''Goniomonas'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

Cryptomonads The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anteri ...

and contains five species. It is a genus of single-celled eukaryotes, including both freshwater and marine species. It lacks

plastids The plastid (Greek: πλαστός; plastós: formed, molded – plural plastids) is a membrane-bound organelle found in the cells of plants, algae, and some other eukaryotic organisms. They are considered to be intracellular endosymbiotic cyanobac ...

, which is very unusual among all of the Cryptophyte genera. It may reflect one of only a small number of times that the Cryptophytes evolved into freshwater habitats. ''Goniomonas'' seems to have a number of freshwater relatives which have not yet been cultured and named.

Etymology

''Goniomonas'' means angled small flagellates, combining ''goni'' and ''monas''.

History of Discovery

It was established by German biologist

Samuel Friedrich Stein Samuel Friedrich Nathaniel Ritter von Stein (November 3, 1818 – January 9, 1885) was a German entomologist. He was Professor at the Royal Saxon Academy of Forestry in Tharandt from 1850–55; and Professor, and later Rector, at the Charles Unive ...

in 1878.

Morphology

This genus contains species that are free-swimming, flattened, biflagellate monads. They are oval in lateral view with an obliquely truncate anterior. A furrow extends along the middle of the anterior margin and for a short distance down the ventral margin and is surrounded by a single lateral row of ejectisomes.

Chloroplasts A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...

, pyrenoids, nucleomorphs and starch are absent. They have

periplast The periplast is one of three types of cell-covering of three classes of algae. The ''Cryptomonads'' have the periplast covering. The '' Dinophyceae'' have a type called the amphiesma, and the ''Euglena'' covering is the pellicle. Structure The pe ...

with longitudinal striations visible in all species. And, ''Goniomonas'' is the only Cryptomonad so far examined that does not possess a plastidial complex, and is therefore considered primitive among Cryptophytes. Other Cryptophytes have bipartite tubular flagellar hairs, whereas ''Goniomonas'' has solid spike-like flagellar projections. The furrow-gullet system of ''Goniomonas'' is located on the anterior of the cell rather than the usual ventral location.

Reproduction

Cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble) ...

production is not known in this genus.

Ecology

The genus is well known in freshwater habitats with a cosmopolitan distribution, but is rarely abundant. It is also present in marine waters. The temperatures and specific depths suitable for the species are not recorded.

Genetics

Only one freshwater and two marine species have been extensively described so far. Marine species are ''G. pacifica'' and ''G. amphinema'', while ''G. truncata'' is a freshwater species. Although the two marine species are morphologically quite distinct from each other, it was unclear until recently whether one of them, ''G. pacifica'', is really separate from the freshwater ''G. truncata'' because their morphology and size are similar. Results reveal remarkable genetic diversity within all three nominal species and confirm that ''G. pacifica'' is genetically very distinct from ''G. truncata.'' Scientists suggest that if further studied, ''Goniomonads'' might turn out to have as many ‘species’ as Cryptophytes. They reproduce by asexual reproduction as current research concludes. Further studies can focus on whether ''Goniomonads'' are sexual. And, it is still to determine whether the biological species concept can be applied to them.

List of Species

The following is a list of species. * '' Goniomonas amphinema'' Larsen & Patterson, 1990 * '' Goniomonas avonlea'' Kim & Archibald, 2012 * '' Goniomonas elongata'' Maskell, 1888 * '' Goniomonas pacifica'' Larsen & Patterson, 1990 * '' Goniomonas truncata'' (Fresenius) Stein, 1878

References

{{Cryptista Cryptomonad genera