The 'marine hatchetfish
es or
deep-sea hatchetfishes are small deep-sea bathypelagic ray-finned fish of the stomiiform subfamily
Sternoptychinae. They should not be confused with the
freshwater hatchetfishThe freshwater hatchetfishes are a family, Gasteropelecidae, of ray-finned fish. The common hatchetfish is the most popular member among fish keeping hobbyists...
es, which are not particularly closely related
TeleosteiTeleostei is one of three infraclasses in class Actinopterygii, the ray-finned fishes. This diverse group, which arose in the Triassic period, includes 20,000 extant species in about 40 orders; most living fishes are members of this group...
in the characiform family Gasteropelecidae.
The scientific name means "
Sternoptyx-subfamily", from
SternoptyxSternoptyx 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.It contains only four living species:...
(the
type genusIn biology, the phrase type genus is used differently depending on the nomenclatural Code that applies:* In zoological nomenclature, a type genus is "The nominal genus that is the name-bearing type of a nominal family-group taxon."...
) + the standard
animalAnimals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...
family
suffixIn grammar, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns or adjectives, and verb endings, which form the conjugation of verbs...
"-inae".
The 'marine hatchetfish
es or
deep-sea hatchetfishes are small deep-sea bathypelagic ray-finned fish of the stomiiform subfamily
Sternoptychinae. They should not be confused with the
freshwater hatchetfishThe freshwater hatchetfishes are a family, Gasteropelecidae, of ray-finned fish. The common hatchetfish is the most popular member among fish keeping hobbyists...
es, which are not particularly closely related
TeleosteiTeleostei is one of three infraclasses in class Actinopterygii, the ray-finned fishes. This diverse group, which arose in the Triassic period, includes 20,000 extant species in about 40 orders; most living fishes are members of this group...
in the characiform family Gasteropelecidae.
The scientific name means "
Sternoptyx-subfamily", from
SternoptyxSternoptyx 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.It contains only four living species:...
(the
type genusIn biology, the phrase type genus is used differently depending on the nomenclatural Code that applies:* In zoological nomenclature, a type genus is "The nominal genus that is the name-bearing type of a nominal family-group taxon."...
) + the standard
animalAnimals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...
family
suffixIn grammar, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns or adjectives, and verb endings, which form the conjugation of verbs...
"-inae". It ultimately derives from
Ancient GreekAncient Greek is the historical stage in the development of the Greek language spanning across the Archaic , Classical , and Hellenistic periods of ancient Greece and the ancient world. It is predated in the 2nd millennium BC by Mycenaean Greek...
stérnon (στέρνον, "breast") +
ptýx (πτύξ, "a fold/crease") +
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. Through the Roman conquest, Latin spread throughout the Mediterranean and a large part of Europe...
forma ("external form"), the Greek part in reference to the
thoraxThe thorax is a division of an animal's body that lies between the head and the abdomen.In mammals, the thorax is the region of the body formed by the sternum, the thoracic vertebrae and the ribs. It extends from the neck to the diaphragm, and does not include the upper limbs. The heart and the...
shape of marine hatchetfishes.
Description and ecology
Found in tropical and subtropical waters of the
AtlanticThe Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about 106.4 million square kilometres , it covers approximately one-fifth of the Earth's surface and about one-quarter of its water surface area. The first part of its name refers to the Atlas of Greek...
,
PacificThe Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Tepre Pacificum, "peaceful sea", bestowed upon it by the Portuguese explorer Ferdinand Magellan. It extends from the Arctic in the north to Antarctica in the south, bounded by Asia and...
and
Indian OceanThe Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by South Asia ; on the west by Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean...
s, marine hatchetfishes range in size from
Polyipnus danae at to the c.-long
Giant HatchetfishThe Giant Hatchetfish or Greater Silver Hatchetfish a marine hatchetfish of the genus Argyropelecus, is found in every ocean except the north Pacific in deep tropical and subtropical waters.-References:...
(
Argyropelecus gigas). They are small deep-sea fishes which have evolved a peculiar body shape and like their relatives have bioluminescent
photophoreA photophore is a light-emitting organ which 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...
s. The latter allow them to use counterillumination to escape predators that lurk in the depths: by matching the light intensity with the light penetrating the water from above, the fish does not appear darker if seen from below. They typically occur at a few hundred meters below the surface, but their entire depth range spans from 50 to 1,500 meters deep.
The body is deep and
lateralStandard anatomical terms of location are employed in science which deal with the anatomy of animals to avoid ambiguities which might otherwise arise. They are not language-specific, and thus require no translation...
ly extremely compressed, somewhat resembling a
hatchetA hatchet is a single-handed striking tool with a sharp blade used to cut and split wood...
(with the
thoraxThe thorax is a division of an animal's body that lies between the head and the abdomen.In mammals, the thorax is the region of the body formed by the sternum, the thoracic vertebrae and the ribs. It extends from the neck to the diaphragm, and does not include the upper limbs. The heart and the...
being the "blade" and the caudal peduncle being the "handle"). The
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
PolyipnusPolyipnus is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. This is the largest genus of the marine hatchetfishes and indeed of the entire Sternoptychidae...
is rounded, the other two – in particular
SternoptyxSternoptyx 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.It contains only four living species:...
– decidedly angular if seen from the side. Their
pelvisIn human anatomy, the pelvis is the part of the trunk inferioposterior to the abdomen in the transition area between the trunk and the lower limbs...
is rotated to a
verticalAn object is in a vertical position when it is aligned in an "up-down" direction, roughly speaking perpendicular to the horizon or horizontal plane.In science, it can also refer to:...
position. The mouth is located at the tip of the snout and directed almost straight downwards.
Their
scaleIn most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
s are silvery, delicate and easily abraded. In some species, such as the Highlight Hatchetfish (
Sternoptyx pseudobscura), large sections of the body at the base of the anal fin and/or caudal fin are transparent. They have preopercular spines and blade-like pterygiophores in front of the
dorsal finA dorsal fin is a fin located on the backs of some fish, whales, dolphins, and porpoises, as well as the ichthyosaurs. Depending on the species, an animal can have up to three of them. Its main purpose is to stabilize the animal against rolling and assist in sudden turns...
. The anal fin has 11-19 rays and in some
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
is divided in two parts; almost all have an adipose fin. Their large, sometimes tube-shaped eyes can collect the faintest of light and
focusFocus or FOCUS may refer to:In science, mathematics or computing:*Focus , a point toward which light rays are made to converge*Focus , an earthquake's underground point of origin or hypocenter...
well on objects both close and far. They are directed somewhat upwards, most conspicuously in the genus
ArgyropelecusArgyropelecus is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. A collective name is "silver hatchetfishes", but this can also refer to a species of the freshwater hatchetfishes which are not particularly closely related but merely convergent...
. This allows to discern the
silhouetteA silhouette is a view of an object or scene consisting of the outline and a featureless interior, with the silhouetted object usually being black...
s of prey moving overhead against the slightly brighter upper waters.
Genera
There are three genera in this subfamily, with some 40
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
altogether:
- Argyropelecus
Argyropelecus is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. A collective name is "silver hatchetfishes", but this can also refer to a species of the freshwater hatchetfishes which are not particularly closely related but merely convergent...
– silver hatchetfishes (7 species)
- Polyipnus
Polyipnus is an oceanic ray-finned fish genus which belongs in the family Sternoptychidae. This is the largest genus of the marine hatchetfishes and indeed of the entire Sternoptychidae...
(32 species)
- 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.It contains only four living species:...
(4 species)