''Epithemia'' is a genus of

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

s belonging to the family Rhopalodiaceae. The genus has

cosmopolitan distribution In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and en ...

and are found in freshwater and marine ecosystems. Recent studies have proposed that the genus ''Rhopalodia'' should be recategorized to join ''Epithemia'' based on

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

evidence, although this change in nomenclature has been disputed. Members of this genus have

endosymbionts An endosymbiont or endobiont is an organism that lives within the body or cells of another organism. Typically the two organisms are in a mutualistic relationship. Examples are nitrogen-fixing bacteria (called rhizobia), which live in the root ...

that fix nitrogen called spheroid bodies, that are derived from

cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...

. This endosymbiont is closely related to the

nitroplast A nitroplast is an organelle found in certain species of algae, particularly in the marine algae ''Braarudosphaera bigelowii''. It plays a crucial role in nitrogen fixation, a process previously thought to be exclusive to bacteria and archaea. Th ...

organelle. Because of this close relationship, ''Epithemia'' has been proposed as a model system to study the early stages of organelle evolution. Because of their nitrogen fixing endosymbionts, they can be a possible indicator of eutrophication, because ''Epithemia'' abundance decreased with increased ambient inorganic N concentrations.

Species

Those marked with a * were previously in the genus ''Rhopalodia.'' *''Epithemia adnata'' (Kützing) Brébisson, 1838 *'' Epithemia alpestris'' *'' Epithemia alpestris'' *'' Epithemia anasthasiae'' *''Epithemia argus'' (Ehrenberg) Kützing 1844 *''Epithemia catenata'' *''Epithemia constricta'' W. Smith (Krammer)* *'' Epithemia gibba'' * *''Epithemia gibberula'' * *''Epithemia musculus'' * *''Epithemia pelagica'' *''Epithemia reicheltii'' Schmidt et al. 1904 *''Epithemia smithii'' Carruthers 1864 *'' Epithemia sorex'' *'' Epithemia turgida''

References

External links

Diatoms of North America Epithemia page

Algae Base Epithemia page
{{Taxonbar, from=Q1347445 Diatoms Diatom genera