flabellate amoebae are among the most numerous genera found in water be it
freshwater, brackish or marine. These genera have been difficult
to distinguish morphologically at the light microscope level (especially
Clydonella vs Vannella) but have been
differentiated by the glycostyles, large glycoprotein complexes that
project from the cell surface (Figure 1), observed at the E.M. level.
Even classification by glycostyles is questioned by recent work that shows
that Clydonella has similar structures as Vannella !(Peglar
et al, 2003). However, recent SSUrDNA
analysis (Sims et
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. Further, an amoeba (Platyamoeba
that has an ability to exist in a wide range of salinities has
morphological features intermediate between Vannella and
Platyamoeba, but because of its glycocalyx has been placed in the
genus Platyamoeba (Hauer
et al, 2001). A second analysis (Peglar
et al, 2003)
with three Vannella species (V. aberdonica ATCC 50815, V.
anglica, and V. miroides ATCC 30945) and one Platyamoeba
(P. plurinucleolus ATCC 50745).
Hauer, G., Rogerson, A. & Anderson, O.
R. (2001) Platyamoeba pseudovannellida N.Sp., a naked amoeba with
wide salt tolerance isolated from the Salton sea, California. J. Euk.
Microbiol. 48, 663-669.
Peglar, M. T., Amaral Zettler, L. A.,
Anderson, O. R., Nerad, T. A., Gillevet, P. M., Mullen, T. E., Frasca Jr,
S., Silverman, J. D., O'Kelly, C. J. & Sogin, M. L. (2003) Two new
small-subunit ribosomal RNA gene lineages within the subclass
Gymnamoebia. J.Eukaryot.Microbiol. 50, 224-232.
(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
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.