''Spermatozopsis'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

in the class

Chlorophyceae The Chlorophyceae, also known as chlorophycean algae, are one of the classes of green algae, within the phylum Chlorophyta. They are a large assemblage of mostly freshwater and terrestrial organisms; many members are important primary producers i ...

. It is found 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. The term excludes seawater and brackish water, but it does include non-salty mi ...

habitats; it is widespread but not common. ''Spermatozopsis'' consists of single, flagellated cells. Cells are 7–10(–12) μm wide long and 2–4 μm long, fusiform, curved (one side convex, the other side concave) and sometimes twisted. The anterior of the cell has two or four

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

, which are longer than the cell, with two

contractile vacuole A contractile vacuole (CV) is a sub-cellular structure (organelle) involved in osmoregulation. It is found predominantly in protists, including unicellular algae. It was previously known as pulsatile or pulsating vacuole. Overview The contrac ...

s near the base of the flagella. The cell has a single parietal

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

along the convex side of the cell with a stigma, lacking a

pyrenoid Pyrenoids are sub-cellular phase-separated micro-compartments found in chloroplasts of many algae,Giordano, M., Beardall, J., & Raven, J. A. (2005). CO2 concentrating mechanisms in algae: mechanisms, environmental modulation, and evolution. ''An ...

. Asexual reproduction occurs by longitudinal binary fission. ''Spermatozopsis'' swims with in a spiral motion, with its anterior in the front and its flagella oriented backwards. Cells can also jerk backwards by pushing their flagella forwards. ''Spermatozopsis'' is able to produce microbial cysts, which are globose with several parietal chloroplasts. Motile cells are able to withstand temperatures as high as 35 °C, and cysts can withstand dry heat; these traits likely help ''Spermatozopsis'' survive in aquatic environments. It serves as prey for

dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

species. The

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 ...

position of ''Spermatozopsis'' is unclear. Although it is traditionally a member of Dunaliellaceae based on morphology,

phylogenomic Phylogenomics is the intersection of the fields of evolution and genomics. The term has been used in multiple ways to refer to analysis that involves genome data and evolutionary reconstructions. It is a group of techniques within the larger fields ...

studies place ''Spermatozopsis'' as either within Chlamydomonadales/Volvocales or as basal to the rest of

Sphaeropleales Sphaeropleales is an order of green algae that used to be called Chlorococcales. The order includes some of the most common freshwater plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphe ...

Species

Two species are known. The first is '' Spermatozopsis exsultans'', which has four flagella of equal length (occasionally two or eight during division stages). The second is '' Spermatozopsis similis'', which has two subequal flagella. A third species was discovered and named ''Spermatozopsis acidophila'', but because of its morphological and ultrastructural differences (such as possessing a pyrenoid), it was transferred to the genus ''

Dunaliella ''Dunaliella'' is a single-celled, photosynthetic Green algae, green alga, that is characteristic for its ability to outcompete other organisms and thrive in Hypersaline lake, hypersaline environments. It is mostly a marine organism, though there ...

''.

References

Chlamydomonadales genera Chlamydomonadales Freshwater algae {{Chlorophyceae-stub