The complete anglerfish (''Lasiognathus'') is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of deep-sea

anglerfish The anglerfish are fish of the teleost order Lophiiformes (). They are bony fish named for their characteristic mode of predation, in which a modified luminescent fin ray (the esca or illicium) acts as a lure for other fish. The luminescence ...

in the family

Thaumatichthyidae Thaumatichthyidae, the wolftrap anglers, is a small family of deep-sea anglerfishes, containing two genera and eight species found in all oceans. They are commonly known as wolftrap anglers or wolftrap seadevils because of their distinctive upper ...

, with six

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 ...

known from the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

and

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

s. Its lure apparatus appears to consist of a

fishing rod A fishing rod is a long, thin rod used by angling, anglers to fishing, catch fish by manipulating a fishing line, line ending in a fish hook, hook (formerly known as an ''angle'', hence the term "angling"). At its most basic form, a fishing ...

(the projecting basal bone or pteropterygium), a fishing line (the illicium, a modified

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

ray Ray may refer to: Fish * Ray (fish), any cartilaginous fish of the superorder Batoidea * Ray (fish fin anatomy), a bony or horny spine on a fin Science and mathematics * Ray (geometry), half of a line proceeding from an initial point * Ray (g ...

), bait (the

bioluminescent Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some Fungus, fungi, microorganisms including ...

esca), and hooks (large

dermal denticle A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as we ...

s). It is also distinctive for an enormous upper jaw with

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

ries that can be folded down to enclose the much shorter lower jaw.

Systematics

The closest relative of ''Lasiognathus'' is '' Thaumatichthys'', which also has enlarged and hinged

ries, escal denticles, and a branched upper operculum. However, there are significant differences between those two taxa as well, which include characteristics that ''Lasiognathus'' shares with the oneirodids not found in ''Thaumatichthys''. Bertelsen and Struhsaker (1977) noted that, given the undefined

cladistics Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

of the Oneirodidae, it was somewhat subjective whether ''Lasiognathus'' and ''Thaumatichthys'' were placed in their own family, in separate families, or in the Oneirodidae.

Etymology

' comes from the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

', meaning "hairy", and ', meaning "jaw".''Lasiognathus''
''California Academy of Sciences''. (Apr 26, 2008 version cached by ''Google.com''). Retrieved on December 9, 2008.

Species

There are currently 6 recognized species in this genus: * '' Lasiognathus amphirhamphus'' Pietsch, 2005 * '' Lasiognathus beebei''

Regan The family name Regan, along with its cognates O'Regan, O Regan, Reagan, and O'Reagan, is an Anglicized form of the Irish surname Ó Riagáin or Ó Ríogáin, from Ua Riagáin. The meaning is likely to have originated in ancient Gaelic ''ri'' ...

& Trewavas, 1932 * '' Lasiognathus dinema'' Pietsch & T. T. Sutton, 2015 * '' Lasiognathus intermedius'' Bertelsen & Pietsch, 1996 * '' Lasiognathus saccostoma''

, 1925 * '' Lasiognathus waltoni'' Nolan &

Rosenblatt Rosenblatt is a surname of German and Jewish origin, meaning "rose leaf". People with this surname include: * Albert Rosenblatt (born 1936), New York Court of Appeals judge * Dana Rosenblatt, known as "Dangerous" (born 1972), American boxer * Elie ...

, 1975

Distribution and habitat

''Lasiognathus'' species have been collected from widely scattered localities in the

and

s. ''L. beebei'' is known from the north Atlantic and off

Oahu Oahu () (Hawaiian language, Hawaiian: ''Oʻahu'' ()), also known as "The Gathering place#Island of Oʻahu as The Gathering Place, Gathering Place", is the third-largest of the Hawaiian Islands. It is home to roughly one million people—over t ...

Hawaiian Islands The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost Kur ...

. ''L. waltoni'' is known from the central Pacific, just north of Oahu. ''L. dinema'' is known from the northern

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...

. ''L. intermedius'' is known from the western north Atlantic, the eastern south Pacific, and from off

Cape Town, South Africa Cape Town ( af, Kaapstad; , xh, iKapa) is one of South Africa's three capital cities, serving as the seat of the Parliament of South Africa. It is the legislature, legislative capital of the country, the oldest city in the country, and the sec ...

. ''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 The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Phil ...

. They are

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or wa ...

in nature, occurring to a depth of 4,000 m.

Description

Only metamorphosed female ''Lasiognathus'' have been collected; there is presumably extreme

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

in size and shape, as with other deep-sea anglerfishes. These fishes have a slender

body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of anima ...

with a large, slender

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may ...

measuring over 60% of the

standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

. The

mouth In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...

is huge, with the

ries of the upper jaw enlarged and extending well beyond the short lower jaw. The premaxillaries are separated anteriorly and connected by a broad

elastic Elastic is a word often used to describe or identify certain types of elastomer, elastic used in garments or stretchable fabrics. Elastic may also refer to: Alternative name * Rubber band, ring-shaped band of rubber used to hold objects togeth ...

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 A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

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 The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

and between the

epaxial In adult vertebrates, trunk muscles can be broadly divided into hypaxial muscles, which lie ventral to the horizontal septum of the vertebrae and epaxial muscles, which lie dorsal to the septum. Hypaxial muscles include some vertebral muscles, the ...

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 Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

lobe is small, short, and broad; the fin rays number 5 in the

, 5 in the

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

, 14–20 in the pectoral fins, and 9 in the

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

.Pietsch, T.W. (2005)
Thaumatichthyidae. Wolftrap Seadevils.
''The Tree of Life Web Project.'' Retrieved on December 9, 2008. The

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

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

. ''L. beebei'' attains a maximum length of 11.5 cm, ''L. dinema'' 9.5 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 Beebe 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 True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

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 fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

es, such as

lanternfish Lanternfishes (or myctophids, from the Greek μυκτήρ ''myktḗr'', "nose" and ''ophis'', "serpent") are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represente ...

es and

bristlemouth The Gonostomatidae are a family of mesopelagic marine fish, commonly named bristlemouths, lightfishes, or anglemouths. It is a relatively small family, containing only eight known genera and 32 species. However, bristlemouths make up for their l ...

s, and occasionally takes

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s including

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) ...

amphipod Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...

mysid shrimp Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in ...

s, siphonophores,

salp A salp (plural salps, also known colloquially as “sea grape”) or salpa (plural salpae or salpas) is a barrel-shaped, planktic tunicate. It moves by contracting, thereby pumping water through its gelatinous body, one of the most efficient ...

s, pteropods, and chaetognaths. It is not known whether the males are parasitic; neither males nor larvae have yet been collected. The six known species of ''Lasiognathus'' can only be distinguished by the

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

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. *''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. *''Lasiognathus dinema'' This species is similar to any of the five previously described members of the genus, these species is unique in having a cylindrical, internally pigmented, anterior escal appendage and a pair of elongate distal escal appendages. *''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'' 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.

References

{{Taxonbar, from=Q2710566 Thaumatichthyidae Taxa named by Charles Tate Regan Marine fish genera