''Brachionus'' is a genus of planktonic

rotifer The rotifers (, from the Latin , "wheel", and , "bearing"), commonly 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 H ...

s occurring in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

alkaline In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a base (chemistry), basic, ionic compound, ionic salt (chemistry), salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as ...

and brackish water.

Species

Species included in ''Brachionus'' include: * ''

Brachionus amsterdamensis ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * '' Brachionus amsterdamensis'' De Smet, 2001 * '' Brachionus angularis'' Gosse, 1851 * ...

'' De Smet, 2001 * ''

Brachionus angularis ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * ''Brachionus amsterdamensis'' De Smet, 2001 * '' Brachionus angularis'' Gosse, 1851 * ...

'' Gosse, 1851 * ''

Brachionus asplanchnoides ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * ''Brachionus amsterdamensis'' De Smet, 2001 * ''Brachionus angularis'' Gosse, 1851 * ' ...

'' Charin, 1947 * '' Brachionus calyciflorus'' Pallas, 1766 * ''

Brachionus diversicornis ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * ''Brachionus amsterdamensis'' De Smet, 2001 * ''Brachionus angularis'' Gosse, 1851 * ...

'' (Daday, 1883) * ''

Brachionus havanaensis ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * '' Brachionus amsterdamensis'' De Smet, 2001 * '' Brachionus angularis'' Gosse, 1851 * ...

'' Rousselet, 1911 * ''

Brachionus ibericus ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * '' Brachionus amsterdamensis'' De Smet, 2001 * '' Brachionus angularis'' Gosse, 185 ...

'' Ciros-Peréz, Gómez & Serra, 2001 * ''

Brachionus leydigii ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * ''Brachionus amsterdamensis'' De Smet, 2001 * ''Brachionus angularis'' Gosse, 1851 * ' ...

'' Cohn, 1862 * ''

Brachionus manjavacas ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * '' Brachionus amsterdamensis'' De Smet, 2001 * '' Brachionus angularis'' Gosse, 1851 * ...

'' Fontaneto, Giordani, Melone & Serra, 2007 * ''

Brachionus nilsoni ''Brachionus nilsoni'' is a euryhaline (tolerates a wide range of salinity) rotifer in the family ''Brachionidae''. The species is distinguishable from all brachionids by lacking posterior spines, by the shape of the foot apertures and the post ...

'' Ahlstrom * '' Brachionus plicatilis'' Müller, 1786 * ''

Brachionus quadridentatus ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * '' Brachionus amsterdamensis'' De Smet, 2001 * '' Brachionus angularis'' Gosse, 185 ...

'' Hermann, 1783 * ''

Brachionus rotundiformis ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * '' Brachionus amsterdamensis'' De Smet, 2001 * '' Brachionus angularis'' Gosse, 185 ...

'' Tschugunoff, 1921 * ''

Brachionus rubens ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * '' Brachionus amsterdamensis'' De Smet, 2001 * '' Brachionus angularis'' Gosse, 185 ...

'' Ehrenberg, 1838 * ''

Brachionus urceolaris ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * '' Brachionus amsterdamensis'' De Smet, 2001 * '' Brachionus angularis'' Gosse, 185 ...

'' Müller, 1773 * ''

Brachionus variabilis ''Brachionus'' is a genus of planktonic rotifers occurring in freshwater, alkaline and brackish water. Species Species included in ''Brachionus'' include: * '' Brachionus amsterdamensis'' De Smet, 2001 * '' Brachionus angularis'' Gosse, 185 ...

'' Hempel, 1896

Use

Rotifers such as ''Brachionus calyciflorus'' are favored test animals in aquatic toxicology because of their sensitivity to most toxicants. They also are used as model organisms in various other biological fields e.g. due to their interesting reproductive mode in evolutionary ecology. Brachionus spp. are easily reared in large numbers and because of this are used to substitute for wild zooplankton for feeding hatchery reared larval fish. However, the composition of rotifers generally does not satisfy the nutritional requirements of fish larvae, and large amounts of research have been invested in improving the lipid, vitamin and mineral composition of rotifers to better meet the requirements of fish larvae

Reproduction

Brachionus species can normally reproduce sexually and asexually (cyclical parthenogenesis). Sexual reproduction (termed

Mixis ''Pleurothallis'' is a genus of orchids commonly called bonnet orchids. The genus name is derived from the Greek word , meaning "riblike branches". This refers to the rib-like stems of many species. The genus is often abbreviated as "Pths" in hor ...

) is usually induced when population density increases. Mixis in '' Brachionus plicatilis'' has been shown to be induced by a density-dependent chemical cue. Transitions to obligate parthenogenesis have been described in '' Brachionus calyciflorus''. In this species, obligate parthenogenesis can be inherited by a recessive allele, which leads to loss of sexual reproduction in homozygous offspring. In ''Brachionus manjavacas'' rotifers, offspring's survival and its cell's ability to growth and division decrease with advancing age of mother.

Genome size

Haploid '1C' genome sizes in Brachionus species range at least from 0.056 to 0.416 pg.

Genome sequencing

The complete mitochondrial genome of ''B. plicatilis'' sensu stricto NH1L has been sequenced.

Cryptic species

'' Brachionus plicatilis'' has been demonstrated to be a large cryptic species complex consisting of several different species. It has a worldwide diversity of at least 14 - 22 cryptic taxa. '' Brachionus calyciflorus'' also seems to be a cryptic species complex.Brachionus calyciflorus is a species complex: mating behavior and genetic differentiation among four geographically isolated strains JJ Gilbert, EJ Walsh - Rotifera X, 2005 - Springer

References

Huang, L. "Effectof Aldrin on Life History Characteristics of Rotifer Brachionus calyciflorus Pallas." Bull Environ Contam Toxicol no5 N 2007 {{Taxonbar, from=Q3516967 Rotifer genera Brachionidae