Paracanthurus Hepatus – Weird Behaviors, Habitat and 4 Facts To Know

Paracanthurus Hepatus

Last updated on August 10th, 2022 at 07:58 pm

Paracanthurus hepatus is a type of Indo-Pacific surgeonfish. A popular fish in a marine fish tank, it is the only member of the genus Paracanthurus. A number of typical names are associated to this species, such as regal tang, palette surgeonfish, blue tang (causing confusion with the Atlantic species Acanthurus coeruleus), royal blue tang, hippo tang, blue hippo tang, flagtail surgeonfish, Pacific regal blue tang, and blue surgeonfish.

Description of Paracanthurus hepatus

Paracanthurus Hepatus

Paracanthurus hepatus has a royal blue body, yellowtail, and black “palette” style. The lower body is yellow in the west-central Indian Ocean. It grows to 30 cm (12 in).

Grownups generally weigh around 600 g (21 oz) and males are normally larger than females. This fish is rather flat, like a pancake, with a circular body shape, a pointed snout-like nose, and small scales. The blue tang has 9 dorsal spinal columns, 26 – 28 dorsal soft rays, 3 anal spinal columns, and 24 – 26 anal soft yellow rays.

They are defined by the dynamic sky blue pigmentation of their oval-shaped bodies. Structures called iridophores on the exterior of the fish add to this coloration. Adults have dark narrow lines of dark blue on the dorsal half of their body.

This color extends from the eye on the anterior end and continues to the posterior end. This pigmentation is darker near the posterior end and is black near the tail. A circular patch of sky blue pigmentation lies straight behind the pectoral fin. The caudal and pectoral fins are intense yellow. The yellow extends in a “V” shape from the caudal fin to a point just beyond the caudal spinal column.

Pigmentation of paracanthurus hepatus changes as they develop; juveniles are intense yellow with blue areas near their eyes, and their dorsal and anal fins are tipped in light blue. Their body becomes blue as they grow.

Paracanthurus hepatus behavior

Although paracanthurus hepatus are periodically seen alone, most are seen in pairs or little groups. In the reef, they school for security. A group of fish, each possessing a poisonous and sharp caudal spinal column is possibly problematic to predators; very few predators swim into the middle of a school of surgeonfish to feed off the members of the group. Typical surgeon aggregate with other genera of surgeonfish, including Acanthurus, Ctenochaetus, Naso, Zebrasoma, and Prionurus.

Male typical surgeonfish might have violent encounters with one another, circling each other and showing their caudal spine. The hue of their blue coloration changes as the encounter becomes more intense. Males attempt to injure one another with their poisonous spines, each one swimming closer to the other up until its caudal fin can be manipulated to cut the other.

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This caudal spinal column may have an effect on the social standing of paracanthurus hepatus with the other marine fish in the area. A fish of this species accomplishes its dominant status over formerly dominant fish by flashing their poisonous caudal spinal column. The most dominant individual frequently has the biggest breeding area.

When frightened, some typical surgeon, especially juveniles, hide behind live rocks or within branching corals. An alarmed fish secures its position within the head of the coral by extending its caudal spinal column into the coral.

This prevents a predator from pulling the fish out of its hiding place if discovered. If identified by a predator, a typical surgeon “play dead”, resting on their side, without any movement. They are frequently mistaken for dead and passed over by predators. In the fish tank trade, new enthusiasts worry that typical surgeon has passed away when they play dead. Within a couple of days of introduction to an aquarium, paracanthurus hepatus  become more comfortable with their environment and likewise often get dominant status.

Communication and Perception of Paracanthurus hepatus

Paracanthurus Hepatus

Paracanthurus hepatus can interact by altering their pigmentation. These color changes depend on the conditions and how they perceive their environment. Under stress, for instance, their blue pigmentation deepens. The black marks along the body might become bleached a little and the markings less noticeable.

The iridophores causing the brilliant blue coloration appear smaller and less iridescent, thus the darker shade of blue. Other fish in the neighborhood can spot this color change and infer prospective issues. Color modification also takes place throughout stimulation such as male supremacy interactions or breeding.

The coloration around the caudal spine acts as a warning to other species. In a typical surgeon, the yellow triangular coloration extends simply beyond the caudal spinal column.

In other species of surgeonfish, the place of the caudal spine may even be highlighted by a color that is not otherwise present on the body of the fish.


Location of Paracanthurus hepatus

The regal blue tang can be found throughout the Indo-Pacific. It is seen in the reefs of the Philippines, Indonesia, Japan, the Great Barrier Reef of Australia, New Caledonia, Samoa, East Africa, and Sri Lanka. The regal blue tang is one of the most typical and most popular marine aquarium fish all over the world.

Wyoming White Clownfish "Amphiprion Ocellaris"

They live in sets, or in small groups of 8 to 14 individuals. They can also be discovered near cauliflower corals on the seaweed side of coral reefs.
The regal blue tang is ranked LC (least concern) by the World conservation Union (IUCN), but the vulnerability is low.

Geographical Range

Paracanthurus hepatus , Paracanthurus hepatus, are strictly marine fish that generally inhabit tropical coral reefs in waters with a strong current. They might move seasonally, happening at greater latitudes when water temperatures allow.

Generally, paracanthurus hepatus  range between 30° north and south latitude and 32° east to 170° west longitude in the Indian and Pacific Oceans. Individuals discovered in other areas are presumed to have been released from aquaria.

Paracanthurus hepatus Diet plan

As a juvenile, its diet consists mostly of plankton. Adults are omnivorous and eat plankton, but will likewise graze on algae. Spawning occurs throughout late afternoon and night hours. This event is indicated by a change in color from an uniform dark blue to a pale blue. The fish is crucial for coral health as it consumes algae that might otherwise choke it by overgrowth.


Typical surgeon are strictly marine and can be found in tropical and sub-tropical seaside areas where temperatures are between 24 and 26° C. They gather together near Pocillopora eydouxi, a kind of coral with branching extensions, which serve as a protective hiding place when threatened.

Reefs offer plant product, such as algae, necessary as food for typical surgeon. Typical surgeon remain at epipelagic depths in between 2 and 40 m.

Life process

Males strongly court female members of the school, resulting in a fast upward spawning rush towards the surface area of the water throughout which eggs and sperm are launched. The eggs are little, roughly 0.8 millimeters (1⁄32 in) in diameter. The eggs are pelagic, each consisting of a single bead of oil for flotation. The fertilized eggs hatch in twenty-four hours, revealing small, clear larvae with silvery abdomens and primary caudal spinal columns. These fish reach sexual maturity at 9 – 12 months of age.

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Development of Paracanthurus hepatus

Larvae of paracanthurus hepatus  hatch about 26 hours after the small eggs are laid. Larvae are significantly underdeveloped and do not have a heartbeat at hatching.

Larvae are nurtured by yolk from the egg. Recently hatched larvae are resilient however, stay in a resting state till the heart begins to beat, as much as 5 hours after hatching.

2 days after hatching, fins and pigment in the eyes begin to develop, and larvae begin to make brief swimming movements. Advancement continues with jaws and the gut, and by the seventh-day scales and intestines start to form.

Speed of advancement belongs to light intensity. Larvae mature after about 37 days.

Juvenile paracanthurus hepatus look like adults, however, they differ in pigmentation. Juveniles likewise have a more rounded caudal fin than grownups. Additionally, the forward and poster tips the caudal fin in grownups extend beyond the middle section of the fin.


Paracanthurus Hepatus

Paracanthurus hepatus gather in breeding groups, made up of both females and males. These groups spontaneously form. Groups dissolve and reform a number of times prior to spawning. A group begins to swim upward and, at the crest of this upward movement, they launch their gametes.

Paracanthurus hepatus are relayed spawners; eggs and sperm are released directly into the water, and fertilization occurs externally. The quickened speed of their swimming throughout breeding is thought to permit for dispersal and blending of the sperm and eggs. Eggs are then brought away by currents.

On event, paracanthurus hepatus have actually been noticed breeding with individual mates instead of in groups. In this case, a male’s coloration can change. The male and female then circle around each other, revealing their pigmentation prior to breeding.

Mating Systemmonogamous polygynandrous (promiscuous)

Paracanthurus hepatus breed throughout cooler months, though the time of year differs with the area and water temperature. In the Pacific, reproduction activity is most intense from December to June.

In areas where water temperature does not change significantly with the season, reproduction can occur throughout the year. Breeding is presumed to peak throughout the summer in these areas, however paracanthurus hepatus in these locations have spawning episodes throughout the year.

Throughout months of prime temperature level, females release their eggs about once a month. With each spawning, females can launch up to 40,000 eggs into the water column.

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High amounts of eggs and sperm make the water cloudy in appearance.

Eggs of paracanthurus hepatus hatch between 25 to 28 hours (typical 26 hours). Larvae develop quickly and feed in varieties off the coast. Sexual maturity is measured by size and not measured by age.

Males normally reach sexual maturity around 11 cm in length. Females, however, do not reach sexual maturity till about 13 cm in length.
There is no parental investment amongst paracanthurus hepatus.

As broadcast spawners, males, and females distribute after launching their gametes into the water column.


The paracanthurus hepatus can live more than thirty years in the wild. In aquariums, where they more easily acquire diseases, paracanthurus hepatus generally do not live more than twenty years and more frequently survive just 8 to 12 years.

Value to human

The regal blue tang is of small commercial fisheries value; nevertheless, it is a baitfish. The flesh has a strong smell and is not extremely prized.

Although, this fish might trigger ciguatera poisoning if consumed by people, nevertheless, regal blue tangs are gathered commercially for the aquarium trade. Managing the tang risks the opportunities of being badly cut by the caudal spine.

These spinal columns, on both sides of the caudal peduncle, are extended from the body when the fish is stressed. The quick, thrashing sideways motion of the tail can produce deep injuries that result in swelling and staining, posturing a threat of infection.

It is thought that some species of Acanthurus have venom glands while others do not. The spines are used only as a technique of defense against aggressors. Two sharp spinal columns protrude at the caudal peduncle – the location where the tail joins the remainder of the body.

Conservation of paracanthurus hepatus

The species is categorized as the least concern by the IUCN, however, it is threatened by overexploitation (mainly for the aquarium trade) and damaging fishing practices. Given that it is dependent on fragile coral reef habitats, habitat damage likewise constitutes pressure in parts of its range.