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Syndermata
Syndermata is a clade of animals that, in some systems, is considered synonymous with Rotifera. Older systems separate Rotifera and Acanthocephala as different phyla, and group them both under Syndermata., p. 788ff. – see particularly p. 804 This clade is placed in the Platyzoa. Phylogeny Phylogenetic analysis of the 18S ribosomal gene has revealed that the Acanthocephala, formerly considered a separate phylum are most closely related to the rotifers. They are possibly closer to the two rotifer classes Bdelloidea and Monogononta than to the other class, Seisonidea, producing the names and relationships shown in the cladogram below. A study of the gene order in the mitochondria suggests that Seisonidea and Acanthocephala are sister clades and that the Bdelloidea are the sister clade to this group. This has since been corroborated by the discovery of a fossil stem-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bdelloidea
Bdelloidea (from Greek language, Greek βδέλλα, ''bdella'' 'leech') is a Class (biology), class of rotifers found in freshwater habitats all over the world. There are over 450 described species of bdelloid rotifers (or 'bdelloids'), distinguished from each other mainly on the basis of Morphology (biology), morphology. The main characteristics that distinguish bdelloids from #Evolutionary Relationships, related groups of rotifers are exclusively parthenogenesis, parthenogenetic reproduction and the ability to survive in dry, harsh environments by entering a state of desiccation-induced dormancy (anhydrobiosis) at any life stage. They are often referred to as "ancient asexuals" due to their unique asexual history that spans back to over 25 million years ago through fossil evidence. Bdelloid rotifers are microscopic organisms, typically between 150 and 700 μm in length. Most are slightly too small to be seen with the naked eye, but appear as tiny white dots through even ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Syndermata
Syndermata is a clade of animals that, in some systems, is considered synonymous with Rotifera. Older systems separate Rotifera and Acanthocephala as different phyla, and group them both under Syndermata., p. 788ff. – see particularly p. 804 This clade is placed in the Platyzoa. Phylogeny Phylogenetic analysis of the 18S ribosomal gene has revealed that the Acanthocephala, formerly considered a separate phylum are most closely related to the rotifers. They are possibly closer to the two rotifer classes Bdelloidea and Monogononta than to the other class, Seisonidea, producing the names and relationships shown in the cladogram below. A study of the gene order in the mitochondria suggests that Seisonidea and Acanthocephala are sister clades and that the Bdelloidea are the sister clade to this group. This has since been corroborated by the discovery of a fossil stem-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotifer
The rotifers (, from Latin 'wheel' and 'bearing'), sometimes called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic Coelom#Pseudocoelomates, pseudocoelomate animals. They were first described by John Harris (writer), Rev. John Harris in 1696, and other forms were described by Antonie van Leeuwenhoek in 1703. Most rotifers are around long (although their size can range from to over ), and are common in freshwater environments throughout the world with a few Seawater, saltwater species. Some rotifers are free swimming and truly planktonic, others move by inchworming along a substrate, and some are Sessility (zoology), sessile, living inside tubes or gelatinous holdfast (biology), holdfasts that are attached to a substrate. About 25 species are colonial (e.g., ''Sinantherina semibullata''), either sessile or planktonic. Rotifers are an important part of the freshwater zooplankton, being a major foodsource and with many specie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotifera
The rotifers (, from Latin 'wheel' and 'bearing'), sometimes called wheel animals or wheel animalcules, make up a phylum (Rotifera ) of microscopic and near-microscopic pseudocoelomate animals. They were first described by Rev. John Harris in 1696, and other forms were described by Antonie van Leeuwenhoek in 1703. Most rotifers are around long (although their size can range from to over ), and are common in freshwater environments throughout the world with a few saltwater species. Some rotifers are free swimming and truly planktonic, others move by inchworming along a substrate, and some are sessile, living inside tubes or gelatinous holdfasts that are attached to a substrate. About 25 species are colonial (e.g., ''Sinantherina semibullata''), either sessile or planktonic. Rotifers are an important part of the freshwater zooplankton, being a major foodsource and with many species also contributing to the decomposition of soil organic matter. Genetic evidence indicates t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Platyzoa
The "Platyzoa" are a group of protostome unsegmented animals proposed by Thomas Cavalier-Smith in 1998. Cavalier-Smith included in Platyzoa the phylum Platyhelminthes (or flatworms), and a new phylum, the Acanthognatha, into which he gathered several previously described phyla of microscopic animals. Later it has been described as paraphyletic, containing the Rouphozoa and the Gnathifera. Since 2022 it is believed that Platyozoa are monophyletic and also includes Mesozoa. Phyla One scheme placed the following phyla in Platyzoa: * Rouphozoa ** Platyhelminthes ** Gastrotricha * Gnathifera ** Syndermata *** Rotifera *** Seisonida ** Acanthocephala ** Gnathostomulida ** Micrognathozoa ** Cycliophora Characteristics None of the Platyzoa groups have a respiration or circulation system because of their small size, flat body or parasitic lifestyle. The Platyhelminthes and Gastrotricha are acoelomate. The other phyla have a pseudocoel, and share characteristics such as the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acanthocephala
Acanthocephala ( Greek , ' 'thorn' + , ' 'head') is a group of parasitic worms known as acanthocephalans, thorny-headed worms, or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host. Acanthocephalans have complex life cycles, involving at least two hosts, which may include invertebrates, fish, amphibians, birds, and mammals. About 1,420 species have been described. The Acanthocephala were long thought to be a discrete phylum. Recent genome analysis has shown that they are descended from, and should be considered as, highly modified rotifers. This unified taxon is sometimes known as Syndermata, or simply as Rotifera, with the acanthocephalans described as a subclass of a rotifer class Hemirotatoria. History The earliest recognisable description of Acanthocephala – a worm with a proboscis armed with hooks – was made by Italian author Francesco Redi (1684). In 1771 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gnathifera (clade)
Gnathifera (from the Greek language, Greek ''wikt:γνάθος#Greek, gnáthos'', “jaw”, and the Latin ''wikt:-fer#Latin, -fera'', “bearing”) is a clade of generally small spiralians characterized by complex jaws made of chitin. It comprises the phyla Gnathostomulida, Rotifera and Micrognathozoa. Chaetognatha has recently been recognised as closely related to the group, with it either being included within Gnathifera or the broader group Chaetognathifera. Gnathiferans include some of the most abundant phyla. Rotifers are among the most diverse and abundant freshwater animals and chaetognaths are among the most abundant marine plankton. Description In most gnathiferans, the anus opens on the dorsal surface of the animal. In micrognathozoans and gnathostomulids, the anus is transient and only forms during defecation. Unlike other gnathiferans, in chaetognaths and the extinct ''Amiskwia'' the anus is located on the ventral surface in a subterminal position. Both Gnatho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylum (biology)
In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent. Depending on definitions, the animal kingdom Animalia contains about 31 phyla, the plant kingdom Plantae contains about 14 phyla, and the fungus kingdom Fungi contains about eight phyla. Current research in phylogenetics is uncovering the relationships among phyla within larger clades like Ecdysozoa and Embryophyta. General description The term phylum was coined in 1866 by Ernst Haeckel from the Greek (, "race, stock"), related to (, "tribe, clan"). Haeckel noted that species constantly evolved into new species that seemed to retain few consistent features among themselves and therefore few features that distinguished them as a group ("a self-contained unity"): "perhap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribosome
Ribosomes () are molecular machine, macromolecular machines, found within all cell (biology), cells, that perform Translation (biology), biological protein synthesis (messenger RNA translation). Ribosomes link amino acids together in the order specified by the codons of messenger RNA molecules to form polypeptide chains. Ribosomes consist of two major components: the small and large ribosomal subunits. Each subunit consists of one or more ribosomal RNA molecules and many ribosomal proteins (). The ribosomes and associated molecules are also known as the ''translational apparatus''. Overview The sequence of DNA that encodes the sequence of the amino acids in a protein is transcribed into a messenger RNA (mRNA) chain. Ribosomes bind to the messenger RNA molecules and use the RNA's sequence of nucleotides to determine the sequence of amino acids needed to generate a protein. Amino acids are selected and carried to the ribosome by transfer RNA (tRNA) molecules, which enter the riboso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monogononta
Monogononta is a class of rotifers, found mostly in freshwater but also in soil and marine environments. They include both free-swimming and Sessility (zoology), sessile forms. Monogononts generally have a reduced Rotifer#Anatomy, corona, and each individual has a single gonad, which gives the group its name. Males are generally smaller than females, and are produced only during certain times of the year, with females otherwise reproducing through parthenogenesis. Their wikt:mastax, mastax is not designed for grinding. They produce mictic and amictic eggs. The class contains 1,570 species. Females are always diploid, and males are haploid. Diploid females produce two types of eggs. One type give rise to new females like themselves, and another that give rise to females that only produce haploid eggs. These will develop into males. When males, through hypodermic impregnation, inject sperm into the body cavity of females carrying a haploid egg, the fertilized egg will develop in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seisonidea
Seisonidae is a family of rotifers, found on the gills of '' Nebalia'', a marine crustacean. Peculiar among rotifers, they are gonochoric; males and females are both present and are equal in size. Both genders are similar with paired gonads. It is considered to have diverged from the other rotifers early on, and in one treatment is placed in a separate class Seisonoidea. They have a large and elongate body with reduced corona. Their muscular system is similar to that of other rotifers: they have longitudinal muscles as well as open annular muscles. Being attached for most of their life, they are semi-sessile, but are capable of detaching and crawl short distances if required. Feeding has never been observed directly, but the stomach in ''Seison nebaliae'' contained bacteria, while a substance that probably represents hemolymph of the ''Nebalia'' host was found in the stomach of ''Paraseison annulatus''. The latter prefer to settle beneath the carapace on the gills of the host's l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cladogram
A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not show how ancestors are related to descendants, nor does it show how much they have changed, so many differing evolutionary trees can be consistent with the same cladogram. A cladogram uses lines that branch off in different directions ending at a clade, a group of organisms with a last common ancestor. There are many shapes of cladograms but they all have lines that branch off from other lines. The lines can be traced back to where they branch off. These branching off points represent a hypothetical ancestor (not an actual entity) which can be inferred to exhibit the traits shared among the terminal taxa above it. This hypothetical ancestor might then provide clues about the order of evolution of various features, adaptation, and other e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
