''Coelastrum'' 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

Scenedesmaceae Scenedesmaceae is a family of green algae in the order Sphaeropleales. ''Scenedesmus'' algae are commonly found in freshwater plankton. The former family Coelastraceae is considered a synonym of Scenedesmaceae. The family has existed since at ...

family. It is a common component of the

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 ...

in freshwater habitats such as ponds, lakes, waterfalls, and temporary pools of water, particularly

eutrophic Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of organisms that may deplete the oxygen in the water; ie. the process of too many plants growing on the s ...

ones. The genus has a more or less

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 ...

, although some species appear to have more restricted geographical distributions. The name comes from the Greek terms ''koilos'', meaning hollow, and ''astron'', meaning star.

Description

''Coelastrum'' consists of round colonies of cells (termed coenobia) of 4, 8, 16, 32, or 64 cells. Cells are spherical to polygonal, and are connected to each other via extensions of their

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, ...

s to form hollow spheres. The cells may have various ornamentation such as protuberans, and have one 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 ...

with 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 ...

. ''Coelastrum'' reproduces asexually. Prior to reproduction, cell nuclei undergo

mitosis Mitosis () is a part of the cell cycle in eukaryote, eukaryotic cells in which replicated chromosomes are separated into two new Cell nucleus, nuclei. Cell division by mitosis is an equational division which gives rise to genetically identic ...

, forming multinucleate cells. The cell then undergoes

cytokinesis Cytokinesis () is the part of the cell division process and part of mitosis during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of nuclear division ...

and a new daughter colony is formed within the parental cell.

Identification

Species of ''Coelastrum'' are distinguished from each other by their morphologies—in particular, their cell size and shape, number of cells per coenobia, and the nature of the ornamentation surrounding the cells and connecting the cells to each other. However, a great deal of morphological variability exists, which complicates

species delimitation A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of classification and a ...

and therefore identification. A similar genus is '' Hariotina'', also part of the subfamily Coelastroideae. ''Hariotina'' can be distinguished by having cells connected by one to three strands at the top (rather than at their base), and by having colonies surrounded by

mucilage Mucilage is a thick gluey substance produced by nearly all plants and some microorganisms. These microorganisms include protists which use it for their locomotion, with the direction of their movement always opposite to that of the secretion of ...

(while ''Coelastrum'' lacks mucilage).

Taxonomy

''Coelastrum'' was once classified as a member of its own family, the Coelastraceae, which has always considered to be similar to the

. With

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

analyses, Scenedesmaceae was found to

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

with respect to Coelastraceae and therefore Coelastraceae placed into Scenedesmaceae as its own

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

, Coelastroideae.

Uses

Species of ''Coelastrum'' have been tested for uses in

biotechnology Biotechnology is a multidisciplinary field that involves the integration of natural sciences and Engineering Science, engineering sciences in order to achieve the application of organisms and parts thereof for products and services. Specialists ...

, such as lipid or

astaxanthin Astaxanthin is a keto- carotenoid within a group of chemical compounds known as carotenoids or terpenes. Astaxanthin is a metabolite of zeaxanthin and canthaxanthin, containing both hydroxyl and ketone functional groups. It is a lipid-solu ...

production and

wastewater treatment Wastewater treatment is a process which removes and eliminates contaminants from wastewater. It thus converts it into an effluent that can be returned to the water cycle. Once back in the water cycle, the effluent creates an acceptable impact on ...

. In

paleoecology Paleoecology (also spelled palaeoecology) is the study of interactions between organisms and/or interactions between organisms and their environments across geologic timescales. As a discipline, paleoecology interacts with, depends on and informs ...

, they serve as a marker for

eutrophication Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of organisms that may deplete the oxygen in the water; ie. the process of too many plants growing on the s ...

Species list

*''

Coelastrum astroideum ''Coelastrum'' is a genus of green algae in the Scenedesmaceae family. It is a common component of the phytoplankton in freshwater habitats such as ponds, lakes, waterfalls, and temporary pools of water, particularly eutrophic ones. The genus ha ...

'' *''

Coelastrum cambricum ''Coelastrum'' is a genus of green algae in the Scenedesmaceae family. It is a common component of the phytoplankton in freshwater habitats such as ponds, lakes, waterfalls, and temporary pools of water, particularly eutrophic ones. The genus ha ...

'' *''

Coelastrum chodatii ''Coelastrum'' is a genus of green algae in the Scenedesmaceae family. It is a common component of the phytoplankton in freshwater habitats such as ponds, lakes, waterfalls, and temporary pools of water, particularly eutrophic ones. The genus ha ...

'' *'' Coelastrum crenatum'' *'' Coelastrum giganteum'' *'' Coelastrum indicum'' *'' Coelastrum irregulare'' *'' Coelastrum microporum'' *'' Coelastrum morus'' *'' Coelastrum naegelii'' *'' Coelastrum printzii'' *'' Coelastrum probiscideum'' *'' Coelastrum pseudomicroporum'' *'' Coelastrum pulchellum'' *''

Coelastrum pulchrum ''Coelastrum'' is a genus of green algae in the Scenedesmaceae family. It is a common component of the phytoplankton in freshwater habitats such as ponds, lakes, waterfalls, and temporary pools of water, particularly eutrophic ones. The genus has ...

'' *'' Coelastrum reticulatum'' *'' Coelastrum schizodermaticum'' *'' Coelastrum sphaericum'' *'' Coelastrum stuhlmanii'' *'' Coelastrum triangulare'' *'' Coelastrum verrucosum''

References

* {{Authority control Sphaeropleales genera Sphaeropleales Freshwater algae