Thaumatichthys
Encyclopedia
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 contrast to other anglerfishes, the bioluminescent lure (called the "esca") of Thaumatichthys is located inside its cavernous mouth
. They are worldwide in distribution and are ambush predators living near the ocean floor.
expedition in Indonesia
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
. 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
, which also possesses enlarged, hinged premaxillaries, denticles on the esca, and a branched upper operculum
. There are also significant differences between the two genera though, and Lasiognathus shares many more traits with the Oneirodidae
(in which it was formerly placed) than does Thaumatichthys.
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
off Sulawesi
. T. axeli occurs in the eastern Pacific Ocean
, while T. binghami is found in and around the Caribbean Sea
. Larva
e that could not be referred to species have also been found off the Gulf of Guinea
in the southern Atlantic Ocean
and in the southern Mozambique Channel
in the eastern Indian Ocean
.
Uniquely amongst deep-sea anglerfish, adult Thaumatichthys are benthic in nature; T. binghami and T. pagidostomus are found on the continental shelf
between 1,000–2,000 m, while T. axeli is found in the abyssal zone
at about 3,600 m.
As with most other deep-sea anglerfishes, Thaumatichthys shows extreme sexual dimorphism
with the female
s much larger and different in morphology
from the male
s. Female Thaumatichthys are characterized by a long, broad, flattened head
with enlarged premaxillaries on the upper jaw that overhang the relatively short lower jaw. The premaxillaries are hinged with the skull
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; 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
fold connecting the anterior 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 denticle. The size of the transparent window in the bulb can be adjusted to change the amount of light emanating from the lure.
The eye
s are tiny and placed close to the corners of the mouth. There are numerous black papilla
e with white tips, resembling those of the lateral line
(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
. The fin rays number 4 in the anal fin, 7 in the caudal fin, 6–7 in the dorsal fin
, and 14–16 in the pectoral fins. The upper part of the operculum
is divided into 5–13 radiating branches. The skin
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 organ
s, 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.
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 cucumbers as well as plant
matter, suggesting that these fishes are omnivore
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
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
, they descend deeper until they reach the bottom. The larvae can be identified by their divided operculum and a subdermal pigment
layer that covers the entire head and body.
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 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 three known 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...
. Its scientific name means "wonder-fish" in Greek
Greek language
Greek 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;...
; 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 lure (called the "esca") of Thaumatichthys is located inside its cavernous 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....
. They are worldwide in distribution and are ambush predators living near the ocean floor.
Taxonomy
The first specimen of Thaumatichthys was collected by an AmericanUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
expedition in Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
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
Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, the characteristic arrangement, kind, and number of teeth in a given species at a given age...
. 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
Lasiognathus
Lasiognathus is a genus of deep-sea anglerfish in the family Thaumatichthyidae, with five species known from the Atlantic and Pacific Oceans...
, which also possesses enlarged, hinged premaxillaries, denticles on the esca, 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....
. There are also significant differences between the two genera though, and Lasiognathus shares many more traits with the Oneirodidae
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,...
(in which it was formerly placed) than does Thaumatichthys.
Distribution and habitat
Thaumatichthys is known from tropical oceanOcean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
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
Gulf of Tomini
The Gulf of Tomini is a gulf near the island of Sulawesi, Indonesia.It is bounded on its north and west sides by the Minahassa Peninsula and on the south side by the East Peninsula, Sulawesi....
off Sulawesi
Sulawesi
Sulawesi is one of the four larger Sunda Islands of Indonesia and is situated between Borneo and the Maluku Islands. In Indonesia, only Sumatra, Borneo, and Papua are larger in territory, and only Java and Sumatra have larger Indonesian populations.- Etymology :The Portuguese were the first to...
. T. axeli occurs in the eastern 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...
, while T. binghami is found in and around the Caribbean Sea
Caribbean Sea
The Caribbean Sea is a sea of the Atlantic Ocean located in the tropics of the Western hemisphere. It is bounded by Mexico and Central America to the west and southwest, to the north by the Greater Antilles, and to the east by the Lesser Antilles....
. Larva
Larva
A larva 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...
e that could not be referred to species have also been found off the Gulf of Guinea
Gulf of Guinea
The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean between Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian is in the gulf....
in the southern Atlantic Ocean
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 in the southern Mozambique Channel
Mozambique Channel
The Mozambique Channel is a portion of the Indian Ocean located between the island nation of Madagascar and southeast Africa, primarily the country of Mozambique. It was a World War II clashpoint during the Battle of Madagascar...
in the eastern Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
.
Uniquely amongst deep-sea anglerfish, adult Thaumatichthys are benthic in nature; T. binghami and T. pagidostomus are found on the continental shelf
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
between 1,000–2,000 m, while T. axeli is found in the abyssal zone
Abyssal zone
The abyssal zone is the abyssopelagic layer or pelagic zone that contains the very deep benthic communities near the bottom of oceans. "Abyss" derives from the Greek word ἄβυσσος, meaning bottomless. At depths of 4,000 to 6,000 metres , this zone remains in perpetual darkness and never receives...
at about 3,600 m.
Description
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:...
with the female
Female
Female is the sex of an organism, or a part of an organism, which produces non-mobile ova .- Defining characteristics :The ova are defined as the larger gametes in a heterogamous reproduction system, while the smaller, usually motile gamete, the spermatozoon, is produced by the male...
s much larger and different in morphology
Morphology (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....
from the male
Male
Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
s. Female Thaumatichthys are characterized by a long, broad, flattened 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....
with enlarged premaxillaries on the upper jaw that overhang the relatively short lower jaw. The premaxillaries are hinged with the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
in such a way that they can be moved down to enclose the lower jaw in a manner similar that of a Venus flytrap
Venus Flytrap
The Venus Flytrap , Dionaea muscipula, is a carnivorous plant that catches and digests animal prey—mostly insects and arachnids. Its trapping structure is formed by the terminal portion of each of the plant's leaves and is triggered by tiny hairs on their inner surfaces...
. The outer margin of the premaxillaries bear six rows of long, conical, recurved teeth; 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
-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...
fold connecting the anterior 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 denticle. The size of the transparent window in the bulb can be adjusted to change the amount of light emanating from the lure.
The eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s are tiny and placed close to the corners of the mouth. There are numerous black papilla
Papilla (fish mouth structure)
The papilla, in certain kinds of fish, particularly rays, sharks, and catfish, are small lumps of dermal tissue found in the mouth, where they are "distributed uniformly on the tongue, palate, and pharynx"...
e with white tips, resembling those of the lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , 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...
(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
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...
. The fin rays number 4 in the anal fin, 7 in the caudal fin, 6–7 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...
, and 14–16 in the pectoral fins. The upper part of 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 5–13 radiating branches. 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 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 organ
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
s, 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-trapMousetrap
A mousetrap is a specialized type of animal trap designed primarily to catch mice; however, it may also trap other small animals. Mousetraps are usually set in an indoor location where there is a suspected infestation of rodents. There are various types of mousetrap, each with its own advantages...
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
Respiration (physiology)
'In physiology, respiration is defined as the transport of oxygen from the outside air to the cells within tissues, and the transport of carbon dioxide in the opposite direction...
. Despite this highly specialized predatory apparatus however, examination of 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 revealed sea cucumbers as well as plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
matter, suggesting that these fishes are omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
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
Larva
A larva 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...
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
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...
, they descend deeper until they reach the bottom. The larvae can be identified by their divided operculum and a subdermal pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
layer that covers the entire head and body.
Species
- Thaumatichthys axeliThaumatichthys axeliThaumatichthys axeli is a bottom-dwelling deep-sea anglerfish of the family Thaumatichthys. Thaumatichthys axeli lives at a depth of around 3,600 meters , deeper than any other member of the family Thaumatichthys. As with other members of the family, they possess a distinctive forked light organ...
(Bruun, 1953) Both this species and T. binghami have relatively shorter premaxillaries, at 23.5–27% of standard length. 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 wartWartA wart is generally a small, rough growth, typically on a human’s hands or feet but often other locations, that can resemble a cauliflower or a solid blister. They are caused by a viral infection, specifically by human papillomavirus 2 and 7. There are as many as 10 varieties of warts, the most...
-like and not tapering. - Thaumatichthys binghami Parr, 1927 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 fingerFingerA finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....
-like and tapering. - Thaumatichthys pagidostomus Smith and Radcliffe, 1912 This species has relatively longer premaxillaries than the other species (measuring 33% of standard length), and the anterior premaxillary teeth are long.