The pyramid butterflyfish (''Hemitaurichthys polylepis'') is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of marine

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

, a

butterflyfish The butterflyfish are a group of conspicuous tropical ocean, marine fish of the family Chaetodontidae; the bannerfish and coralfish are also included in this group. The approximately 129 species in 12 genera are found mostly on the reefs of the ...

belonging to the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Chaetodontidae, native from central

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

Description

The pyramid butterflyfish is a small-sized

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

that can reach a maximum length of 18 cm. Its body is compressed laterally with a rounded body profile, and its

snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, Rostrum (anatomy), rostrum, beak or proboscis. The wet furless surface around the nostrils of the n ...

protrudes forwards slightly with a small protrusible (extendable) mouth. Its very characteristic livery leaves no doubt about the identification. A dark brown-yellow area, the colour of which may vary in intensity, fully masks the head and extends to a line from the first rays of the

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

to the start of its

pelvic fins Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

. The rest of its body is white, peduncle and

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

included. Insertion of yellow-orange areas at the top of the side form a characteristic pyramidal pattern, hence the name of the fish. The

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

is also yellow-orange.

Distribution and habitat

The pyramid butterflyfish is widespread throughout the tropical and subtropical waters of the central

from Cocos Keeling and

Christmas Island Christmas Island, officially the Territory of Christmas Island, is an States and territories of Australia#External territories, Australian external territory in the Indian Ocean comprising the island of the same name. It is about south o ...

Polynesia Polynesia ( , ) is a subregion of Oceania, made up of more than 1,000 islands scattered over the central and southern Pacific Ocean. The indigenous people who inhabit the islands of Polynesia are called Polynesians. They have many things in ...

and from south

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

New-Caledonia New Caledonia ( ; ) is a group of islands in the southwest Pacific Ocean, southwest of Vanuatu and east of Australia. Located from Metropolitan France, it forms a ''sui generis'' collectivity of the French Republic, a legal status unique ...

. The pyramid butterflyfish appreciates the outer reef slopes from which it can swim out into open water to get its food. It can be seen at depths from 3 to 60 meters deep.

Biology

The pyramid butterflyfish lives in large

schools A school is the educational institution (and, in the case of in-person learning, the building) designed to provide learning environments for the teaching of students, usually under the direction of teachers. Most countries have systems of ...

, and feeds on

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

in open water out of its shelter

reef A reef is a ridge or shoal of rock, coral, or similar relatively stable material lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic (non-living) processes such as deposition (geol ...

.Randall, J.E., 1985. Guide to Hawaiian reef fishes. Harrowood Books, Newtown Square, PA 19073, USA. 74 p.

Conservation status

The species as a planktivorous could be affected by climate-induced reductions in planktonic productivity. There do not appear to be any current threats to this species and it is listed as Least Concern (LC) by the IUCN.

References

External links

* {{Taxonbar, from=Q2437382

Pyramid butterflyfish The pyramid butterflyfish (''Hemitaurichthys polylepis'') is a species of marine ray-finned fish, a butterflyfish belonging to the family Chaetodontidae, native from central Indo-Pacific. Description The pyramid butterflyfish is a small-sized f ...

Fish described in 1857