Vannellidae Family

The Vannellidae Family
Page updated 28/1/03
Clydonella	Platyamoeba		Lingulamoeba
Vannella

These 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 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. Further, an amoeba (Platyamoeba pseudovannellida) 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).
		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. A recent study (Peglar et al, 2003) indicated that Clydonella groups separately from either Vannella and Platyamoeba, but close to Lingulamoeba. Lingulamoeba resembles some species of Thecamoeba, indicating perhaps that Thecamoeba may be a sister group of Vannellidae, as inferred by Sawyer (Sawyer 1975) .
Related groups It is now apparent that the amoeba are polyphylectic, and thus not all amoeba are related but instead may be more closely to other protists such as ciliates. It appears that the Vannellidae family is related to the Paramoeba group (Peglar et al, 2003).
References:- 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. 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.