Desmids are an order ( Desmidiales) in the Charophyta, a division of green algae that forms a sister group to the land plants ( Embryophyta). The Desmidiales comprise around 40 [1 ] genera and 5,000 to 6,000 [2 ] [3 ] species, found mostly but not exclusively in fresh water. Most are unicellular, the cell sometimes divided into two compartments separated by a narrow bridge or isthmus. Desmids assume a variety of highly symmetrical and generally attractive shapes, which provide the basis for their classification. Each compartment has one chloroplast, and no flagella. Sexual reproduction occurs through a process of conjugation, also found among the [4 ] Zygnematales. These two groups are closely related, and comprise the class Zygnematophyceae. The desmids are sometimes treated as members of the Zygnematales, [ but more often given the separate order Desmidiales. ] citation needed
Desmids possess characteristic
crystals of Barium sulphate at either end of the cell which exhibit a continuous [5 ] Brownian type motion.
References [ edit ]
^ Gontcharov AA, Marin BA, Melkonian MA (January 2003). "Molecular phylogeny of conjugating green algae (Zygnemophyceae, Streptophyta) inferred from SSU rDNA sequence comparisons". J. Mol. Evol. 56 (1): 89–104. doi: 10.1007/s00239-002-2383-4. PMID 12569426.
^ Van den Hoek, C., D. G. Mann, & H. M. Jahns, 1995. Algae:An Introduction to Phycology, page 468. (Cambridge: Cambridge University Press). ISBN 0-521-30419-9
^ Brook, Alan J., 1981. The Biology of Desmids, page 1. (Berkeley: University of California Press). ISBN 0-520-04281-6
^ 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 2802934. PMID 17272304.
^ Proceedings of the Royal Society -Biological Minerals Formed from Strontium and Barium Sulphates. II. Crystallography and Control of Mineral Morphology in Desmids
External links [ edit ]
Further reading [ edit ]
Survey of Clare Island 1990 - 2005, noting the Desmidiales recorded. Ed. 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