Charales

Stoneworts
Chara globularis
Scientific classification
Kingdom: Plantae
Division: Charophyta
Class: Charophyceae
Order: Charales
Family: Characeae
Genera

Chara
Lamprothamnium
Lycnothamnus
Nitella
Nitellopsis
Tolypella

Charales is an order of freshwater green algae in the division Charophyta, class Charophyceae, commonly known as "stoneworts". Linnaeus established the genus Chara in 1753.

Description

The Charales have large, macroscopic thalli growing up to 120 cm long, they are branched, multicellular, and use chlorophyll to photosynthesize. They grow in fresh water. 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, this gives them a superficial resemblance to the genus Equisetum. In these whorls it is possible to see the phenomenon of cytoplasmic streaming. In fact the 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.

There are about 400 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 plant life 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]

Species

Submerse meadow of Chara vulgaris
Limy crust on Chara spec. in a spring pond

British Isles

Ref: Stewart & Church (1992).[4]

Other regions

Distribution

Ireland

Ecology

Most 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.[10] 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.[11]

Life history

The antheridia and oogonia 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 Charales have the most complex structure of all green algae, if indeed they should be so labelled.

The possible sister group of the land plants are also known as brittleworts or skunkweed. These curious labels arise from the fragility of their lime-encrusted stems, and from the foul odor these produce when stepped on.

Many botanists propose that the stoneworts and their relatives be placed in a division, sub-kingdom, or even kingdom by themselves, often named Charophyta. Their classification by taxonomists is currently undergoing much cladistic scrutiny. Further DNA and RNA analysis may prove the charophytes to be a crucial evolutionary link in the phylogenetic tree of life, the critical developmental step from the algae toward the non-vascular and then vascular land plants.

References

  1. ↑ Kapraun DF (April 2007). "Nuclear DNA content estimates in green algal lineages: chlorophyta and streptophyta". Ann. Bot. 99 (4): 677–701. doi:10.1093/aob/mcl294. PMC 2802934Freely accessible. PMID 17272304.
  2. ↑ Groves, J. and Bullock-Webster, G.R. 1920. The British Charophyta. Vol.1, Nitelleae. London, The Ray Society
  3. ↑ Groves, J. and Bullock-Webster, G.R. 1924. The British Charophyta. Vol.2, Characeae.. London, The Ray Society
  4. 1 2 Stewart, N.F. and Church, J.M. 1992. Red Data Books of Britain and Ireland. The Joint Nature Conservation Committee, Peterborough. ISBN 1-873701-24-1
  5. ↑ McCrary JK, Murphy BR, Stauffer, Jr. JR, Hendrix SS (2007): Tilapia (Teleostei: Cichlidae) status in Nicaraguan natural waters; Env. Biol. Fishes 78:107-114
  6. ↑ ITIS Standard Report Page: Chaetosphaeridiaceae
  7. ↑ Algaebase :: Species Detail
  8. 1 2 3 Morton, O. 1992 in Hackney, P. (Ed.) Stewart & Corry's Flora of the North-east of Ireland. Institute of Irish Studies and The Queen's University of Belfast ISBN 0-85389-446-9 (HB)
  9. ↑ Guiry, M.D., John, D.M., Rindi, F. and McCarthy, T.K 2007. New Survey of Clare Island, Volume 6: The Freshwater and Terrestrial Algae. Royal Irish Academy. ISBN 978-1-904890-31-7
  10. ↑ John, D.M., Whitton, B.A. and Brook, A.J. 2002. The Freshwater Algal Flora of the British Isles. Cambridge University Press, London. ISBN 0-521-77051-3
  11. ↑ Burne, R.V., Bauld, J. and de Decker, P. 1980. Saline lake charophytes and their geological significance. Journal of Sedimentary Petrology, 50, 281-293. As quoted by: Purbeck Formation - Jurassic-Cretaceous. Lithology, fauna, facies and palaeoenvironments. Geology of the Dorset Coast. Ian West, Romsey, Hampshire and School of Ocean and Earth Science, National Oceanography Centre, Southampton University, Southampton. 2009. http://www.southampton.ac.uk/~imw/purbfac.htm accessed 5 August 2013

Further reading

Further links

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