''Artemia parthenogenetica'' is a species of

brine shrimp ''Artemia'' is a genus of aquatic crustaceans also known as brine shrimp or ''Sea-Monkeys, sea monkeys''. It is the only genus in the Family (biology), family Artemiidae. The first historical record of the existence of ''Artemia'' dates back to t ...

– aquatic

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

s belonging to a different class, the Branchiopoda, than the true

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

Taxonomy

The name ''Artemia parthenogenetica'' is widely used in the relevant literature, although some taxonomists regard it as being used incorrectly to refer to parthenogenetic populations of ''Artemia'' that do not form a true species. A 2015 study based on

microsatellite A microsatellite is a tract of repetitive DNA in which certain Sequence motif, DNA motifs (ranging in length from one to six or more base pairs) are repeated, typically 5–50 times. Microsatellites occur at thousands of locations within an organ ...

markers showed that

parthenogenetic Parthenogenesis (; from the Greek + ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means the development of an embryo from an unfertiliz ...

populations of different

ploidy Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

levels group together in a

principal component analysis Principal component analysis (PCA) is a linear dimensionality reduction technique with applications in exploratory data analysis, visualization and data preprocessing. The data is linearly transformed onto a new coordinate system such that th ...

, and are distinct from related species such as '' Artemia sinica'', ''

Artemia tibetiana ''Artemia'' is a genus of aquatic crustaceans also known as brine shrimp or '' sea monkeys''. It is the only genus in the family Artemiidae. The first historical record of the existence of ''Artemia'' dates back to the first half of the 10th cent ...

'' and '' Artemia urmiana''.

Description

''A. parthenogenetica'' is an obligate parthenogenetic organism that is found in Europe, Africa, and Asia, from the

Canary Islands The Canary Islands (; ) or Canaries are an archipelago in the Atlantic Ocean and the southernmost Autonomous communities of Spain, Autonomous Community of Spain. They are located in the northwest of Africa, with the closest point to the cont ...

in the far west of its known range, east to Australia. It lives in hypersaline water bodies mostly along coastal waters of these continents. In Australia, scientists are debating whether the organism is native or introduced from birds. In inland Australia, genetic information indicates that populations have been introduced by migratory birds. As ''A. parthenogenetica'' can more favorably survive in high salinities, when large bodies of water dry out, the introductions of cysts by migrating birds from coastal regions may allow populations to become established, as happened in the

South Aral Sea The South Aral Sea is a lake in the basin of the former Aral Sea that formed in 1987 when that body divided in two, due to diversion of river inflow for agriculture. In 2003, the South Aral Sea itself split into eastern and western basins, the ...

in the late 1990s.

Life cycle

''A. parthenogenetica'', as its

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

suggests, is an obligate

organism, one that reproduces without sexual reproduction. Like other brine shrimp, ''A. parthenogenetica'' produces cysts that are highly resistant to environmental changes, including large changes in temperature and salinity, and the stress of drying out and exposure to UV radiation. The organism displays different numbers of chromosomes or levels of

, from diploid to 5n. ''A. parthenogenetica'' populations with 2n ploidy have some recombination of genes during

meiosis Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one c ...

then fuse the recombined cells to regain the 2n chromosomes. In populations with ploidies from 3n to 5n, the resultant offspring are clones of the parents.

Automixis

Diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

''A. parthenogenetica'' can undergo

, but instead of producing haploid

gamete A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...

s as ordinarily occurs in sexual species, diploid meiotic products are most often produced by

automixis Automixis is the fusion of (typically haploid) nuclei or gametes derived from the same individual. The term covers several reproductive mechanisms, some of which are parthenogenetic. Diploidy might be restored by the doubling of the chromosomes ...

. Automixis involves the fusion of nuclei derived from the same individual meiosis. The specific type of automixis occurring in ''A. partheogenetica'' is likely “central fusion”, that is fusion of the first two meiotic products (see Figure in

Automixis Automixis is the fusion of (typically haploid) nuclei or gametes derived from the same individual. The term covers several reproductive mechanisms, some of which are parthenogenetic. Diploidy might be restored by the doubling of the chromosomes ...

). Automixis allows ''A. parthenogenetica'' to reproduce parthenogenetically. However, despite its species designation as “''parthenogentica''” implying obligate parthenogenesis, recent evidence indicates that this species is also capable of infrequently reproducing sexually.

References

{{Taxonbar, from=Q4553244 Anostraca Crustaceans described in 1978