The Wonderfish (''Thaumatichthys'') 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 three known

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 ...

. Its

scientific name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

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 contrast to other anglerfishes, 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 ...

lure (called the "esca") of ''Thaumatichthys'' is located inside its cavernous

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 ...

. They are worldwide in distribution and are ambush

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

s living near the ocean floor.

Taxonomy

The first specimen of ''Thaumatichthys'' was collected by an

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

expedition in

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

in 1908 and given the species name ''pagidostomus'' ("trap-mouthed"). A subsequent specimen from the north Atlantic was placed by Regan and Trewavas (1932) into a new genus, ''Amacrodon'', based on differences in

dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolo ...

. Bruun assigned a specimen collected by the Galathea Expedition of 1950–52 to a third genus, ''Galatheathauma'' ("Galathea's wonder"), as it was much larger than the previous specimens. However, a later examination of the then-32 known specimens showed that these differences were attributable to age, and thus there was only one valid genus, ''Thaumatichthys'', with three species. The closest relative of ''Thaumatichthys'' is ''

Lasiognathus The complete anglerfish (''Lasiognathus'') is a genus of deep-sea anglerfish in the family Thaumatichthyidae, with six species known from the Atlantic and Pacific Oceans. Its lure apparatus appears to consist of a fishing rod (the projecting bas ...

'', which also possesses enlarged, hinged premaxillaries,

denticle A denticle is any small tooth-like or bristle-like structure. "Denticle" may refer to: * Denticle (tooth feature), serrations on the teeth of dinosaurs, lizards, sharks, and mammals * Dermal denticles or placoid scales, in cartilaginous fishes * ...

s on the

esca 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 co ...

, and a branched upper operculum. There are also significant differences between the two genera though, and ''Lasiognathus'' shares many more traits with the family Oneirodidae (in which it was formerly placed) than does ''Thaumatichthys''.Pietsch, T.W. (2005)
Thaumatichthyidae. Wolftrap Seadevils.
''The Tree of Life Web Project.'' Retrieved on December 7, 2008.

Species

There are currently three recognized species in this genus: * '' Thaumatichthys axeli''

Bruun Bruun is a surname of North Germanic origin. The meaning is ''brown'' (''brun'' in Danish, Swedish and Norwegian). In Denmark, the name is known to have been in use since the 13th century in the form Bruun. Other spelling variants are ''Bruhn'' and ...

, 1953 * '' Thaumatichthys binghami'' A. E. Parr, 1927 * '' Thaumatichthys pagidostomus'' H. M. Smith &

Radcliffe Radcliffe or Radcliff may refer to: Places * Radcliffe Line, a border between India and Pakistan United Kingdom * Radcliffe, Greater Manchester ** Radcliffe Tower, the remains of a medieval manor house in the town ** Radcliffe tram stop * ...

, 1912

Distribution and habitat

''Thaumatichthys'' is known from

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...

ic waters worldwide. ''T. pagidostoma'', the first species to be discovered, is only known from a single specimen caught at a depth of 1,440 m in the

Gulf of Tomini The Gulf of Tomini ( id, Teluk Tomini), also known as the Bay of Tomini, is the equatorial gulf which separates the Minahassa Peninsula, Minahassa (Northern) and East Peninsula, Sulawesi, East Peninsulas of the island of Sulawesi (Celebes) in In ...

off

Sulawesi Sulawesi (), also known as Celebes (), is an island in Indonesia. One of the four Greater Sunda Islands, and the world's eleventh-largest island, it is situated east of Borneo, west of the Maluku Islands, and south of Mindanao and the Sulu Ar ...

. ''T. axeli'' occurs in the eastern

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 ...

, while ''T. binghami'' is found in and around the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

Larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e that could not be referred to species have also been found off the

Gulf of Guinea The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean from Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian (zero degrees latitude and longitude) is in the ...

in the southern

Atlantic Ocean 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 ...

and in the southern

Mozambique Channel The Mozambique Channel (french: Canal du Mozambique, mg, Lakandranon'i Mozambika, pt, Canal de Moçambique) is an arm of the Indian Ocean located between the Southeast African countries of Madagascar and Mozambique. The channel is about long ...

in the eastern

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

. Uniquely amongst deep-sea anglerfish, adult ''Thaumatichthys'' are

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

in nature; ''T. binghami'' and ''T. pagidostomus'' are found on the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

between 1,000–2,000 m, while ''T. axeli'' is found in the

abyssal zone The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. "Abyss" derives from the Greek word , meaning bottomless. At depths of , this zone remains in perpetual darkness. It covers 83% of the total area of the ocean a ...

at about 3,600 m.

Description

As with most other deep-sea anglerfishes, ''Thaumatichthys'' shows 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 ...

with the

female Female (Venus symbol, symbol: ♀) is the sex of an organism that produces the large non-motile ovum, ova (egg cells), the type of gamete (sex cell) that fuses with the Sperm, male gamete during sexual reproduction. A female has larger gamet ...

s much larger and different in

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, ...

from the

male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to ...

s. Female ''Thaumatichthys'' are characterized by a long, broad, flattened

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 ...

with enlarged premaxillaries on the upper jaw that overhang the relatively short lower jaw. The premaxillaries are hinged with the

skull 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 ...

in such a way that they can be moved down to enclose the lower jaw in a manner similar that of a Venus flytrap. The outer margin of the premaxillaries bear six rows of long, conical, recurved

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 ...

; the teeth in the lower jaw are much shorter. The number and length of the teeth increases as the fish grows. The distinctive lure of ''Thaumatichthys'' is achieved by an "upside-down" orientation of the illicium (the "fishing rod"): its base is embedded in 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 ...

fold connecting the

anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

ends of the premaxillaries, and the short illicium projects down and back so that the esca at the tip hangs down from the roof of the mouth. The escal bulb terminates in a pair of forked tendrils and bears varying numbers of lateral lobes and a single curved

. The size of the transparent window in the bulb can be adjusted to change the amount of light emanating from the lure. The

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

s are tiny and placed close to the corners of the mouth. There are numerous black

papilla Papilla (Latin, 'nipple') or papillae may refer to: In animals * Papilla (fish anatomy), in the mouth of fish * Basilar papilla, a sensory organ of lizards, amphibians and fish * Dental papilla, in a developing tooth * Dermal papillae, part of ...

e with white tips, resembling those of the

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

(and likely belonging to the same sensory system), inside the mouth. The body is fairly slender and depressed for a deep-sea anglerfish, with a relatively well developed

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 ...

. The fin rays number 4 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 ...

, 7 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 ...

, 6–7 in the

, and 14–16 in 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 ...

s. The upper part of the operculum is divided into 5–13 radiating branches. The

is velvet black or dark brown, with numerous small spines on the lower part of the head and body. The one specimen of ''T. pagidostomus'' measured 6 cm long, the largest known specimen of ''T. binghami'' measured 29 cm long, and the largest specimen of ''T. axeli'' measured 36.5 cm long. The males are small and slender, with greatly enlarged olfactory organs, long hooked denticles at the tips of the jaws, and no esca. The skin is a uniform dark brown with small spines throughout. As the male matures, the body and head become less deep and the jaws become more prolongated. The largest known male specimen measured 45 mm long.

Biology and ecology

The unusual jaw mechanism and esca of ''Thaumatichthys'' has been described as a "living mouse-trap with bait". The premaxillaries on either side of the upper jaw are able to rotate nearly 180° down to trap prey attracted by the luminescent lure; this closing action is effected by large, extremely well developed upper jaw muscles. Muscles in the illicium allow the esca to be swung forward and backward, so as to better entice prey inside the mouth. The upper jaw mechanism enables prey to be captured without the lower jaw, which can remain moving for the purposes of respiration. Despite this highly specialized predatory apparatus however, examination of stomach contents revealed

sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothuria ...

s as well as

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

matter, suggesting that these fishes are

omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...

s that will swallow anything edible. It is unknown whether male ''Thaumatichthys'' are parasitic. The structure of the jaws in mature males suggests that feeding is impaired after metamorphosis. The

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e are epipelagic like those of other deep-sea anglerfishes, and are found at depths of no more than 100 m. As the larvae grow and approach

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

, they descend deeper until they reach the bottom. The larvae can be identified by their divided operculum and a

subdermal The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The types of cells found in the layer are fibroblasts, adipose cells, and macro ...

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compo ...

layer that covers the entire head and body. The species differ as follows: *'' Thaumatichthys axeli'' Both this species and ''T. binghami'' have relatively shorter premaxillaries, at 23.5–27% of

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 esca of this species has a single pair of lateral lobes that are enlarged into tapering filaments in the largest individuals, and the uppermost median appendage on its esca is wart-like and not tapering. *'' Thaumatichthys binghami'' This species is similar to ''T. axeli'', except that its esca bears 2–3 pairs of lateral lobes that are elongated into tapering filaments in the largest individuals, and the uppermost medial appendage on the esca is

finger A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers ( Pentadactyly). Chambers ...

-like and tapering. *'' Thaumatichthys pagidostomus'' This species has relatively longer premaxillaries than the other species (measuring 33% of

), and the anterior premaxillary teeth are long.

References

{{Taxonbar, from=Q2712927 Thaumatichthyidae Marine fish genera Taxa named by Hugh McCormick Smith Taxa named by Lewis Radcliffe