The pineapplefish (''Cleidopus gloriamaris'') also known as the Mailfish is a species of

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

in the family

Monocentridae Pinecone fishes are small and unusual marine fish of the family ''Monocentridae''. The family contains just four species in two genera, one of which is monotypic. Their distribution is limited to tropical and subtropical waters of the Indo-Pac ...

, and the sole member of its genus. It is also known as the knightfish or the coat-of-mail fish, due to the armor-like scales covering its body, and the port-and-starboard light fish, as it has a pair of bioluminescent organs that are reminiscent of

navigation light A navigation light, also known as a running or position light, is a source of illumination on a watercraft, aircraft or spacecraft, meant to give information on the craft's position, heading, or status. Some navigation lights are colour-coded r ...

s on ships. Its

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

is from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

and ', meaning "glory of the sea".

Distribution and habitat

The pineapplefish is native to coastal waters off

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

, and

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

. It occurs at a depth of in

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 processes— deposition of sand, wave erosion planing down rock out ...

s and

harbors A harbor (American English), harbour (British English; see spelling differences), or haven is a sheltered body of water where ships, boats, and barges can be docked. The term ''harbor'' is often used interchangeably with ''port'', which is a ...

Description

The pineapplefish grows up to long. It has a plump, rounded body almost completely covered in large, rough scales with sharp, backward-pointing spines. The head is large, with

mucous Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It is ...

pits bordered by rough ridges, and is armored with heavy bone. The snout is blunt and overhangs the wide

mouth In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...

. The

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

are tiny and thin, present on the jaws, palatine, and vomer. There are two pits containing

bioluminescent Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some Fungus, fungi, microorganisms including ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

on the

lower jaw In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

near the corners of the

, which are concealed when the mouth is closed. This

photophore A photophore is a glandular organ that appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors, ...

is green in young fish and becomes more red as it ages.McGrouther, M. (November 2004
Pineapplefish, ''Cleidopus gloriamaris''
''Australiam Museum Fish Site''. Retrieved on March 13, 2009. The first

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

consists of 5–7 strong spines; the spines are free of a membrane and point alternatingly left and right. The second dorsal fin contains 12

soft rays Fish anatomy is the study of the form or morphology of fish. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology co ...

. Each

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

contains an extremely large spine, nearly as long as the head, and 3–4 rudimentary rays. The pelvic spine can be locked erect at a right angle to the body. The

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

contains 11–12 rays and the

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s 14–15 rays. The scales of the pineapplefish are yellow to whitish with black rear margins, forming the striking pattern that gives this fish its name. The lips, chin, and parts of the jaw are black. There is a red stripe on the lower jaw running to the photophore. This species is very similar to the pinecone fishes of the genus ''

Monocentris ''Monocentris'' is a genus of pinecone fishes native to the Indian Ocean, Indian and Pacific Oceans. Species There are currently four recognized species in this genus: * ''Monocentris chrysadamas'' (Yo Su, Hsiu-Chin Lin, and Hsuan-Ching Ho, 2022 ...

'', and is placed within that genus by some authors. ''Cleidopus'' differs from ''Monocentris'' in having a narrow preorbital bone and in the position of its light organs, which are near the tip of the lower jaw in ''Monocentris''. This species also differs from the Japanese pineapplefish (''Monocentris japonica'') in having a more rounded snout.

Biology and ecology

Due to its small fins and rigid armor, the pineapplefish is a weak swimmer. A

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

species, it may be found inside caves and under rocky ledges during the day. In the Fly Point Halifax Park Aquatic Preserve,

, a small group of pineapplefish has been documented under the same ledge for at least seven years, and another group under a different ledge for three years.Harasti, D
Pineapple Fish (''Cleidopus gloriamaris'')
''The Underwater Photo Gallery - Dave Harasti''. Retrieved on March 13, 2009. At night, this species ventures out onto sandy flats to feed, using its light organs to illuminate small

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

. The light may also be used to communicate with conspecifics. The light of the pineapplefish is produced by

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

colonies of the bacteria ''

Vibrio fischeri ''Aliivibrio fischeri'' (also called ''Vibrio fischeri'') is a Gram-negative, rod-shaped bacterium found globally in marine environments. This species has bioluminescent properties, and is found predominantly in symbiosis with various marine anim ...

'' within its photophores. ''V. fischeri'' are also found free-living in sea water and are naturally released from the pineapplefish's photophores. However, their luminescence dims within a matter of hours after being released. This species has lived up to 10 years in captivity.

Relationship to humans

The pineapplefish is moderately common in deep water, but due to its retiring nature, for some time after its initial discovery it was only known from specimens tossed ashore by storms. This fish is sometimes collected by commercial trawlers, and is popular with saltwater fish aquarists. It is fairly hardy, but must be provided with rocky hiding places and live food. The species is not targeted by any fisheries, but is often taken as

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

by commercial trawlers.

References

{{Taxonbar, from=Q1758490 Monocentridae Taxa named by Charles Walter De Vis Bioluminescent fish Marine fish of Eastern Australia Marine fish of Western Australia Fish described in 1882

Cleidopus The pineapplefish (''Cleidopus gloriamaris'') also known as the Mailfish is a species of fish in the family Monocentridae, and the sole member of its genus. It is also known as the knightfish or the coat-of-mail fish, due to the armor-like scale ...