''Tetraedron'' 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 family

Hydrodictyaceae Hydrodictyaceae is a family of green algae in the order Sphaeropleales. They are found in freshwater habitats worldwide. Members of this family are either unicellular or colonial. Cells are cylindrical, polyhedral, spherical, or sometimes nearly ...

. It may also be spelled as ''Tetraëdron''.

Description

''Tetraedron'' consists of single, free-floating cells, making them

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater Aquatic ecosystem, ecosystems. The name comes from the Greek language, Greek words (), meaning 'plant', and (), mea ...

. They are flattened, triangular, quadrangular, or irregularly polygonal in shape; old cells are nearly spherical. The

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

is finely granulated when viewed with a

light microscope The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible spectrum, visible light and a system of lens (optics), lenses to generate magnified images of small objects. Optical microscopes ...

. Cells contain a single

nucleus Nucleus (: nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucleu ...

and a single

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 ...

which fills the cell; the chloroplast has a single

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 ...

with a starch sheath. ''Tetraedron'' reproduces asexually by

autospore Autospores are a type of spores that are produced by algae to enable asexual reproduction and spread. They are non-motile and non-Flagellated cell, flagellated Aplanospore, aplanospores that are generated within a parent cell and have the same sha ...

s; two, four, or eight autospores are formed in the mother cell and are released by rupture of the parent cell wall. Zoospores and sexual reproduction are unknown.

Taxonomy

''Tetraedron'' is currently placed in the family Hydrodictyaceae. Many species have been placed in this genera, on the basis of their polygonal shapes; however, many have been transferred to other genera. Among the

, the genus ''

Chlorotetraedron ''Chlorotetraedron'' is a genus of green algae, in the family Neochloridaceae. The name may also be written as ''Chlorotetraëdron''. It is found as freshwater plankton or in soil. The genus was first described under the name of ''Pseudotetraedr ...

'' appears similar, but differs from ''Tetraedron'' in its ability to produce

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion in aqueous or moist environments. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Certain zoospores are ...

s. Many species formerly included within the genus ''Tetraedron'' are now understood to be xanthophyte or

eustigmatophyte Eustigmatophytes are a small group (17 genera; ~107 species) of eukaryotic forms of algae that includes marine, freshwater and soil-living species. All eustigmatophytes are unicellular, with coccoid cells and polysaccharide cell walls. Eus ...

algae, groups which are unrelated to ''Tetraedron''. Segregate genera include '' Pseudostaurastrum'', '' Goniochloris'', '' Isthmochloron'', '' Tetraedriella'', '' Tetraplektron'', and others. Most species of ''Tetraedron'' are poorly characterized; only a few are well-defined. * '' T. acutidens'' * '' T. acutum'' * '' T. arthrodesmiforme'' * '' T. asymmetricum'' * '' T. bifidum'' * '' T. bifurcatum'' * '' T. caudatum'' * '' T. conicum'' * '' T. constrictum'' * '' T. crassidens'' * '' T. crassispinum'' * '' T. cruciatum'' * '' T. cruciforme'' * '' T. decussatum'' * '' T. duospinum'' * '' T. floridense'' * '' T. gracile'' * '' T. granulosum'' * '' T. hemisphaericum'' * '' T. hexacornicum'' * '' T. horridum'' * '' T. hortense'' * '' T. lunula'' * '' T. mainensis'' * '' T. mediocris'' * '' T. minimum'' * '' T. minutissimum'' * '' T. multispinosum'' * '' T. obtusum'' * '' T. octaedricum'' * '' T. pachydermum'' * '' T. paraincus'' * '' T. pentaedricum'' * '' T. proteiforme'' * '' T. pulvinus'' * '' T. pusillum'' * '' T. quadricuspidatum'' * '' T. rectangulare'' * '' T. roldanii'' * '' T. sexconicum'' * '' T. simmeri'' * '' T. smithii'' * '' T. spiniferum'' * '' T. staurastroides'' * '' T. striatum'' * '' T. triangulare'' * '' T. trigonum'' * '' T. trilobulatum'' * '' T. tumidulum'' * '' T. valdezii'' * '' T. victoriae'' * '' T. vulgare'' * '' T. wasteneysii''

References

Sphaeropleales genera Sphaeropleales {{Chlorophyceae-stub