''Characium'' 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

Characiaceae Characiaceae is a family of green algae in the order Sphaeropleales. It contains epiphytic or planktonic algae that are unicellular or colonial. The cells are heteropolar, with basal and apical ends having different shapes. The daughter cells are ...

. It is very commonly found in freshwater habitats, where it is attached to

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater Aquatic ecosystem, ecosystems. The name comes from the Greek language, Greek words (), meaning 'plant', and (), mea ...

zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...

Description

''Characium'' consists of single or rarely clustered cells. They are attached to a plant or animal substrate (thus

epiphytic An epiphyte is a plant or plant-like organism that grows on the surface of another plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphyt ...

or epizoic), via a stalk or a circular pad. The cells have diverse shapes, ranging from fusiform to club-shaped or spherical, and are variously straight, hooked, or S-shaped. Cells usually contain a single 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 ...

filling 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 ...

. In some species, the chloroplasts fragment into multiple plastids, each with one pyrenoid. Mature cells have 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 ...

(are uninucleate). ''Characium'' reproduces asexually by

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 have two

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 ...

Identification

The genus ''Characium'' is similar to '' Characiopsis'', a type of algae in the class

Eustigmatophyceae Eustigmatophytes are a small group (17 genera; ~107 species) of eukaryotic forms of algae that includes marine, freshwater and soil-living species. All eustigmatophytes are unicellular, with coccoid cells and polysaccharide cell walls. Eus ...

. The two genera are very similar and have been confused in the past; however, ''Characium'' produces

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diet ...

to store excess carbon and thus stains brown to purple in

Lugol's iodine Lugol's iodine, also known as aqueous iodine and strong iodine solution, is a solution of potassium iodide with iodine in water. It is a medication and disinfectant used for a number of purposes. Taken by mouth it is used to treat thyrotoxic ...

solution, while ''Characiopsis'' does not. Many other similar segregate genera have been named. These include ''

Deuterocharacium ''Deuterocharacium'' is a genus of green algae in the family Characiaceae. It is found in freshwater habitats, attached to algae or detritus. It is rare and has only been recorded from Europe. Description ''Deuterocharacium'' consists of solitar ...

'', which differs in having chloroplasts without pyrenoids, and '' Characiopodium'', with multinucleate mature cells. Identification of species depends on the shapes and sizes of the cell body, as well as the stipe with which the body is attached.

Species list

* '' C. acuminatum'' * '' C. ambiguum'' * '' C. angustum'' * '' C. astipitatum'' * '' C. braunii'' * '' C. bulgariense'' * '' C. cerassiforme'' * '' C. conicum'' * '' C. epipyxis'' * '' C. giganteum'' * '' C. groenlandicum'' * '' C. guttula'' * '' C. heteromorphum'' * '' C. limneticum'' * '' C. marinum'' * '' C. nasutum'' * '' C. obtusum'' * '' C. ornithocephalum'' * '' C. ovale'' * '' C. polymorphum'' * '' C. prodani'' * '' C. pseudopyriforme'' * '' C. pyriforme'' * '' C. rostratum'' * '' C. saccatum'' * '' C. sieboldii'' * '' C. strictum'' * '' C. substrictum'' * '' C. subulatum'' * '' C. tenue'' * '' C. terrestre'' * '' C. urnigerum'' * '' C. westianum''

References

Sphaeropleales genera Sphaeropleales {{Chlorophyceae-stub