Sphaeropleales is an order of

green alga The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...

e that used to be called

Chlorococcales Chlorococcales is a formerly recognized order of green algae in the class Chlorophyceae. , the type family Chlorococcaceae was placed in the order Chlamydomonadales. Conventionally, many groups of coccoid green algae were lumped in the order Ch ...

. The order includes some of the most common freshwater

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic algae such as ''

Scenedesmus ''Scenedesmus'' is a genus of green algae, in the class Chlorophyceae. They are colonial and non-motile. Taxonomy Currently, there are 74 taxonomically accepted species of ''Scenedesmus''. Additionally, several subgenera have been identified, ...

'' and ''

Pediastrum ''Pediastrum'' is a genus of green algae, in the family Hydrodictyaceae. It is a photoautotrophic, nonmotile coenobial (fixed number of cells) green algae that inhabits freshwater environments. Morphology ''Pediastrum'' is a genus usually lo ...

''. The Spaeropleales includes vegetatively non-motile

unicellular A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...

or colonial taxa that have biflagellate

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or mo ...

s with

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

that are directly opposed in direction (the DO arrangement): '' Sphaeroplea'', '' Atractomorpha'', '' Neochloris'', ''

Hydrodictyon The water net (genus ''Hydrodictyon'') is a taxon of freshwater green algae in the family Hydrodictyaceae. ''Hydrodictyon'' does well in clean, eutrophic water, and has become a nuisance in New Zealand, where it has been recently introduced. Th ...

'', and ''

''. All of these taxa have basal body core connections. With an increase in the number of taxa for which sequence data are available, there is evidence of an expanded DO clade that includes additional zoosporic ('' Bracteacoccus'', '' Schroederia'') and some strictly autosporic genera such as ''

Ankistrodesmus ''Ankistrodesmus'' 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 a ...

'', ''

'', '' Selenastrum'', and '' Monoraphidium''. The filamentous '' Microspora'' has been allied with the coccoid genus ''Bracteacoccus'' based on molecular data. Monophyly of the DO clade is supported by phylogenetic analysis of multi-gene data.

References

Chlorophyta orders {{Chlorophyceae-stub