''Sternoptyx diaphana'', the diaphanous hatchetfish, is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of deep sea

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Sternoptychidae. It is the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

of the genus ''

Sternoptyx ''Sternoptyx'' is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. This is the type genus of the Sternoptychidae, as well as the marine hatchetfish subfamily Sternoptychinae. ''Sternoptyx'' have silvery, high, and ...

'', and was first described by the French naturalist Johann Hermann in ''

Der Naturforscher ''Der Naturforscher'' ( "The Naturalist") was a German scientific publication of the Enlightenment devoted to natural history. It was published yearly from 1774 to 1804, by J. J. Gebauers Witwe and Joh. Jac. Gebauer at Halle and edited first ...

'' 1781.

Description

''Sternoptyx diaphana'' is a short, deep-bodied fish with a laterally compressed body and a maximum length of about . The mouth is nearly vertical, the snout is short and the eyes are large. The body slopes steeply up from the head and levels off at the caudal peduncle. In front of the dorsal fin is a toothed, pear-shaped translucent plate supported by a single spine. The dorsal fin has 9 to 12 soft rays and the anal fin 13 to 14. There is a translucent fold of skin just below the short tail, and another below the ventral region of the body. There are photophores behind and below the eye, on the gill cover, and rows of photophores on the underside of the fish. The dorsal region is dark, the flanks are silvery and the fins transparent.

Distribution and habitat

''Sternoptyx diaphana'' has a wide distribution in temperate and tropical waters of all the world's oceans, although occurring with less frequency in equatorial seas. Its depth range is , but it is most often found between about , where the water temperature is between . It appears not to make the daily vertical migrations made by some related species.

Ecology

The diet consists of small fish,

euphausiids Krill are small crustaceans of the order Euphausiacea, and are found in all the world's oceans. The name "krill" comes from the Norwegian word ', meaning "small fry of fish", which is also often attributed to species of fish. Krill are consi ...

, decapods,

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

s and amphipods. Larger fish generally consume larger food items; the diet varies with location with the fish appearing to be opportunistic predators of whatever prey species they encounter.

Status

''Sternoptyx diaphana'' has a very wide distribution, is a common species and faces no particular threats. For these reasons, the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

has assessed its conservation status as being of "

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

References

{{Taxonbar, from=Q659253 Sternoptychidae Fish described in 1781 Taxa named by Johann Hermann