The bdelloids (Bdelloidea) are a class of rotifers, found in freshwater and moist soil. Bdelloids (pronounced with an mouthed and almost silent B rather like "deltoids" with a silent 't') typically have a well developed corona, divided into two parts, on a retractable head. They may move by swimming or crawling. The latter commonly involves taking alternate steps with the head and tail, as do certain leeches, which gives the group their name (Greekβδελλα or bdella, meaning leech). Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms. ... Phyla Subregnum Parazoa Porifera (sponges) Subregnum Agnotozoa Placozoa (trichoplax) Orthonectida (orthonectids) Rhombozoa (dicyemids) Subregnum Eumetazoa Radiata (unranked) (radial symmetry) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anemones) Bilateria (unranked) (bilateral symmetry) Acoelomorpha (basal) Myxozoa (slime animals) Superphylum Deuterostomia (blastopore becomes anus) Chordata (vertebrates, etc. ... Classes Seisonoidea Bdelloidea Monogononta The rotifers make up a phylum of microscopic, and near-microscopic pseudocoelomate animals. ... Classes Seisonoidea Bdelloidea Monogononta The rotifers make up a phylum of microscopic, and near-microscopic pseudocoelomate animals. ... Orders Arhynchobdellida or Rhynchobdellida There is some dispute as to whether Hirudinea should be a class itself, or a subclass of the Clitellata. ...
Bdelloids have been of interest to those interested in the evolutionary role of sexual reproduction, because it has disappeared entirely from the group: males are unknown, and females reproduce exclusively by parthenogenesis. Each individual has paired gonads. Sexual reproduction is a type of reproduction that results in increasing genetic diversity of the offspring. ... Kaguya is one success from 460 attempts at growing embryos. ... The gonad is the organ that makes gametes. ...
Bdelloids respond to environmental stresses by entering a state of dormancy known as anhydrobiosis. This dormancy form enables the organism to rapidly dehydrate itself.The Bdelloid will remain in this cysted state until optimal environmental conditions re-occur at which point they will rehydrate and become active within hours. Diapause is the ability of the organism to produce offspring in a dormant and unhatched state. Hatching of the young will only occur when conditions are at their most favourable. These forms of dormancy are also known as cryptobiosis or quiescence. 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. ...
Bdelloidrotifers have relatively uniform structure of body adapted to life, in spatially restricted water film of edaphon, in mosses, lichens, leaf and fir litter where they are mostly spread and also in the littoral and profundal of fresh waters, in benthos and among aquatic vegetation.
Therefore it can be assumed that obligatory parthenogenetic bdelloidrotifers invaded terrestrial biotopes on the early stage of their evolution; they are characterized by slow evolution rates as compared to heterogonetic monogononts; the variability of bdelloids is of principally of different character and concerns morphological structures of a lower taxonomic rank.
Kutikova, L.A. Kolovratki fauny SSSR [The rotifer fauna of USSR].
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