| Heterotardigrada | |
|---|---|
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| Echiniscus succineus under PCM (left) and SEM (right) | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Tardigrada |
| Class: | Heterotardigrada Marcus, 1927 |
| Families | |
Order Arthrotardigrada Contents | |
Heterotardigrades (Heterotardigrada) is a class that includes tardigrades (water bears) that have cephalic appendages and legs with four separate but similar digits or claws on each. 444 species have been described. [1]
The anatomy of the reproductive system is an important defining feature in distinguishing the different groups of tardigrades. Heterotardigrades have gonoducts that open to the outside through a preanal gonopore, rather than opening into the rectum as in the only other confirmed class of tardigrades, the Eutardigrada. The third class, Mesotardigrada, is represented by a single species known from a single specimen that is now lost, and the location from which that specimen was collected has since been destroyed by an earthquake, so its reproductive anatomy has not been studied recently.
Some orders of heterotardigrades are marine, others are terrestrial, but as for all tardigrades, all are aquatic in the sense that they must be surrounded by at least a film of moisture in order to be active – though they can survive in a dormant state if the habitat dries out.
The gastrotrichs, commonly referred to as hairybellies or hairybacks, are a group of microscopic (0.06–3.0 mm), cylindrical, acoelomate animals, and are widely distributed and abundant in freshwater and marine environments. They are mostly benthic and live within the periphyton, the layer of tiny organisms and detritus that is found on the seabed and the beds of other water bodies. The majority live on and between particles of sediment or on other submerged surfaces, but a few species are terrestrial and live on land in the film of water surrounding grains of soil. Gastrotrichs are divided into two orders, the Macrodasyida which are marine, and the Chaetonotida, some of which are marine and some freshwater. Nearly 800 species of gastrotrich have been described.
Gnathostomulids, or jaw worms, are a small phylum of nearly microscopic marine animals. They inhabit sand and mud beneath shallow coastal waters and can survive in relatively anoxic environments. They were first recognised and described in 1956.
Mesotardigrada is one of three classes of tardigrades, consisting of a single species, Thermozodium esakii. The animal reportedly has six claws of equal length at each foot. This species was described in 1937 by German zoologist Gilbert Rahm from a hot spring near Nagasaki, Japan. The inability of taxonomists to replicate Rahm's finding has cast doubt on the accuracy of the description, making T. esakii, and by extension the entire class Mesotardigrada, a taxon inquirendum.
Eutardigrada are a class of tardigrades (Tardigrada) without lateral appendages. Primarily freshwater bound, some species have secondarily gained the ability to live in marine environments (Halobiotus). By cryptobiosis many species are able to live temporarily in very dry environments. More than 700 species have been described.
The Caudata are a group of amphibians containing the extant salamanders and all extinct species of amphibians more closely related to salamanders than to frogs. They are typically characterized by a superficially lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults.
Pauropoda is a class of small, pale, millipede-like arthropods in the subphylum Myriapoda. More than 900 species in twelve families are found worldwide, living in soil and leaf mold. Pauropods look like centipedes or millipedes and may be a sister group of the latter, but a close relationship with Symphyla has also been posited. The name Pauropoda derives from the Greek pauros and pous or podus, because most species in this class have only nine pairs of legs as adults, a smaller number than those found among adults in any other class of myriapods.
The Alytidae are a family of primitive frogs. Their common name is painted frogs or midwife toads. Most are endemic to Europe, but three species occur in northwest Africa, and a species formerly thought to be extinct is found in Israel.
Parasitiformes are a superorder of Arachnids, constituting one of the two major groups of mites, alongside Acariformes. Parasitiformes has, at times, been classified at the rank of order or suborder.
Tardigrades, known colloquially as water bears or moss piglets, are a phylum of eight-legged segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them Kleiner Wasserbär. In 1777, the Italian biologist Lazzaro Spallanzani named them Tardigrada, which means "slow steppers".
Pristimantis is a very large genus of frogs distributed in the southern Caribbean islands and in Central and South America from Honduras to northern Argentina and southern Brazil. With 596 described species, the genus had more species than any other genus of vertebrate animals. Many of these species genus are endemic to the Northwestern Andean montane forests ecoregion in north-western South America.
Echiniscus testudo is a cosmopolitan species of tardigrade.
Craugastoridae, commonly known as fleshbelly frogs, is a family of New World direct-developing frogs. As delineated here, following the Amphibian Species of the World, it contains 129 species. They are found from the southern United States southwards to Central and South America.
Acutuncus is a genus of tardigrades containing a single species, Acutuncus antarcticus. Tardigrades, which are eight-legged micro-animals, are commonly referred to as water bears or moss piglets and are found all over the world in varying extreme habitats. First discovered in 1904 and originally named Hypsibius antarcticus, Acutuncus antarcticus is the most abundant tardigrade species in Antarctica.
Polyxenida is an order of millipedes readily distinguished by a unique body plan consisting of a soft, non-calcified body ornamented with tufts of bristles – traits that have inspired the common names "bristly millipedes" or "pincushion millipedes". There are at least 86 species in four families worldwide, and are the only living members of the subclass Penicillata.
Glomeridesmida is an order of millipedes in the infraclass Pentazonia containing 2 families and at least 31 species. Glomeridesmida is the only living order of the superorder Limacomorpha. Also known as slug millipedes, glomeridesmidans are small and somewhat flattened, and unlike other orders of Pentazonia, are unable to roll into a ball. Ocelli (eyes) are absent.
Platydesmida is an order of millipedes containing two families and over 60 species. Some species practice paternal care, in which males guard the eggs.
Beorn leggi is an extinct species of tardigrade and the first known fossil tardigrade, discovered c. 1940 and described in 1964 from Late Cretaceous amber from Manitoba, Canada. It is the only species in the genus Beorn, and family Beornidae. It is one of two fossil tardigrades known from the Cretaceous, the other being Milnesium swolenskyi from the Turonian New Jersey amber.
Arthrotardigrada are an order of tardigrades, first described by Marcus in 1927.
Echiniscus madonnae is a tardigrade species, genus of Echiniscus. It was described by Polish zoologists Michalczyk and Kaczmarek Łukasz in South America in 2006, and named in honor of American singer-songwriter Madonna.
Milnesium alpigenum is a species of tardigrade that falls under the Tardigrada phylum. Like its taxonomic relatives it is an omnivorous predator that feeds on other small organisms, such as algae, rotifers, and nematodes. M. alpigenum was discovered by Christian Gottfried Ehrenberg in 1853. It is very closely related to Milnesium tardigradum along with many other species from the Milnesium genus.
| Authority control databases: National |
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