''Ulothrix'' 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 ...

in the family Ulotrichaceae. It is a common in

fresh Fresh may refer to: Arts, entertainment, and media Films and television * ''Fresh'' (1994 film), a crime film * ''Fresh'' (2009 film), a documentary film on sustainable agriculture * ''Fresh'' (2022 film), a thriller film *''Fresh with the Aust ...

to marine habitats, particularly colder and temperate waters. It has a

cosmopolitan distribution In biogeography, a cosmopolitan distribution is the range of a taxon that extends across most or all of the surface of the Earth, in appropriate habitats; most cosmopolitan species are known to be highly adaptable to a range of climatic and en ...

. The genus includes: * '' Ulothrix aequalis'' Guiry, M.D., John, D.M., Rindi, F and McCarthy, T.K. (ed.) 2007. ''New Survey of Clare Island Volume: The Freshwater and Terrestrial Algae''. Royal Irish Academy. . * ''Ulothrix moniliformis'' * '' Ulothrix flacca'' Burrows, E.M. 1991. ''Seaweeds of the British Isles Volume 2: Chlorophyta''. Natural History Museum, London . * '' Ulothrix implexa'' * '' Ulothrix speciosa'' * '' Ulothrix tenerrima'' * '' Ulothrix tenuissima'' * '' Ulothrix zonata''

Description

''Ulothrix'' consists of cells arranged end-to-end to form unbranched, uniseriate filaments. The filament is attached to a substrate via a basal cell, which may be rhizoidal. Cells are cylindrical or barrel-shaped; the apical cell may somewhat rounded at its terminal end. 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, ...

in young cells is thin and smooth, but becomes thick (and sometimes roughened) with age. Each cell has a single girdle-like and 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 ...

, which partially or fully circles the cell's circumference. The chloroplast contains a single

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 ...

which is surrounded by a starch envelope. Cells are uninucleate. Older cells may accumulate starch, oil or

volutin granules Volutin granules are an intracytoplasmic storage form of complexed inorganic polyphosphate, the production of which is used as one of the identifying criteria when attempting to isolate ''Corynebacterium diphtheriae'' on Löffler's medium. Polyphos ...

. The filaments may be surrounded by a layer of mucilage. Species of ''Ulothrix'' are identified based on the presence/absence of mucilage, the dimensions of cells, characteristics of the cell wall, and characteristics of the akinetes. The taxonomy of the genus is rather poorly known A similar genus is the poorly known '' Pearsoniella'', which differs in having completely closed (ring-shaped) chloroplasts, and sometimes having multiseriate filaments. It is a monotypic genus known from freshwater.

Reproduction

Vegetative reproduction in ''Ulothrix'' typically occurs via fragmentation, wherein the fragments develop into new filaments.Smith, G.M.1955 ''Cryptogamic Botany Algae and Fungi Volume 1 Second Edition'' McGraw-Hill Book Company Inc. Some of the vegetative cells of ''Ulothrix'' can occasionally develop into thick-walled

akinete An akinete is an enveloped, thick-walled, non-motile, dormant cell (biology), cell formed by both cyanobacteria and algae. Cyanobacterial akinetes are mainly formed by filamentous, heterocyst-forming members under the order Nostocales and Stigone ...

Asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the f ...

occurs via the formation of

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; zoospores are produced in multiples by vegetative cells, except for those with rhizoids. Zoospores are quadriflagellate (with four

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

) and have a cup-shaped chloroplast with a distinct stigma, and are positively

phototactic Phototaxis is a kind of taxis, or locomotory movement, that occurs when a whole organism moves towards or away from a stimulus (physiology), stimulus of light. This is advantageous for phototrophic organisms as they can orient themselves most e ...

Aplanospore {{Short pages monitor