Characeae is a

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

of freshwater

green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...

in the order

Charales Charales is an order of freshwater green algae in the division Charophyta, class Charophyceae, commonly known as stoneworts. Depending on the treatment of the genus '' Nitellopsis'', living (extant) species are placed into either one family (Ch ...

, commonly known as stoneworts. They are also known as brittleworts or skunkweed, from the fragility of their lime-encrusted stems, and from the foul odor these produce when stepped on. In some treatments, the Characeae includes all the living (extant) species of Charales; this

circumscription Circumscription may refer to: *Circumscribed circle *Circumscription (logic) *Circumscription (taxonomy) * Circumscription theory, a theory about the origins of the political state in the history of human evolution proposed by the American anthrop ...

is followed here. In other treatments, the genus ''

Nitellopsis ''Nitellopsis'' is a genus of Charophyta, charophyte green algae. Some sources, including AlgaeBase, place it in the family Feistiellaceae. Others place it in the family Characeae. Species , AlgaeBase listed the following species: ;Extant *''Nite ...

'', which has both extant and extinct species, is placed in a separate family, Feistiellaceae. Nitellopsis obtusa

Description

Living members of the Characeae ''

sensu lato ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...

'' grow 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. Although the term specifically excludes seawater and brackish water, it does include ...

and

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

environments worldwide, and have large, macroscopic

thalli Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms were ...

growing up to 120 cm long, they are branched,

multicellular A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism. All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- ...

, and use

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...

photosynthesize Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...

. Their only

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

stage in the life cycle is the unicellular

oospore An oospore is a thick-walled sexual spore that develops from a fertilized oosphere in some algae, fungi, and oomycetes. They are believed to have evolved either through the fusion of two species or the chemically-induced stimulation of mycelia, ...

. They may be called ''stoneworts'', because the plants can become encrusted in lime ( calcium carbonate) after some time. The "stem" is actually a central stalk consisting of giant, multinucleated cells. They are unique in having a whorl of small branchlets at each node in the stipe which gives them a superficial resemblance to the genus ''

Equisetum ''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of ferns, which reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass Eq ...

''. In these whorls it is possible to see the phenomenon of

cytoplasmic streaming Cytoplasmic streaming, also called protoplasmic streaming and cyclosis, is the flow of the cytoplasm inside the cell, driven by forces from the cytoskeleton. It is likely that its function is, at least in part, to speed up the transport of mol ...

. Streaming in ''Chara'' is the fastest recorded of any cell. Cytoplasmic streaming is caused by the microfilaments found inside the cell, as proven by the use of

cytochalasin B Cytochalasin B, the name of which comes from the Greek ''cytos'' (cell) and ''chalasis'' (relaxation), is a cell-permeable mycotoxin. It was found that substoichimetric concentrations of cytochalasin B (CB) strongly inhibit network formation by act ...

to stop streaming. There are about 400 extant

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

worldwide, with 33 in

Britain Britain most often refers to: * The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands * Great Britain, the largest island in the United King ...

and

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

according to Groves and Bullock-Webster), however Stewart and Church (1992) reduce this to 21. Characeae are the principal photosynthesizers of some of the volcanic crater lakes of

Nicaragua Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the cou ...

, and can be found in excess of 20 meters depth in some circumstances. Introduced

tilapia Tilapia ( ) is the common name for nearly a hundred species of cichlid fish from the coelotilapine, coptodonine, heterotilapine, oreochromine, pelmatolapiine, and tilapiine tribes (formerly all were "Tilapiini"), with the economically most ...

(''Oreochromis niloticus'') consumed all the Characeae in Lake Apoyo. The

antheridia An antheridium is a haploid structure or organ producing and containing male gametes (called ''antherozoids'' or sperm). The plural form is antheridia, and a structure containing one or more antheridia is called an androecium. Androecium is also ...

(or globules) and

oogonia An oogonium (plural oogonia) is a small diploid cell which, upon maturation, forms a primordial follicle in a female fetus or the female (haploid or diploid) gametangium of certain thallophytes. In the mammalian fetus Oogonia are formed in lar ...

(or nucules) are protected by a layer of sterile cells when mature; the oogonium is oblong in shape and consists of a single egg, while the spherical antheridium is packed with threadlike cells that produce spermatia. As a result, the Characeae have the most complex structure of all green algae.

Genera

Genera that include extant species and are placed in a broad circumscription of the family are: *'' Chara'' L. *'' Lamprothamnium'' J.Groves *'' Lychnothamnus'' (F.J.Ruprecht) A.Braun *''

Nitella ''Nitella'' is a genus of charophyte green algae in the family Characeae. Species The species in the genus include: *'' Nitella abyssinica'' A. Braun * '' Nitella acuminata'' A. Braun ex Wallman *'' Nitella aemula'' A. Braun * '' Nitella an ...

'' C.A.Agardh *''

'' Hy (placed in Feistiellaceae by some sources) *'' Tolypella'' (A.Braun) A.Braun

Ecology

Most extant Characeae are found in fresh water, usually in still, clear water where they attach to the substrate by rhizoids. They can be pioneer colonizers or ephemerals. They are usually found in low to medium nutrient-rich water and tend to disappear due to

eutrophication Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...

. Some stoneworts can survive in brackish or maritime habitats and occur in ephemeral saline lakes in Australia that have twice the salinity of seawater.

References

{{taxonbar, from1=Q1559048 Charophyta Green algae families