''Spinoclosterium'' 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

Closteriaceae The Closteriaceae are one of four families of Charophyte green algae in the order Desmidiales (desmids). It contains two genera, '' Closterium'' and '' Spinoclosterium''. Description Closteriaceae consists of individual cells that are longer tha ...

.See the

NCBI The National Center for Biotechnology Information (NCBI) is part of the National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The NCBI is loca ...

br>webpage on Spinoclosterium
Data extracted from the It is rare, but widely distributed in freshwater regions throughout the world.

Description

''Spinoclosterium'' consists of solitary cells. Cells are relatively large, flattened, and are crescent-shaped in outline. The midregion is somewhat widened. The apices are broadly rounded to subcapitate, and are furnished with a stout, straight spine. Cells consist of two symmetrical halves, called semicells. Each semicell contains a single, axial

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 ...

containing several

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 ...

s scattered throughout. Each cell apex contains a

vacuole A vacuole () is a membrane-bound organelle which is present in Plant cell, plant and Fungus, fungal Cell (biology), cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water ...

. With its crescent-shaped cells, ''Spinoclosterium'' is similar to its sister genus ''

Closterium ''Closterium'' is a genus of desmid, a group of charophyte green algae.See the NCBIbr>webpage on Closterium Data extracted from the It is placed in the family Closteriaceae. Species of ''Closterium'' are a common component of freshwater microal ...

'', but is easily distinguished by the tips of the cells bearing a spine.

Reproduction

''Spinoclosterium'' is able to reproduce asexually and sexually. It is unusual for its mode of asexual cell division, which involves a pale pink granular

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 ...

. The cell secretes this mucilage in a ring around its midregion, then completes

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 ...

and divides into two daughter cells. Like other

desmid Desmidiales, commonly called the desmids (''Gr.'' ''desmos'', bond or chain), are an Order (biology), order in the Charophyta, a division of green algae in which the land plants (Embryophyta) emerged. Desmids consist of single-celled (sometimes fi ...

s, the two daughter cells are asymmetrical at this stage, with one adult semicell and one newly formed semicell. However, the mucilage holds the two cells roughly in place until cells are fully developed in size. This means that unlike other desmids that finish cell division with daughter cells aligned head-to-head, the daughter cells of ''Spinoclosterium'' are aligned side-to-side. Sexual reproduction is

anisogamous Different forms of anisogamy: A) anisogamy of motile cells, B) 283x283px Anisogamy is a form of sexual reproduction">egg cell">oogamy (egg cell and sperm cell), C) anisogamy of non-motile cells (egg cell and spermatia).">283x283px Anisogamy is ...

, with male and female gametes. Cells reproduce sexually by conjugating. The female cell lies next to the male cell and the two form a tube between them. The

protoplast Protoplast (), is a biology, biological term coined by Johannes von Hanstein, Hanstein in 1880 to refer to the entire cell, excluding the cell wall. Protoplasts can be generated by stripping the cell wall from plant, bacterium, bacterial, or f ...

of the male cell shrinks inside and moves through the tube into the female cell, forming a

zygote A zygote (; , ) is a eukaryote, eukaryotic cell (biology), cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individ ...

. The zygote matures into a full

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 ...

after a few days; the zygospore is irregularly ellipsoid in shape. When the zygospore germinates, it releases its contents and

meiosis Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one c ...

occurs, of which two of the four meiotic producte survive and the other two are aborted. The post-meiotic cells (called two gones) form an additional cell wall, and finally the each gone divides into two asymmetrical juvenile cells, releasing the cells by gelatinization of the double cell wall.

References

External links

*
AlgaTerra database

Index Nominum Genericorum
{{Taxonbar, from=Q7577638 Desmidiales Charophyta genera