''Asterococcus'' 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 ...
in the order
Chlamydomonadales
Chlamydomonadales, also known as Volvocales, are an order of flagellated or pseudociliated green algae, specifically of the Chlorophyceae.See the NCBIbr>webpage on Chlamydomonadales Data extracted from the Chlamydomonadales can form planar o ...
.
It 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 ...
in freshwater ponds and lakes, or
benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...
within mires and swamps. It is a common and widespread genus, but is rarely abundant.
[
]
Taxonomy
The botanist Leon Cienkowski was the first to observed organisms now assigned to ''Asterococcus'', when he described the taxon ''Pleurococcus superbus'' in 1865. Later in 1908, Aladár Scherffel transferred that species into a new genus, and named it ''Asterococcus''.monophyletic
In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria:
# the grouping contains its own most recent co ...
. Currently, taxonomic databases such as AlgaeBase
AlgaeBase is a global species database of information on all groups of algae, both seaweed, marine and freshwater algae, freshwater, as well as sea-grass.
History
AlgaeBase began in March 1996, founded by Michael D. Guiry, Michael Guiry. Text ...
place this genus in the family Palmellopsidaceae. 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 ...
s have demonstrated that it is most closely related to some species of ''Carteria
''Carteria'' is a genus of green algae in the family Chlamydomonadaceae. ''Carteria'' are similar in morphology to the common genus '' Chlamydomonas'' and differ by having four, rather than two, flagella at the vegetative stage.
The genus name ...
'', such as '' Carteria radiosa''.[
]
Description
''Asterococcus'' consists of colonies in powers of two (two, four, eight, 16, rarely up to 64), or occasionally single cells, embedded within a conspicuous, often layered mucilaginous envelope. The cells are usually spherical to ellipsoidal and are either dispersed in the envelope or attached to the end of a branched (dendroid), mucilaginous stalk. Cells are 10–40 μm in diameter with smooth 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, a single 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 usually with two contractile vacuole
A contractile vacuole (CV) is a sub-cellular structure (organelle) involved in osmoregulation. It is found predominantly in protists, including unicellular algae. It was previously known as pulsatile or pulsating vacuole.
Overview
The contrac ...
s. Cells contain 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 ...
in the center of the cell 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 ...
, with numerous radiating lobes flattened against the cell wall.[
Reproduction in ''Asterococcus'' occurs asexually by the formation of ]