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Name derivation: |
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From the Greek merismos –a division, and pedion –a plain, referring to the flat plate-like colonies of cells that divide regularly in one plane. |
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Classification: |
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Merismopedia Meyen 1839; 36 of 71 species descriptions are currently accepted taxonomically (Guiry and Guiry 2013).Order Synechococcales; Family Merismopediaceae Synonym AgmenellumBrébisson, 1839
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Morphology: |
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Spherical to oval cells densely arranged in rows forming flat and rectangular colonies in mucilage not extending outside a colony’s margins. No distinct sheath around individual cells. Identical base pair sequences of 16S rDNA in three described species (M. glauca, M. punctata and M. elegans) indicate that, while there is morphological variability in natural populations, the three species should be combined into a single description and name. Further, natural populations kept in culture changed to the point that based on their morphology they would be assigned to different species, or even genera (Palinska et al. 1996). The precautionary tale is that morphological plasticity and taxonomy based on it can be misleading, especially in the absence of base pair sequences.
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Similar genera: |
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Evidence of similarity of 16S rDNA sequences places Merismopedia and Synechocystis closely together with overall similarity of 95-97% (Ibid.). Classification scheme according to Bergey's manual of microbiology includes Merismopedia within the genus Gloeothece.
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Habitat: |
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Planktonic or benthic in both marine and fresh water. Some species occur in bogs. Merismopedia was the dominant photosynthetic plankter in acid Lake Njupfatet, Sweden, prior to whole-lake addition of calcite (liming). Nutrient enrichment experiments in enclosures in the lake stimulated Merismopedia (higher biomass) when NH4+ was added, but not when NO3- was added (Blomqvist et al. 1993). Later, whole lake liming caused Merismopedia to completely disappear (Blomqvist 1996). |
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References: |
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Blomqvist, P., R.T. Bell, H. Olofsson, U. Stensdotter and K. Vrede 1993. Pelagic ecosystem responses to nutrient additions in acidified and limed lakes in Sweden. AMBIO 22(5):283-289. Blomqvist, P. 1996. Late summer phytoplankton responses to experimental manipulations of nutrients and grazing in unlimed and limed Lake Njupfatet, central Sweden. Archiv für Hydrobiologie 137(4):425-455. Brébisson, A. de 1839. De quelques nouveaux genres d'algues. Mémoires de la Société Académique, Agricole, Industrielle et d'Instruction de l'Arrondissement de Falaise 1839: 34-37, pl with 3 figs. Graham L. E. and L. W. Wilcox 2000. Algae. Prentice Hall Guiry, M.D. and G.M. Guiry 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 04 September 2013. Jaeger, E. C. 1972. A source-book of biological names and terms. 3rd Ed. Charles C. Thomas Publisher Meyen, F.J.F. 1839. Neues system der pflanzen-physiologie. Dritter band. pp. i-x, 1-627, Plates X-XV. Berlin: Haude und Spenersche Buchandlung (S.J. Joseephy). Palinska, K.A., W. Liesack, E. Rhiel and W.E. Krumbein 1996. Phenotype variability of identical genotypes: the need for a combined approach in cyanobacterial taxonomy demonstrated on Merismopedia-like isolates. Archive of Microbiology 166:224-233. Wehr, J.D. and R. G. Sheath 2003. Freshwater Algae of North America. Academic Press (Imprint of Elsevier). |
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