''Anoplogaster cornuta'', the common fangtooth, 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 deep sea fish found in temperate and tropical oceans worldwide. It is found at depths of from with the adults usually found from and the young usually found near the surface. This species grows to a

total length Fish measurement is the measuring of individual fish and various parts of their anatomies, for data used in many areas of ichthyology, including taxonomy and fishery biology. Overall length Standard length (SL) is the length of a fish measured f ...

of about . While a source of food for

pelagic The pelagic zone consists of the water column of the open ocean and can be further divided into regions by depth. The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the sur ...

carnivorous fishes, this species is of no interest for human

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life or, more commonly, the site where such enterprise takes place ( a.k.a., fishing grounds). Commercial fisheries include wild fisheries and fish farm ...

Description

The common fangtooth has a distinctive appearance and grows to a total length of about . Adults are dark brown to black, the head is very large, bony and finely sculptured but does not bear any spines. The eye is small and the gill rakers have bony bases and are tooth-like. The body is deepest just behind the head, tapering rapidly to the caudal peduncle. The mouth is well-armed with sharp fangs and the skin is granular. The dorsal fin has no spines and 17 to 20 soft rays while the anal fin has no spines and 7 to 9 soft rays. The lateral line takes the form of an open groove, bridged in places by overlapping scales. Many deep sea fish do not have

swim bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ (anatomy), organ in bony fish that functions to modulate buoyancy, and thus allowing the fish to stay at desired water depth without having to maintain lift ...

s, but the common fangtooth does. Juveniles look very different from adults, so much so that they were at one time believed to be a different species. The juveniles were first described as ''Anoplogaster cornuta'' by the French zoologist

Achille Valenciennes Achille Valenciennes (9 August 1794 – 13 April 1865) was a French zoology, zoologist. Valenciennes was born in Paris, and studied under Georges Cuvier. His study of parasitic worms in humans made an important contribution to the study of parasi ...

in 1833, and it was fifty years later that the adults were described and given the name ''Caulolepis longidens''. Not until 1955 was it appreciated that the two were the same species. The juveniles are a much paler colour and somewhat triangular in cross section. They have several long spines on the head, large eyes and slender, pointed gill rakers, but have small teeth and lack the fangs of the adult fish. The skin is largely unpigmented and clad in unpigmented scales, but there is a black patch on the belly formed by dark-coloured cup-like scales. As the juvenile reaches adulthood, it becomes darker as black scales grow to cover its still-unpigmented skin.

Distribution and habitat

The common fangtooth has a global distribution being found in tropical and temperate waters in both the eastern and western Atlantic Ocean, the Indian Ocean and the Pacific Ocean. Off the western seaboard of America its range extends from British Columbia southwards to south of the equator. It is a

fish occurring between , with adults between ; adults occur in deep water and are often caught in trawls at about . Juveniles are found at lesser depths.

Behaviour

The common fangtooth is a predator and feeds on other fish,

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s and

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

s. They are themselves preyed on by such fish as

tuna A tuna (: tunas or tuna) is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bul ...

marlin Marlins are fish from the family Istiophoridae, which includes between 9 and 11 species, depending on the taxonomic authority. Name The family's common name is thought to derive from their resemblance to a sailor's marlinspike. Taxonomy T ...

and

albacore The albacore (''Thunnus alalunga''), known also as the longfin tuna, is a species of tuna of the order Scombriformes. It is found in temperate and tropical waters across the globe in the epipelagic and mesopelagic zones. There are six distinct ...

. It is a schooling fish and is often found in small groups, though it may be solitary. Off the west coast of North America, the common fangtooth seems to breed in the summer months. The fish are

oviparous Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...

and the developing larvae are

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 ...

ic. From examination of the

otolith An otolith (, ' ear + , ', a stone), also called otoconium, statolith, or statoconium, is a calcium carbonate structure in the saccule or utricle (ear), utricle of the inner ear, specifically in the vestibular system of vertebrates. The saccule ...

s (bony structures behind the eyes), it appears that this fish lives for at least three years.

Research

These fish were tested to see how pressure affects their respiration as compared to other fish. Researchers found that these fish are able to regulate their respiratory system according to their environment and that the respiration rate was directly proportional to the size of the fish. Although almost no light penetrates to the deep sea from the surface, the common fangtooth has evolved features that make it practically invisible. Like other deep sea fish, it needs to avoid being seen by predators, some of which hunt for prey by creating their own light by means of

bioluminescence Bioluminescence is the emission of light during a chemiluminescence reaction by living organisms. Bioluminescence occurs in multifarious organisms ranging from marine vertebrates and invertebrates, as well as in some Fungus, fungi, microorgani ...

. The common fangtooth achieves invisibility by absorbing light with great efficiency. The pigment

melanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...

is crammed into granules which are grouped into

melanophores Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast ...

which cover virtually the whole of the

dermis The dermis or corium is a layer of skin between the epidermis (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from s ...

. This absorbs almost all of the incoming light, and any remaining light that scatters sideways is absorbed by neighbouring granules. Altogether, the absorption of light is 99.5% efficient, a fact that makes photographing this fish in its natural habitat very difficult.

References

{{Taxonbar, from=Q1885885 Cosmopolitan fish Anoplogastridae Marine fish of Nicaragua Fish described in 1833 Taxa named by Achille Valenciennes