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Encyclopedia > Rotifer
Wikipedia:How to read a taxobox
How to read a taxobox
Rotifers
Philodina, feeding
Philodina, feeding
Scientific classification
Kingdom: Animalia
Subkingdom: Eumetazoa
Superphylum: Platyzoa
Phylum: Rotifera
Cuvier, 1798
Classes

Monogononta
Digononta A rotifer taken from standing water. ... Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. ... “Animalia” redirects here. ... subgroups Ctenophora Cnidaria Bilateria Eumetazoa is a clade comprising all major animal groups except sponges. ... The Platyzoa are a group of protostome animals. ... Georges Cuvier Baron Georges Léopold Chrétien Frédéric Dagobert Cuvier (August 23, 1769–May 13, 1832) was a French naturalist and zoologist. ... The monogononts (Monogononta) are a class of rotifers, found mostly in freshwater but also in soil and marine environments. ... Orders Bdelloidea Seisonidae The digononts (Digononta) are a class of rotifers. ...

The rotifers make up a phylum of microscopic and near-microscopic pseudocoelomate animals. They were first described by John Harris in 1696 (Hudson and Gosse, 1886). Leeuwenhoek is mistakenly given credit for being the first to describe rotifers but Harris had produced sketches in 1703. Most rotifers are around 0.1-0.5 mm long, and are common in freshwater throughout the world with a few saltwater species. Rotifers may be free swimming and truly planktonic, others move by inchworming along the substrate whilst some are sessile, living inside tubes or gelatinous holdfasts. About 25 species are colonial (i.e. Sinantherina semibullata), either sessile or planktonic. By the broadest definition, a body cavity is any fluid filled space in a multicellular organism. ... “Animalia” redirects here. ... Anton van Leeuwenhoek Anton van Leeuwenhoek (October 24, 1632 - August 30, 1723, full name Thonius Philips van Leeuwenhoek (pronounced Layewenhook) was a Dutch tradesman and scientist from Delft, Netherlands. ... Photomontage of plankton organisms Plankton are any drifting organism that inhabits the water column of oceans, seas, and bodies of fresh water. ...

Contents

Structure and form

Rotifers get their name (derived from Latin and meaning "wheel-bearer"; they have also been called wheel animalcules) from the corona, which is composed of several ciliated tufts around the mouth that in motion resemble a wheel. These create a current that sweeps food into the mouth, where it is chewed up by a characteristic pharynx (mastax) containing tiny jaws. It also pulls the animal, when unattached, through the water. Most free-living forms have pairs of posterior toes to anchor themselves while feeding. Rotifers have Bilateral symmetry Rotifers have a variety of different shapes. There is a well-developed cuticle which may be thick and rigid, giving the animal a box-like shape, or flexible, giving the animal a worm-like shape; such rotifers are respectively called loricate and illoricate. Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... Animalcule is an older term for a microscopic animal or protozoan. ... A corona is a type of plasma atmosphere of the Sun or other celestial body, extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. ... cross-section of two cilia, showing 9+2 structure A cilium (plural cilia) is a fine projection from a eukaryotic cell that constantly beats in one direction. ... The pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea. ... In biology, bilateral symmetry is a characteristic of multicellular organisms, particularly animals. ... It has been suggested that this article or section be merged into Eponychium. ...


Like many other microscopic animals, adult rotifers frequently exhibit eutely - they have a fixed number of cells within a species, usually on the order of one thousand.


Reproduction

Rotifers have the ability to alternate reproduction by sexual or asexual means, depending on their class and the varied conditions of their environment. In the Class Monogononta, rotifers reproduce by alternating means, though most times asexually.


Males in the Class Monogononta may be either present or absent depending on the species and environmental conditions. In the absence of males, reproduction is by parthenogenesis and results in clonal offspring that are genetically identical to the parent. Individuals of some species form two distinct types of parthenogenetic eggs; one type develops into a normal parthenogenetic female, while the other occurs in response to a changed environment and develops into a degenerate male that lacks a digestive system, but does have a complete male reproductive system that is used to inseminate females thereby producing fertilized 'resting eggs'. Resting eggs develop into zygotes that are able to survive extreme environmental conditions such as may occur during winter or when the pond dries up. These eggs resume development and produce a new female generation when conditions improve again. The life span of monogonont females varies from a couple of days to about three weeks. It has been suggested that this article or section be merged into Asexual reproduction. ... It has been suggested that Biparental zygote be merged into this article or section. ...


Bdelloid rotifers are unable to produce resting eggs, but many can survive prolonged periods of adverse conditions after desiccation. This facility is termed anhydrobiosis, and organisms with these capabilities are termed anhydrobionts. Under drought conditions, bdelloid rotifers contract into an inert form and lose almost all body water; when rehydrated, however, they resume activity within a few hours. Bdelloids can survive the dry state for prolonged periods, with the longest well-documented dormancy being nine years. While in other anhydrobionts, such as the brine shrimp, this desiccation tolerance is thought to be linked to the production of trehalose, a non-reducing disaccharide (sugar), bdelloids apparently lack the ability to synthesise trehalose. Desiccation is the state of extreme dryness, or the process of extreme drying. ... Cryptobiosis is an ametabolic state of life entered by some lower organisms in response to adverse environmental conditions such as desiccation, freezing, and oxygen deficiency. ... It has been suggested that Sea-Monkey be merged into this article or section. ... Trehalose also known as mycose is a 1-alpha (disaccharide) sugar found extensively but not abundantly in nature. ... Magnification of grains of sugar, showing their monoclinic hemihedral crystalline structure. ...


Bdelloid rotifer genomes contain two or more divergent copies of each gene, suggesting a long term asexual evolutionary history (Welch etal 2004). Four copies of hsp82 are, for example, found. Each is different and found on a different chromosome excluding the possibility of homozygous sexual reproduction.


Taxonomy

There are about 2000 species, divided into two classes. The parasitic Acanthocephala may belong among the rotifers as well. These phyla belong in a group called the Platyzoa. In biology, a species is one of the basic units of biodiversity. ... Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... Classes Archiacanthocephala Palaeacanthocephala Eoacanthocephala The Acanthocephala (gr. ... The Platyzoa are a group of protostome animals. ...


References

J.L.M. Welch, D.B.M Welch, and M. Meselson. Cytogenic evidence for asexual evolution of bdelloid rotifers. Proc. Nat. Acad. Sci., Feb. 2004 vol. 101, no. 6, pp.1618-1621


External links

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  Results from FactBites:
 
References - Production and Application of Rotifers in Aquaculture Page 2 (1224 words)
The second indicator for assessing the status of rotifer mass cultures is egg ratio, which is the number of eggs carried by females divided by the number of females.
Rotifer bisexual reproduction is affected by both internal and external factors (Hagiwara et al., 1991).
The ability of rotifers to undergo mictic multiplication and to generate the resting eggs is thought to develop in an evolutionary process to cope with severe environmental changes (Fukusho, 1989).
  More results at FactBites »

 
 

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