''Dictyosphaerium'' 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

Chlorellaceae Chlorellaceae are a family of green algae in the order Chlorellales. About 250 species are currently accepted in the family. Members of the family are distributed worldwide and are common in a variety of freshwater, terrestrial and marine enviro ...

. It occurs 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 around the world and is

planktonic Plankton are the diverse collection of organisms that drift in water (or air) but are unable to actively propel themselves against currents (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they pro ...

. The name comes from the Greek roots ''diktyon'', meaning "net", and ''sphaira'', meaning "ball", referring to its morphology.

Description

''Dictyosphaerium'' consists of irregular colonies of 4 to 64 cells in a common mucilaginous envelope 10–100 μm wide. Cells are roughly spherical to ellipsoidal, 1-10 μm in diameter, with one

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

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 ...

-containing

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 ...

. Cells are attached to the end of thin stalks; the stalks emerge from the center of the colony and continuously branch out. These stalks are formed from the remnants of the mother

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, ...

. ''Dictyosphaerium'' cells reproduce 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 or four autospores are produced per sporangium; after release, the mother cell wall gelatinizes and develops into a thin strand, which are connected to the newly released cells.

Taxonomy

''Dictyosphaerium'' has traditionally been classified in its own family, Dictyosphaeriaceae, or as part of the family

Botryococcaceae Botryococcaceae is a family of green algae in the class Trebouxiophyceae. Traditionally, Botryococcaceae has been defined on morphological grounds. Members of this family consist of irregular colonies of cells found free-floating or attached to ...

, characterized by cells connected by gelatinous stalks or strands of mucilage. However,

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 ...

studies have demonstrated that ''Dictyosphaerium'' is closely related to the unicellular genus ''

Chlorella ''Chlorella'' is a genus of about thirteen species of single- celled or colonial green algae of the division Chlorophyta. The cells are spherical in shape, about 2 to 10 μm in diameter, and are without flagella. Their chloroplasts contain t ...

'', and is now currently placed in the family

. Additionally, the morphotype of ''Dictyosphaerium'' (consisting of branching strands of mucilage connecting cells) is known to be

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

, having evolved multiple times. Therefore, this morphotype can now be found in many new genera. For example, the genus '' Mucidosphaerium'' differs from ''Dictyosphaerium'' ''sensu stricto'' in having spherical cells, as opposed to ''Dictyosphaerium'' with oval cells. The genus '' Mychonastes'' (including the former genus ''Pseudodictyosphaerium'') differs in having chloroplasts without pyrenoids, and more irregular mucilaginous strands. Other similar genera include '' Compactochlorella'', '' Kalenjinia'', '' Marasphaerium'', '' Masaia'', '' Hindakia'', '' Heynigia'', and '' Xerochlorella''. These genera appear to be more or less cryptic, being reliably differentiated only by

DNA barcoding DNA barcoding is a method of species identification using a short section of DNA from a specific gene or genes. The premise of DNA barcoding is that by comparison with a reference library of such DNA sections (also called " sequences"), an indiv ...

. Their biogeographical patterns remain unclear.

References

{{Taxonbar, from=Q5274017 Trebouxiophyceae genera Chlorellaceae Freshwater algae