''Microthamnion'' 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 family
Microthamniaceae.
It is found 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, preferably with low levels of pollution;
[ it is typically attached to solid substrates.][
]
Description
''Microthamnion'' consists of a microscopic, branched system of erect filaments. The filaments are uniseriate, with cylindrical cells; terminal cells are obtuse. Cells range from 1-5 μm wide and 2-15 times longer than wide.[ New branches form just underneath the cross-walls connecting cells. Cells are uninucleate (i.e. 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 ...
with a parietal 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 ...
and no visible 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.zoospore
A zoospore is a motile asexual spore that uses a flagellum for locomotion in aqueous or moist environments. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Certain zoospores are ...
s, which are formed in vegetative cells that develop into sporangia
A sporangium (from Late Latin, ; : sporangia) is an enclosure in which spores are formed. It can be composed of a unicellular organism, single cell or can be multicellular organism, multicellular. Virtually all plants, fungus, fungi, and many ot ...
. Typically this occurs in the terminal cells, but any cell except for the most basal may produce zoospores.[ The zoospores have two flagella and up to 32 are produced per sporangial cell.]
Taxonomy
''Microthamnion'' was first described by Carl Nägeli
Carl Wilhelm von Nägeli (26 or 27 March 1817 – 10 May 1891) was a Swiss botanist. He studied cell division and pollination but became known as the man who discouraged Gregor Mendel from further work on genetics. He rejected natural selecti ...
in 1849 in Friedrich Traugott Kützing
Friedrich Traugott Kützing (8 December 1807 in Ritteburg – 9 September 1893) was a German pharmacist, botanist and phycologist.
Despite his limited background in regard to higher education, Kützing made significant scientific contribution ...
's work ''Species algarum''. It is recognized as a well-defined genus, but its placement has varied. Initially placed in the family Ulotrichaceae, at times, it has been placed in Trentepohliaceae
Trentepohliaceae are a family (biology), family of green algae, and the only family in the order Trentepohliales. It is a member of the Ulvophyceaen green algae. The family is characterized by traits like net-like chloroplasts without pyrenoids, ...
and Chaetophoraceae
Chaetophoraceae is a family (biology), family of green algae in the order Chaetophorales.
Members of the family are variously semi-terrestrial to aquatic in habitat, and consist of branched filaments in two parts, a prostrate system of filaments ...
until finally being placed in its own family. Currently, it is placed within its own family and order in the class Trebouxiophyceae
The Trebouxiophyceae, also known as trebouxiophytes, are a class of green algae, in the division Chlorophyta. Members of this class are single-celled, colonial, or multicellular and are found in freshwater, terrestrial or marine habitats worldwid ...
.[ As a consequence, opinions on the number of species vary widely, ranging from as few as one very polymorphic species][
]
References
Microthamniales
Trebouxiophyceae genera
Freshwater algae
{{green algae-stub