were undetectable and, as he put it, the intestinal contents "always were a 'mixture', purely animal tissue. " 

The Unicorn fish are perhaps the toughest of the surgical fish, and in that respect, they make excellent aquarium dwellers. After all, they are very docile and quite resistant to diseases. However, their large size, coupled with their preference for swimming in the water, make them the need for an extra-large aquarium. The size of the reservoir is perhaps the biggest hurdle to overcome when trying to maintain the Naso species for the long term. Small fry easily fit in aquariums that are only 6 feet long, but if the aquarist's intention is long-term care, a six-foot aquarium will not suffice.

Physical Characteristics of the Unicornfish

Let us now have a look at the brief salient features of the unicornfish such as its physiology, diet, habitat and process of reproduction.

1. Physiology of Unicornfish:

The scientific name of the unicorn fish is Naso unicornis. The unicorn fish’s are closely associated with tangs and surgeonfish and they can grow up to a length of 51-61 cm (which makes around 20-24 in). The horn-like tail feature between their eyes pointing outwards begins to grow when a young fish reaches a length of nearly 13 cm (i.e., 5 in) and leads to be considered quite bigger in males. The unicorn fish naso genus is generally not aggressive in nature with each other, but when they get in to fight they tend to use their sharp scalpels by their tails as a strong weapon, but not their horns.

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2. Habitat:

The skin of the unicorn fish naso genus has extremely smooth skin and limited susceptibility to skin diseases in comparison to that of other tangs. They tend to prefer water temperatures between 24 to 26 degrees C (i.e., 75-79 F). 

The unicorn fish are often found in coral reefs, patch reefs, and rocky tropical areas of the Indian and Pacific Oceans and the Red Sea. And a few species of unicornfish are found near Hawaii and Japan.

3. Diet of the Unicorn Fish:

The Unicorn fish are generally active during the day, and unicorn fish swim in groups and feed on algae. Unicorns are herbivores and their food mainly includes benthic algae. They feed on algae deposited on coral reefs. If the algae are not removed from the corals, they will quickly kill the corals, so that the unicorns contribute to the health and cleanliness of the ecosystem. The fish mouth design is perfect, it can remove the algae from the coral without affecting it. The thin and sharp row of small teeth allows the algae to be successfully removed from the coral without damaging them. Since they are not the ones that can be decorated in home aquariums, it seems meaningless to cover dietary adjustments in captivity. 

4. The Behaviour of the Unicorn Fish:

It is said that the entire species has its defence mechanism with the help of the tail root. These are really sharp. In times of danger, this fish will use its tail to stop its attackers from further predation attempts. The blades on their tails can tear anyone's flesh as effectively as a surgeon's medical equipment. Unicorn fish use sharp blades to defend against intruders from foraging areas. Several unicorn fish have only one set of retractable blades, located in slots on both sides of the tail. 

Despite these powerful weapons, the unicorn fish are generally not aggressive, and they spend time swimming across large areas of coral reefs in search of food. 

5. Reproduction:

Like every other fish, the unicorn fish naso genus can also reproduce externally (i.e., they have an external reproduction process). Male and female unicorn fishes swim in the water and release gametes, and fertilization occurs in open water. 

The fertilized eggs are pelagic. In other words, these fish are considered to be pelagic broodstock, releasing their eggs into the water, where they float freely with the current until they hatch. The larval stage of unicorn eggs is very long.

Types of Unicornfish:

There are many kinds or species belonging to the unicorn fish genus Naso and are typically referred to as unicornfish because of their particular and interesting feature of a long pointed protuberance in the middle of their heads. The Unicorn fish genus naso is found to belong to the same family as surgeonfish, i.e., Acanthuridae, and there are nearly 20 different species that have been recognized to date. It is often observed that the unicorn fish have the capacity and are capable of becoming extremely aggressive and dangerous with their own method but they are usually the kind of peaceful and non-combative with other non-aggressive marine water or seawater creatures of similar size. 

As it is already mentioned that there are nearly 20 species recognised under the family of unicorn fish genus Naso are available and often used as pets, the unicorn fish are often found as aquarium friendly marine creatures. So, a few of the most fascinating and interesting species of unicornfish are listed below.

1. The Bluespine Unicornfish

• Physiology of the Blue Spine Unicorn Fish

The body is usually grey-green, with a bone horn or horn protruding from the front of the head in front of the eyes. The dorsal and anal fins are pale yellow with thin blue lines. There are two blue plates on both sides of the tail handle with sharp, forward-pointing thorns. Thick leathery skin with tiny, non-overlapping scales and small teeth with finely serrated edges. The caudal fin lobes extend as thin threads; it is more pronounced in males. The blue-spine unicorn fish can reach approximately 27.6 inches (70 cm) in length. 

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• Diet

The diet includes dense green leafy brown algae. 

• Habitat

Occurs the is distributed in the Indo-Pacific, from the Red Sea and East Africa to the Marquesas Islands, through the tropical Pacific Ocean to southern Japan, through Micronesia and east of Hawaii. 

Juvenile fish live on clear coastal coral reefs with algae growth.  Adults prefer shallow reef slopes near deep water.  is found in rivers, trenches, lagoons, and coral reefs by the sea, especially in areas with heavy swells, and its depth generally does not exceed 33 feet (10 m). 

• Reproduction:

The unicorn fish often has been observed to practice pairing eggs, especially in the outermost area of ​​the feeding group. In some areas, it has been observed to migrate in groups around the outer reef edge and spawn during the full moon and new moon. 

2. White Margin Unicornfish

• Physiology of Whitemargin Unicornfish:

The white-margin unicornfish (Naso annulatus) is a sportfish that lives on coral reefs. White-margin unicornfish are found throughout the Indo-Pacific Ocean and are common in the rocky tropical areas of coral reefs, the Indian Ocean, the Pacific Ocean, and the Red Sea. Some are said to have been found near Hawaii and Japan. This species lives on coral reefs in the depth range of 1 - 60 m, which is 197 feet high. 

The length of Whitemargin can reach 100 cm (3.3 ft), making it one of the largest members of the surgical fish family, making divers happy, especially underwater photographers who discover adult specimens while diving. 

The colour of the white margin unicornfish range from olive to brown colour; and also sometimes it can vary up to light blue, black tail with broad bands, interband membranes, narrow edges, white filaments. The dorsal and anal margins of juvenile fish are thin white, with a white mount on the tail peduncle, the tail is black, and the edge is white. 

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• Diet:

These fish are mainly active during the day, swimming in groups of algae. As pure herbivores, their favourite food includes green-leaf brown algae like Sargassum. 

• The Behaviour of the Whitemargin Unicorn Fish:

When the juvenile fish grows to about 5 inches (13 cm), the angular appendix between the eyes begins to grow, while the male tends to be slightly larger. The fish never uses this horn as a weapon, or even to protect itself, but uses its sharp scalpel-like thorn near the tail as a weapon.

• Habitat:

They are usually inhabited in the benthic juvenile fish and sub-adults live on coral reefs and rocky coasts, and adult fish live in open water near the front of exposed coral reefs. 

3. Bignose Unicornfish:

• Physiology of the Blue Spine Unicorn Fish:

Big Nose Unicorn is an important member of the Acanthuridae family. Although it is a unicorn fish, it does not have the characteristics seen in many other species. "angle". The adult is dark magenta grey, with small blue vertical stripes on both sides, small blue spots near the abdomen, and a typical thick blue stripe from the eyes to the muzzle. The unicorn big-nosed fish has a prominent nose and body covered with bright blue spots. It inhabits deep lagoons and coral reefs, where it forms small groups and feeds on zooplankton. 

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The juvenile large-nosed unicorn is dark yellow-green with small blue spots and blue lips. As they mature, they will develop shades of magenta and purple. 

• Diet:

Just like most of the unicorn fish species, even the big nose unicorn fish live alone and feed on algae that grow on the reef. 

• Habitat:

They are often inhabited in the rocks and coral reefs and in the benthic juvenile fish in protected habitats and debris slopes; adult fish in the middle waters near the front of the exposed reef. 

The large-nosed unicorn is widely distributed in the Pacific and Indian Oceans, from the coast of KwaZulu Natal to Japan, the Great Barrier Reef and the Galapagos Islands. Their preferred habitat is the deep lagoons of coral reefs and the edge of the ocean, where they sometimes gather in groups to feed on small zooplankton, especially copepods. 

• Reproduction: 

The reproduction has been observed to practice pairing eggs, especially in the outermost area of ​​the feeding group. In some areas, it has been observed to migrate between groups around the outer edge of the reef and spawn during full and new moons.

These are few species of the unicorn fish genus naso and these are often found in aquariums as they prefer to be grown in any environment, these aquarium fish will add beauty and boost the environment with their active daytime routine.

Conclusion

The unicorn fish Naso genus species is characterized by the following: 

• Body depth ranges from approximately 2.0 inches (infants) to 2.42.6 inches (adults); adults have a sharp bony horn on the forehead that protrudes forward at eye level but does not extend to the front of the mouth (The horn is first a bulge on the forehead, about 12 cm long). 

• The unicorn fish is straight from nose to corner, with an angle of approximately 45 °; 2 stalked plates with well developed front scimitar spines; caudal fin slightly absent when young and truncated with filamentous lobes in adulthood. 

• Males of this species have significantly longer horns, larger pedicel keels, and longer tail filaments than females of the same size; the back of the body is light yellow to olive-grey, and the ventral surface is lighter, with blue peduncles and dragons Bony spurs; white or blue lips. 

• Blue area sometimes appears around pectoral fin; the dorsal and anal fins are light yellow with blue edges; tail fin base is orange, shading is grey, trailing edge is broad, light green, and tail fin filament edges are blue, a short-lived colour Stage is a light green spotted area below the spiny part of the dorsal fin, which narrows and ends under the pectoral fin.