Lasiognathus
Encyclopedia
Lasiognathus is a genus
of deep-sea
anglerfish
in the family Thaumatichthyidae, with five species
known from the Atlantic
and Pacific Ocean
s. It has been called a "compleat angler", in that its lure apparatus consists of a fishing rod
(the projecting basal bone or pteropterygium), a fishing line
(the illicium, a modified dorsal fin
ray
), bait
(the bioluminescent
esca), and hook
s (large dermal denticle
s). It is also distinctive for an enormous upper jaw
with premaxillaries
that can be folded down to enclose the much shorter lower jaw
.
, which also has enlarged and hinged premaxillaries
, escal denticles, and a branched upper operculum
. However, there are significant differences between those two taxa
as well, which includes characters that Lasiognathus shares with the oneirodids
not found in Thaumatichthys. Bertelsen and Struhsaker (1977) noted that, given the undefined cladistics
of the Oneirodidae, it was somewhat subjective
whether Lasiognathus and Thaumatichthys were placed in their own family, in separate families, or in the Oneirodidae. comes from the Ancient Greek
, meaning "hairy", and , meaning "jaw".
and Pacific Ocean
s. L. beebei is known from the north Atlantic and off Oahu
in Hawaiian Islands
. L. waltoni is known from the central Pacific, just north of Oahu. L. intermedius is known from the western north Atlantic, the eastern south Pacific, and from off Cape Town, South Africa
. L. saccostoma is known from the north Atlantic and off the Hawaiian Islands. L. amphirhamphus is known from off the Madeira Islands
in the eastern north Atlantic. Lasiognathus specimens of uncertain species are also known from the north Pacific and the South China Sea
. They are pelagic
in nature, occurring to a depth of 4,000 m.
female Lasiognathus have been collected; there is presumably extreme sexual dimorphism
in size and shape as with other deep-sea anglerfishes. These fishes have a slender body
with a large, slender head
measuring over 60% of the standard length
. The mouth
is huge, with the premaxillaries
of the upper jaw
enlarged and extending well beyond the short lower jaw
. The premaxillaries are separated anteriorly and connected by a broad elastic
membrane
, and are hinged with the upper jaw so that they are able to flip up and down. When in the latter position, the premaxillaries completely enclose the lower jaw. There are numerous long, hooked teeth placed in roughly oblique rows on the premaxillaries.
The pterygiophore (the basal bone supporting the illicium) of Lasiognathus is unusually long amongst anglerfish, measuring some 85% of the standard length. This bone inserts dorsally on the head and is capable of sliding forwards and backwards within a trough that extends the full length of the cranium and between the epaxial musculature on the front half of the body. The illicium is also long, with a terminal esca and 2-3 bony hook-shaped denticles mounted on an appendage at the tip. The escal bulb is equipped with a flap of skin that allows adjustment of the emitted light. The sphenotic spines (above the eyes) are well-developed, as are the two articular spines (at the rear end of the lower jaw). The operculum
is divided into two parts, with the dorsal part split into two (rarely three) branches.
The pectoral fin lobe is small, short, and broad; the fin ray
s number 5 in the dorsal fin
, 5 in the anal fin, 14-20 in the pectoral fins, and 9 in the caudal fin. The skin
is entirely naked, without spines or denticles. The coloration is a deep chocolate brown. All Lasiognathus are small fishes; L. amphirhamphus is the largest known species at 15.7 cm standard length
. L. beebei attains a maximum length of 11.5 cm, L. intermedius 12.9 cm, L. saccostoma 7.7 cm, and L. waltoni 9.4 cm.
speculated in 1930 that the fishing apparatus of Lasiognathus might "be cast swiftly ahead, when then the hooks and the lights would so frighten any pursued fish that they would hesitate long enough to be engulfed in the onrushing maw," though Richard Ellis
considered this scenario unlikely. Nolan and Rosenblatt (1975) echoed Beebe's skepticism that the hooks were actually used to hook prey, though they proposed that "squid
tentacle
s could conceivably be impaled on the hooks and the prey thus secured". It has also been proposed that Lasiognathus might form its mouth into a sort of sieve
for filter feeding. More likely, prey is simply attracted by the glowing esca to within range of the jaws.
Stomach
contents reveal that Lasiognathus feeds primarily on bony fishes, such as lanternfish
es and bristlemouths, and occasionally takes invertebrate
s including copepod
s, amphipods, mysid shrimps, siphonophores, salp
s, pteropods, and chaetognaths. It is not known whether the males are parasitic; neither males nor larvae have yet been collected.
of the esca:
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of deep-sea
Deep sea
The deep sea, or deep layer, is the lowest layer in the ocean, existing below the thermocline and above the seabed, at a depth of 1000 fathoms or more. Little or no light penetrates this part of the ocean and most of the organisms that live there rely for subsistence on falling organic matter...
anglerfish
Anglerfish
Anglerfishes are members of the teleost order Lophiiformes . They are bony fishes named for their characteristic mode of predation, wherein a fleshy growth from the fish's head acts as a lure; this is considered analogous to angling.Some anglerfishes are pelagic , while others are benthic...
in the family Thaumatichthyidae, with five species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
known from the Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
and Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
s. It has been called a "compleat angler", in that its lure apparatus consists of a fishing rod
Fishing rod
A fishing rod or a fishing pole is a tool used to catch fish, usually in conjunction with the pastime of angling, and can also be used in competition casting. . A length of fishing line is attached to a long, flexible rod or pole: one end terminates in a hook for catching the fish...
(the projecting basal bone or pteropterygium), a fishing line
Fishing line
A fishing line is a cord used or made for angling. Important parameters of a fishing line are its length, material, and weight...
(the illicium, a modified dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
ray
Fish anatomy
Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does.- Body :...
), bait
Fishing bait
Fishing bait is any substance used to attract and catch fish, e.g. on the end of a fishing hook, or inside a fish trap. Traditionally, nightcrawlers, insects, and smaller bait fish have been used for this purpose...
(the bioluminescent
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
esca), and hook
Fish hook
A fish hook is a device for catching fish either by impaling them in the mouth or, more rarely, by snagging the body of the fish. Fish hooks have been employed for centuries by fishermen to catch fresh and saltwater fish. In 2005, the fish hook was chosen by Forbes as one of the top twenty tools...
s (large dermal denticle
Fish scale
Fish scale may refer to:* The rigid plates on the skin of a fish* Fishscale, an album by Ghostface Killah* Fishscale cocaine* Fish Scales, a rapper...
s). It is also distinctive for an enormous upper jaw
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
with premaxillaries
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
that can be folded down to enclose the much shorter lower jaw
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
.
Systematics
The closest relative of Lasiognathus is ThaumatichthysThaumatichthys
Thaumatichthys is a genus of deep-sea anglerfish in the family Thaumatichthyidae, with three known species. Its scientific name means "wonder-fish" in Greek; oceanographer Anton Bruun described these fishes as "altogether one of the oddest creatures in the teeming variety of the fish world." In...
, which also has enlarged and hinged premaxillaries
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
, escal denticles, and a branched upper operculum
Operculum (fish)
The 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....
. However, there are significant differences between those two taxa
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
as well, which includes characters that Lasiognathus shares with the oneirodids
Oneirodidae
The dreamers are a family, Oneirodidae, of deep-sea anglerfishes in the order Lophiiformes. They are the largest and most diverse group of deep-sea anglerfish, and also the least well-known with several genera represented by only one, two, or three female specimens. They are found in deep,...
not found in Thaumatichthys. Bertelsen and Struhsaker (1977) noted that, given the undefined cladistics
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
of the Oneirodidae, it was somewhat subjective
Subjectivity
Subjectivity refers to the subject and his or her perspective, feelings, beliefs, and desires. In philosophy, the term is usually contrasted with objectivity.-Qualia:...
whether Lasiognathus and Thaumatichthys were placed in their own family, in separate families, or in the Oneirodidae. comes from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
, meaning "hairy", and , meaning "jaw".
Distribution and habitat
Lasiognathus species have been collected from widely scattered localities in the AtlanticAtlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
and Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
s. L. beebei is known from the north Atlantic and off Oahu
Oahu
Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...
in Hawaiian Islands
Hawaiian Islands
The Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...
. L. waltoni is known from the central Pacific, just north of Oahu. L. intermedius is known from the western north Atlantic, the eastern south Pacific, and from off Cape Town, South Africa
Cape Town
Cape Town is the second-most populous city in South Africa, and the provincial capital and primate city of the Western Cape. As the seat of the National Parliament, it is also the legislative capital of the country. It forms part of the City of Cape Town metropolitan municipality...
. L. saccostoma is known from the north Atlantic and off the Hawaiian Islands. L. amphirhamphus is known from off the Madeira Islands
Madeira
Madeira is a Portuguese archipelago that lies between and , just under 400 km north of Tenerife, Canary Islands, in the north Atlantic Ocean and an outermost region of the European Union...
in the eastern north Atlantic. Lasiognathus specimens of uncertain species are also known from the north Pacific and the South China Sea
South China Sea
The South China Sea is a marginal sea that is part of the Pacific Ocean, encompassing an area from the Singapore and Malacca Straits to the Strait of Taiwan of around...
. They are pelagic
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
in nature, occurring to a depth of 4,000 m.
Description
Only metamorphosedMetamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
female Lasiognathus have been collected; there is presumably extreme sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in size and shape as with other deep-sea anglerfishes. These fishes have a slender body
Body
With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...
with a large, slender head
Head
In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....
measuring over 60% of the standard length
Fish measurement
Fish measurement refers to the measuring of the length of individual fish and of various parts of their anatomy. These data are used in many areas of ichthyology, including taxonomy and fisheries biology.-Overall length:...
. The mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
is huge, with the premaxillaries
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
of the upper jaw
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
enlarged and extending well beyond the short lower jaw
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
. The premaxillaries are separated anteriorly and connected by a broad elastic
Elasticity (physics)
In physics, elasticity is the physical property of a material that returns to its original shape after the stress that made it deform or distort is removed. The relative amount of deformation is called the strain....
membrane
Biological membrane
A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...
, and are hinged with the upper jaw so that they are able to flip up and down. When in the latter position, the premaxillaries completely enclose the lower jaw. There are numerous long, hooked teeth placed in roughly oblique rows on the premaxillaries.
The pterygiophore (the basal bone supporting the illicium) of Lasiognathus is unusually long amongst anglerfish, measuring some 85% of the standard length. This bone inserts dorsally on the head and is capable of sliding forwards and backwards within a trough that extends the full length of the cranium and between the epaxial musculature on the front half of the body. The illicium is also long, with a terminal esca and 2-3 bony hook-shaped denticles mounted on an appendage at the tip. The escal bulb is equipped with a flap of skin that allows adjustment of the emitted light. The sphenotic spines (above the eyes) are well-developed, as are the two articular spines (at the rear end of the lower jaw). The operculum
Operculum (fish)
The 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....
is divided into two parts, with the dorsal part split into two (rarely three) branches.
The pectoral fin lobe is small, short, and broad; the fin ray
Fish anatomy
Fish anatomy is primarily governed by the physical characteristics of water, which is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does.- Body :...
s number 5 in the dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
, 5 in the anal fin, 14-20 in the pectoral fins, and 9 in the caudal fin. The skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
is entirely naked, without spines or denticles. The coloration is a deep chocolate brown. All Lasiognathus are small fishes; L. amphirhamphus is the largest known species at 15.7 cm standard length
Fish measurement
Fish measurement refers to the measuring of the length of individual fish and of various parts of their anatomy. These data are used in many areas of ichthyology, including taxonomy and fisheries biology.-Overall length:...
. L. beebei attains a maximum length of 11.5 cm, L. intermedius 12.9 cm, L. saccostoma 7.7 cm, and L. waltoni 9.4 cm.
Biology and ecology
Little is known of the life habits of Lasiognathus. William BeebeWilliam Beebe
William Beebe, born Charles William Beebe was an American naturalist, ornithologist, marine biologist, entomologist, explorer, and author...
speculated in 1930 that the fishing apparatus of Lasiognathus might "be cast swiftly ahead, when then the hooks and the lights would so frighten any pursued fish that they would hesitate long enough to be engulfed in the onrushing maw," though Richard Ellis
Richard Ellis (biologist)
Richard Ellis is an American marine biologist, author, and illustrator. He is a research associate in the American Museum of Natural History's division of paleontology, special adviser to the American Cetacean Society, and a member of the Explorers Club. He was U.S...
considered this scenario unlikely. Nolan and Rosenblatt (1975) echoed Beebe's skepticism that the hooks were actually used to hook prey, though they proposed that "squid
Squid
Squid are 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 arranged in pairs and two, usually longer, tentacles...
tentacle
Tentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...
s could conceivably be impaled on the hooks and the prey thus secured". It has also been proposed that Lasiognathus might form its mouth into a sort of sieve
Sieve
A sieve, or sifter, separates wanted elements from unwanted material using a woven screen such as a mesh or net. However, in cooking, especially with flour, a sifter is used to aerate the substance, among other things. A strainer is a type of sieve typically used to separate a solid from a liquid...
for filter feeding. More likely, prey is simply attracted by the glowing esca to within range of the jaws.
Stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
contents reveal that Lasiognathus feeds primarily on bony fishes, such as lanternfish
Lanternfish
Cooper Lanternfishes are small mesopelagic 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...
es and bristlemouths, and occasionally takes invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s including copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some 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, amphipods, mysid shrimps, siphonophores, salp
Salp
A salp or salpa is a barrel-shaped, planktonic tunicate. It moves by contracting, thus pumping water through its gelatinous body...
s, pteropods, and chaetognaths. It is not known whether the males are parasitic; neither males nor larvae have yet been collected.
Species
The five known species of Lasiognathus can only be distinguished by the morphologyMorphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
of the esca:
- Lasiognathus amphirhamphus This species is characterized by having only two (as opposed to three) bony hooks on its esca, which are lightly pigmented. The distal escal appendage is elongated and cylindrical with a long, compressed prolongation at the tip as in L. saccostoma. The prolongation has six tiny filaments at the tip and no lateral serrations. The posterior escal appendage is broad and laterally compressed. Its species name is from the GreekGreek languageGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
for "double hook", referring to its escal hooks.
- Lasiognathus beebei This species is distinguishable by its hooks being placed on a short, transverse, fan-shaped distal escal appendage as opposed to the elongated, cylindrical appendage of all other species. Its species name honors naturalistNaturalistNaturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
William BeebeWilliam BeebeWilliam Beebe, born Charles William Beebe was an American naturalist, ornithologist, marine biologist, entomologist, explorer, and author...
.
- Lasiognathus intermedius This species has an elongated, cylindrical distal appendage with a short, cylindrical prolongation at the tip without any lateral serrations or filaments. The posterior escal appendage is cylindrical in shape. Its species name refers to its esca being intermediate in shape between those of L. beebei and those of L. saccostoma and L. waltoni.
- Lasiognathus saccostoma (syn.Synonym (taxonomy)In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
Lasiognathus ancistrophorus Maul, 1962) This species has a slender, compressed prolongation at the tip of its elongated, cylindrical distal escal appendage, with numerous lateral serrations and distal filaments. Unlike in L. amphirhamphus, there are three escal hooks and they are darkly pigmented. The posterior escal appendage is broad and laterally compressed, and relatively larger than in L. amphirhamphus.
- Lasiognathus waltoni This species is characterized by a membranous anterior crest on its escal bulb, and an elongated, cylindrical distal escal appendage without a prolongation at the tip. Its species name honors Sir Isaac Walton, author of The Compleat Angler.