Ridgeheads, also known as
bigscales, are a
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
(
Melamphaidae, from the
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
melanos [black] and
amphi [by both sides]) of small, deep-sea stephanoberyciform
fishA fish is any aquatic vertebrate animal that is typically ectothermic , covered with scales, and equipped with two sets of paired fins and several unpaired fins...
. The family contains approximately 37
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
in five
generaIn 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:...
; their distribution is worldwide, but ridgeheads are absent from the
Arctic OceanThe Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest, and shallowest of the world's five major oceanic divisions.
The International Hydrographic Organization recognizes it as an ocean, although some...
and
Mediterranean SeaThe Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by Africa, and on the east by the Levant. The sea is technically a part of the Atlantic Ocean, although it...
. Although the family is one of the most widespread and plentiful of deep-sea families, none of its members are of interest to commercial
fisheryGenerally, a fishery is an entity engaged in raising and/or harvesting fish, which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of...
.
These fish are named for their large
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 and pronounced cranial ridges, as well as for their typically dark brown to black coloration.
Ridgeheads, also known as
bigscales, are a
familyIn biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus...
(
Melamphaidae, from the
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
melanos [black] and
amphi [by both sides]) of small, deep-sea stephanoberyciform
fishA fish is any aquatic vertebrate animal that is typically ectothermic , covered with scales, and equipped with two sets of paired fins and several unpaired fins...
. The family contains approximately 37
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
in five
generaIn 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:...
; their distribution is worldwide, but ridgeheads are absent from the
Arctic OceanThe Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest, and shallowest of the world's five major oceanic divisions.
The International Hydrographic Organization recognizes it as an ocean, although some...
and
Mediterranean SeaThe Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by Africa, and on the east by the Levant. The sea is technically a part of the Atlantic Ocean, although it...
. Although the family is one of the most widespread and plentiful of deep-sea families, none of its members are of interest to commercial
fisheryGenerally, a fishery is an entity engaged in raising and/or harvesting fish, which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of...
.
These fish are named for their large
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 and pronounced cranial ridges, as well as for their typically dark brown to black coloration. Ridgeheads are the largest and most diverse family of their
orderIn scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
.
Physical description
Typical of the Stephanoberyciformes, the melamphid body is robust, oblong, subcylindrical, and slightly compressed laterally. The head is large and scaleless, with its profile either bluntly rounded or with a sharp frontal angle; it is conspicuous for its prominent ridges, which are covered by thin
skinThe skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system made up of multiple layers of mesodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs. Skin of a different nature exists in amphibians, reptiles, birds...
. The head is also cavernous, being riddled by
muciferousIn vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. It is a viscous colloid containing antiseptic enzymes and immunoglobulins that serves to protect epithelial cells in the respiratory,...
canals—similar structures are found in the beryciform
slimeheadSlimeheads, also known as roughies and redfish, are mostly small, exceptionally long-lived, deep-sea beryciform fish constituting the family Trachichthyidae...
(Trachichthyidae) and
fangtoothFangtooths are deep-sea, ferocious-looking beryciform fish of the family Anoplogastridae . With a circumglobal distribution in tropical and cold-temperate waters, the family contains only two very similar species, in one genus, with no known close relatives: the common fangtooth, Anoplogaster...
(Anoplogastridae) families. Sharp
spinesIn biology, spine or spiny may refer to:*Spine , needle-like structures in plants*Spine , needle-like structures in animalsSpine may also refer to:*Vertebral column, spine in anatomy, the backbone...
and serrations may further adorn the head in some species. The mouth is large and oblique; the long
jawThe jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...
s extend to or exceed the posterior margin of the
eyeEyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system...
, and are lined with villiform (brushlike)
teethTeeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to tear, scrape, and chew food. Some animals, particularly carnivores, also use teeth for hunting or defense. The roots of teeth are covered by gums...
. The
vomerThe vomer is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones.-Biology:...
,
palatinesThe palatine bone is a bone in many species of the animal kingdom, commonly termed the palatum .-Human anatomy:...
, endopterygiod, and ectopterygiods all lack teeth. The
eyeEyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system...
s are usually fairly small, but in
Poromitra megalops they may exceed 20 per cent of the head's length in diameter.
The large scales are cycloid and imbricate; they are arranged in a longitudinal series of 12–40. Usually deciduous, these scales are largest in
Scopelogadus species; in these and some other species, the scales'
circuli (concentric lines) are clearly visible to the unaided eye. The
lateral lineIn aquatic organisms , the lateral line is a sense organ used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
(excluding the network of cranial canals) is largely absent; when present, it is reduced to 1–2 pored scales following the
operculumThe operculum of a bony fish is the hard bony flap covering and protecting the gills. In most fish, the rear edge of the operculum roughly marks the division between the head and the body. The operculum is composed of four fused bones; the opercle, preopercle, interopercle, and subopercle...
's upper edge. The caudal peduncle is relatively long; the caudal fin is forked to emarginate and possesses 3–4 procurrent spines. The single
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...
originates behind the pectoral and pelvic fins and contains 1–3 weak spines and 9–18 soft rays; the pectoral fins are elongate and tapered (the superior rays being longer than the inferior rays) and contain 12–16 soft rays. The pelvic fins are thoracic to subthoracic with one spine and 6–8 soft rays; the anal fin is small and set far back, with one spine and 7–11 soft rays.
The branchiostegal rays number 7–8 and the
vertebraA vertebra is an individual bone in the flexible column that defines vertebrate animals, e.g. humans. The vertebral column encases and protects the spinal cord, which runs from the base of the cranium down the dorsal side of the animal until reaching the pelvis. From there, vertebra continue into...
e 24–31. The largest species recorded is the crested bigscale (
Poromitra crassiceps) at up to 18 centimetres standard length (SL; a measurement excluding the caudal fin). Most ridgeheads are well under 10 centimetres SL.
Life history
Ridgeheads are meso- to
bathypelagicAny water in the sea that is not close to the bottom is in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means open sea....
; they have been trawled at depths as shallow as to as deep as . Some species undergo
diel vertical migrationDiel vertical migration refers to a pattern of movement that some organisms living in the ocean's photic zone undertake each day. The word diel comes from the Latin dies , and means a 24-hour period....
s of several hundred metres; that is, they remain at aphotic depths (below ca. 400 metres) during the day but rise to surface waters (10–100 metres) at night to feed and (presumably) to avoid predators. Ridgeheads feed primarily on
zooplanktonZooplankton are the heterotrophic type of plankton. Plankton are organisms drifting in the water column of oceans, seas, and bodies of fresh water. The name of zooplankton is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
, such as
copepodCopepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Many species are planktonic , but more are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s, euphausiids, and other small pelagic
crustaceanCrustaceans are a very large group of arthropods, comprising almost 52,000 described species , and are usually treated as a subphylum . They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles...
s. There is also a marked segregation of life stages:
larvaA larva is a young form of animal with indirect development, going through or undergoing metamorphosis ....
l and juvenile ridgeheads are present within the upper 200 metres of the water column, whereas adults are typically found much farther down.
The family is sometimes termed
pseudoceanic because, rather than having an even distribution in open water, ridgeheads occur in significantly higher abundances around structural oases, notably
seamountA seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface , and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of 1,000–4,000 meters depth...
s and over continental slopes. This is also true of other deep-sea pelagic groups, such as the
lanternfishLanternfishes are small, deep sea fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, and are found in oceans worldwide. They are aptly named after their conspicuous use of bioluminescence...
(Myctophidae),
marine hatchetfishThe 'marine hatchetfishes or deep-sea hatchetfishes are small deep-sea bathypelagic ray-finned fish of the stomiiform subfamily Sternoptychinae...
(Sternoptychidae), and
lightfishLightfishes are small stomiiform fishes in the family PhosichthyidaeThey are very small fishes found in oceans throughout the world: most species grow no longer than 10 cm, while those in the genus Vinciguerria only reach 4 cm or so....
(Phosichthyidae or Photichthyidae) families. The phenomenon is explained by the likewise abundance of prey species which are also attracted to the structures.
As oviparous pelagic
spawnersSpawning is the production or depositing of large quantities of eggs in water. The process is done by aquatic animals such as amphibians and fish.- Types of egg-layers :*egg scatterers*nest builders*egg hangers*mouth breeders*egg buriers...
, ridgeheads produce many tiny
eggsRoe or hard roe is the fully ripe internal ovaries or egg masses of fish and certain marine animals, such as shrimp, scallop and sea urchins...
which are fertilized externally; the eggs and larvae (and early juveniles) are buoyant and
planktonPlankton consist of any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. Plankton are defined by their ecological niche rather than their phylogenetic or taxonomic classification...
ic, drifting with the currents near the surface until the juveniles have reached the point where they are strong enough to determine their own direction. Study of the spawning habits of twospine bigscales (
Scopelogadus mizolepis bispinosus) indicates spawning occurs year-round, with no definite peaks.
Although their deep-living nature protects them from predation to some degree, ridgeheads are prey to large
seabirdSeabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s such as
albatrossAlbatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes . They range widely in the Southern Ocean and the North Pacific...
es; large
squidSquid are marine cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms and two longer tentacles arranged in pairs...
such as the Jumbo Squid (
Dosidicus gigas) and Sevenstar Flying Squid (
Martialia hyadesii);
oceanic dolphinOceanic dolphins are the members of the Delphinidae family of cetaceans. These aquatic mammals are related to whales and porpoises. They are found worldwide, mostly in the shallower seas of the continental shelves...
s (family Delphinidae); and large
pelagic fishPelagic fish live in the water column of coastal, ocean and lake waters, but not on the bottom of the sea or the lake. They can be contrasted with demersal fish, which do live on or near the bottom, and reef fish which are associated with coral reefs....
, such as
tunaTuna are ocean-dwelling carnivorous fish in the family Scombridae, mostly in the genus Thunnus. Tuna are fast swimmers—they have been clocked at —and include several warm-blooded species...
and other
scombridScombridae is the family of the mackerels, tunas, and bonitos, and thus includes many of the most important and familiar food fishes. The family consists of about 55 species in 15 genera and two subfamilies...
s.
Species
There are 37 species in five genera:
- Genus Melamphaes
- Slender bigscale, Melamphaes acanthomus Ebeling, 1962.
- Melamphaes danae Ebeling, 1962.
- Melamphaes ebelingi Keene, 1973.
- Melamphaes eulepis Ebeling, 1962.
- Melamphaes hubbsi Ebeling, 1962.
- Melamphaes indicus Ebeling, 1962.
- Melamphaes janae Ebeling, 1962.
- Melamphaes laeviceps Ebeling, 1962.
- Melamphaes leprus Ebeling, 1962.
- Melamphaes longivelis Parr, 1933.
- Highsnout melamphid, Melamphaes lugubris Gilbert, 1891.
- Melamphaes macrocephalus Parr, 1931.
- Melamphaes microps
Melamphaes microps is a fish of the genus Melamphaes, found in the North Atlantic, South Atlantic, southern Indian Ocean, and the south west Pacific including New Zealand, at depths of from 1,000 to 3,000 m...
(Günther, 1878).
- Melamphaes parini Kotlyar, 1999.
- Little bigscale, Melamphaes parvus Ebeling, 1962.
- Melamphaes polylepis Ebeling, 1962.
- Melamphaes pumilus Ebeling, 1962.
- Ridgehead, Melamphaes simus Ebeling, 1962.
- Melamphaes spinifer Ebeling, 1962.
- Melamphaes suborbitalis (Gill
Theodore Nicholas Gill was an American ichthyologist, mammalogist, malacologist and librarian.Born and educated in New York City under private tutors, Gill early showed interest in natural history. He was associated with J...
, 1883).
- Melamphaes typhlops (Lowe, 1843).
- Genus Poromitra
- Poromitra capito Goode & Bean, 1883.
- Poromitra crassa Parin & Ebeling, 1980.
- Crested bigscale, Poromitra crassiceps (Günther, 1878).
- Poromitra gibbsi Parin & Borodulina, 1989.
- Poromitra megalops (Lütken, 1877).
- Yawning
The yawning, Poromitra oscitans, is a fish of the family Melamphaidae, found in tropical and subtropical waters of the indo-Pacific region.-References:...
, Poromitra oscitans Ebeling, 1975.
- Poromitra unicornis (Gilbert, 1905).
- Genus Scopeloberyx
- Scopeloberyx microlepis (Norman, 1937).
- Scopeloberyx opisthopterus (Parr, 1933).
- Longjaw bigscale, Scopeloberyx robustus (Günther, 1887).
- Scopeloberyx rubriventer (Koefoed, 1953).
- Genus Scopelogadus
- Scopelogadus beanii (Günther, 1887).
- Twospine bigscale, Scopelogadus mizolepis bispinosus (Gilbert, 1915).
- Scopelogadus mizolepis mizolepis Günther, 1878.
- Scopelogadus unispinis Ebeling & Weed, 1963.
- Genus Sio
- Sio nordenskjoldii (Lönnberg, 1905).