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Characeae

Characeae
Chara globularis
Scientific classification Edit this classification
Clade: Viridiplantae
(unranked): Charophyta
Class: Charophyceae
Order: Charales
Family: Characeae
S.F.Gray
Genera

See text.

Characeae is a family of freshwater green algae in the order Charales, 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 is followed here. In other treatments, the genus Nitellopsis, which has both extant and extinct species, is placed in a separate family, Feistiellaceae.

Nitellopsis obtusa
Submerged meadow of Chara vulgaris

Description

Living members of the Characeae sensu lato grow in freshwater and brackish environments worldwide, and have large, macroscopic thalli growing up to 120 cm long, they are branched, multicellular, and use chlorophyll to photosynthesize. Their only diploid stage in the life cycle is the unicellular oospore. They may be called stoneworts,[1] 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. In these whorls it is possible to see the phenomenon of cytoplasmic streaming. 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 to stop streaming.[citation needed]

There are about 400 extant species worldwide, with 33 in Britain and Ireland according to Groves and Bullock-Webster),[2][3] however Stewart and Church (1992) reduce this to 21.[4]

Characeae are the principal photosynthesizers of some of the volcanic crater lakes of Nicaragua, and can be found in excess of 20 meters depth in some circumstances. Introduced tilapia (Oreochromis niloticus) consumed all the Characeae in Lake Apoyo.[5]

The antheridia (or globules[6]) and oogonia (or nucules[6]) 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:[7]

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.[9] They are usually found in low to medium nutrient-rich water and tend to disappear due to eutrophication. Some stoneworts can survive in brackish or maritime habitats and occur in ephemeral saline lakes in Australia that have twice the salinity of seawater.[10]

References

  1. ^ Kapraun, D.F. (2007), "Nuclear DNA content estimates in green algal lineages: chlorophyta and streptophyta", Ann. Bot., 99 (4): 677–701, doi:10.1093/aob/mcl294, PMC 2802934, PMID 17272304
  2. ^ Groves, J. & Bullock-Webster, G.R. (1920), The British Charophyta. Vol. 1, Nitelleae, London: The Ray Society, OCLC 504031618
  3. ^ Groves, J. & Bullock-Webster, G.R. (1924), The British Charophyta. Vol.2, Chareae, London: The Ray Society, OCLC 928852232
  4. ^ Stewart, N.F. & Church, J.M. (1992), Red Data Books of Britain and Ireland, Peterborough: The Joint Nature Conservation Committee, ISBN 978-1-873701-24-9
  5. ^ McCrary, J.K.; Murphy, B.R.; Stauffer Jr., J.R. & Hendrix, S.S. (2007), "Tilapia (Teleostei: Cichlidae) status in Nicaraguan natural waters" (PDF), Env. Biol. Fishes, 78 (2): 107–114, doi:10.1007/s10641-006-9080-x, S2CID 23302504, archived from the original (PDF) on 2011-10-03, retrieved 2011-05-31
  6. ^ a b "Structure and Reproduction in Chara - Fresh Water Green Algae", Botany Studies, 6 August 2017, retrieved 2019-09-03
  7. ^ "Characeae Agardh", Interim Register of Marine and Nonmarine Genera (IRMNG), retrieved 2022-02-20
  8. ^ Guiry, M.D.; Guiry, G.M., "Nitellopsis", AlgaeBase, World-wide electronic publication, National University of Ireland, Galway, retrieved 2022-02-20
  9. ^ John, D.M.; Whitton, B.A. & Brook, A.J. (2002), The Freshwater Algal Flora of the British Isles, London: Cambridge University Press, ISBN 978-0-521-77051-4
  10. ^ Burne, R.V.; Bauld, J. & de Decker, P. (1980), "Saline lake charophytes and their geological significance", Journal of Sedimentary Petrology, 50: 281–293, doi:10.1306/212F79D2-2B24-11D7-8648000102C1865D
Quelle: https://en.wikipedia.org/wiki/Characeae