''Sphaerozosma'' 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 ...
of
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 Sphaerozosma]
Data extracted from the It occurs in acidic, oligotrophic
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 and is found worldwide.
[
]
Description
''Sphaerozosma'' consists of cells which are flattened (and thus biradiate in apical view); the cells are attached end-to-end to form short or long filaments. At the apex of each cell there is a pair of obliquely placed, small rod-like processes; cells are attached to each other via these processes. 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, ...
has pores arranged in horizontal or oblique lines. Cells are deeply constricted at the middle, forming two halves (called semicells). Each semicell has 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 ...
with a central 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 ...
. The nucleus is at the isthmus where the two semicells are joined.[
]
Reproduction
Reproduction in ''Sphaerozosma'' can be asexual
Asexual or Asexuals may refer to:
*Asexual reproduction
**Asexual reproduction in starfish
*Asexuality, the lack of sexual attraction to anyone or lack of interest in or desire for sexual activity.
**Gray asexuality, the spectrum between asexualit ...
or sexual. In asexual reproduction, the cell divides and forms new semicells in the same manner as other (''Cosmarium
''Cosmarium'' 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 ''Cosmarium'' co ...
''-type) desmids. After cytokinesis occurs and the new semicells develop, the primary cell wall is shed from all but the apical region, where it remains connecting the daughter cells in the new filament. Sexual reproduction is by conjugation, where filaments disintegrate into individual cells. Zygotes form between cells (=gametangia), and develop into zygospore
A zygospore is a diploid reproductive stage in the life cycle of many fungi and protists. Zygospores are created by the nuclear fusion of haploid cells. In fungi, zygospores are formed in zygosporangia after the fusion of specialized budding stru ...
s. Mature zygospores are spherical, with a smooth cell wall or covered with spines or protuberances.[
]
Taxonomy
The genus '' Onychonema'' is morphologically very similar and sometimes considered to be a synonym of ''Sphaerozosma''. When the two genera are considered separate, ''Onychonema'' differs in having longer, more distantly spaced apical processes.
References
External links
AlgaTerra database
Index Nominum Genericorum
Desmidiaceae
Charophyta genera
{{green algae-stub