''Staurodesmus'' 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 ...

, specifically of the

Desmidiaceae The Desmidiaceae are one of four family (biology), families of Charophyta, charophyte green algae in the order (biology), order Desmidiales (desmids).See the National Center for Biotechnology Information, NCBI]webpage on Desmidiaceae Data extrac ...

.See the National Center for Biotechnology Information, NCBIbr>webpage on Staurodesmus
Data extracted from the

History

The genus ''Staurodesmus'' was first circumscribed by the desmidiologist Einar Teiling. The defining characteristic of the genus is the single, unbranched spines at each angle of the semicell. Cell walls also lack protuberances or other ornamentations, which separate the genus from the similar '' Xanthidium''. The genus includes species formerly placed in ''Arthrodesmus'' and ''

Staurastrum ''Staurastrum'' is a large genus of desmids (Desmidiaceae), a group of green algae closely related to the land plants (Embryophyta). Members of this genus are microscopic and found in freshwater habitats around the world. The name ''Staurastrum'' ...

'', the difference in the two genera being the number of planes of symmetry: ''Arthrodesmus'' was biradiate (having two planes of symmetry), while ''Staurastrum'' included species with three or more planes of symmetry. However, over the years desmidiologists found many specimens with one biradiate semicell and another tri- or quadriradiate semicell. As these cells could not soundly be placed into one genus, Teiling erected ''Staurodesmus''; the name was made to be a

portmanteau In linguistics, a blend—also known as a blend word, lexical blend, or portmanteau—is a word formed by combining the meanings, and parts of the sounds, of two or more words together.

of ''Arthrodesmus'' and ''Staurastrum''. Although ''Staurastrum'' is still used as a genus, ''Arthrodesmus'' is a later

homonym In linguistics, homonyms are words which are either; '' homographs''—words that mean different things, but have the same spelling (regardless of pronunciation), or '' homophones''—words that mean different things, but have the same pronunciat ...

(thus invalid) and is no longer used.

Description

''Staurodesmus'' consists of solitary cells that are divided into two symmetrical halves, called semicells. Semicells are diverse in shape, but are unified by having a single, unbranched spine at the angles of the semicells. 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 smooth and lacks ornamentations other than pores or fine granules. Each semicell contains 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 ...

. Species of ''Staurodesmus'' are distinguished from each other by the shape of the cells, and the size and orientation of the spines.

References

External links

*
AlgaTerra database

Index Nominum Genericorum
Desmidiaceae Charophyta genera {{green algae-stub