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Vannella vs Platyamoeba

Page updated 28/1/03

These flabellate amoebae are among the most numerous genera found in water be it freshwater, brackish or marine. These genera have been very difficult to distinguish morphologically at the light microscope level and can be differentiated by the glycostyles, large glycoprotein complexes that project from the cell surface (Figure 1).  However, recent SSUrDNA analysis (Sims et al, 2002) reveals that Vannella and Platyamoeba are closely related and in fact sort out on the basis of the environment from which they have been isolated so that Vannella and Platyamoeba from seawater group together and are distinct from the group of amoebae previously identified as either Vannella and Platyamoeba on morphological basis.  
Figure 1
There is a wider debate concerning the relative merits of morphological versus SSUrDNA as suitable markers of phylogeny, and it should be remembered that this analysis involved only a ~380bp fragment of the SSUrDNA gene (Sims et al, 2002).  Perhaps what is required is an additional data set on a second, unrelated gene such as (perhaps EF-1a, used successfully for a number of other groups).
This finding leaves the question of Clydonella even more uncertain (Sawyer et al, 1975), as this genera has feature reported to be intermediate between Vannella and Platyamoeba.
 

References:-

Sawyer, T.K. (1975c). "Clydonella n.g. (Amoebida: Thecamoebidae) proposed to provide an appropriate generic home for Schaeffer's marine species of  Rugipes, C. viva (Schaeffer, 1926) n. comb. Trans Am.Microscop.Soc. 94:395-400.

Sims, G. P., Aitken, R. & Rogerson, A. (2002) Identification and phylogenetic analysis of morphologically similar naked amoebae using small subunits ribosomal RNA. J.Eukaryot.Microbiol. 49, 478-484.

 
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