Thecamoeba

Page updated 21/8/02

Thecamoeba at the Protist Information Server

Thecamoeba sp.

Freshwater pond Penciuk, S.E. Scotland.  Amoeba moving towards the bottom left, prominent contractile vacuole towards rear.  Bar=20um.

Figure 1.

Figure 2.

The amoeba on the left is a very large Thecamoeba isolated from moss.  This particular amoeba had the appearance of vacuum packed mince with an ill fitting hyaline coat. It seemed to be feeding on unicellular algae.

The glycocalyx is thick but not organised into discrete units as Vannella. Thecamoeba from terrestrial and freshwater tend to be large amoebae generally being more than 50mm in length, whereas so far, those from seawater have tended to be smaller (Page & Blakey, 1979), but this might be because one particular small Thecamoeba (T. orbis) is very common (Page 1983; Rogerson & Gwaltney, 2000).  There have been many named species but for the majority of these the validity is not certain.  The genus Sappinia is similar to Thecamoeba but it tends to be bi-nucleate and is supposedly sexual. As far as I know, no genetic information is known for any member of the genus.  This will be hampered by the fact that many Thecamoeba feed on other protists including other amoebae (the presence of other eukayotes is a problem as PCR using the usual primers may amplify the SSUrDNA organisms other than the Thecamoeba under study). The contractile vacuole has been suggested as a tool for differentiating Thecamoeba (see T. quadrilineata below), from Nuclearia and Mayorella (Patterson, 1981), however some (e.g. T. orbis) do not have contractile vacuoles.  Attempts have been made to differentiate members of the genus by nuclear structure and division patterns (Singh et al, 1981).  These studies lead to the suggestion that the genus could be split between those that had a Feulgen-negative nucleoli or nucleolus giving rise to polar masses with the nuclear membrane remaining - this is known as promitosis, the other group Feulgen-negative nucleoli or nucleolus and the membrane disappear and a spindle forms organising chromosomes as in animals and plants.  The exact details of cell division in the amoeba and protist in general are difficult as these organisms tend not to have much DNA and a high level of other material that stains with DNA intercalating agents both chromatic and fluorescent (See Specific Stains for the Amoebae).  

T. hilla  32-68mm in length (x 50mm) (Page, 1983). A single central nucleolus. Marine, oblong with visible longitudinal folds.  Estimates (Page, 1983), put the length between 11-25mm with some very large individuals at 30mm, while another put the average figure at 19.5mm (Rogerson, 1991).  However, Smirnov (Smirnov, 1999) found a Baltic strain that was between 9-12mm, within the range of the isolate shown. T. orbis feeds on flagella and bacteria (Schaeffer, 1926).  Nucleus 3-6mm in diameter with a single nucleolus (Page, 1983). No floating form has been commented upon.

T. orbis 11-25mm in length (x 16mm) (Page, 1983; Page & Blakey, 1979). Marine, looks like flabellate amoebae but with longitudinal folds. The form in locomotion is oval or circular with the anterior half, a hyaline flattened area, and the posterior granulated half containing the nucleus thicker. The longitudinal folds extend from the rear towards the leading edge, but usually not quite at the edge. These folds usually number between 2 and 5 and appear to be quite stable.  From North sea (Europe), Baltic (Smirnov, 1999), W.N. Atlantic, Indian ocean and Gulf of Mexico it is the most common marine Thecamoeba according to Page (Page, 1983). The size of T. orbis is variable, the specimen in figure 3 was isolated from a supra-littoral rock-pool at Yellowcraigs, S.E. Scotland, and at 11mm in length is slightly smaller than a typical T.orbis. Schaeffer (Schaeffer, 1926), reported a length between 20-30mm, other estimates (Page, 1983), put the length between 11-25mm with some very large individuals at 30mm, while another put the average figure at 19.5mm (Rogerson, 1991). 

Figure 3

Thecamoeba orbis bar =10mm. Cell moving towards the upper right.

      However, Smirnov (Smirnov, 1999) found a Baltic strain that was between 9-12mm, within the range of the isolate shown. T. orbis feeds on flagella and bacteria (Schaeffer, 1926).  Nucleus 3-6mm in diameter with a single nucleolus (Page, 1983). No floating form has been commented upon. The nucleus of  T. orbis is often not visible in the living amoebae.

T. quadrilineata 35-100mm in length (x 50mm), a tendency for very large forms in culture.  Not very wrinkled in appearance.  Floating forms with banana like pseudopods. A single prominent contractile vacuole often seen.  The behaviour of the contractile vacuole of T. quadrilineata (CCAP1583/7) has been studied in detail (Patterson, 1981). Nucleus with single central nucleolus.

T. similis 30-80mm in length (x 50mm) Broader than most Thecamoeba.

T. sphaeronucleolus 80-130mm in length (x 100mm) Nucleolus often in 2 or 3 parts.

T. striata 30-80mm in length (x 50mm) Very similar in appearance to T. quadrilineata but no large forms and difference in nuclear structure. (Page, 1988). Nucleus is elliptical with parietal lobes.

T. terricola 60-200mm in length (x 110mm) (Page, 1988).Oblong like T. verrucosa with an oblong nucleus, with multi-lobed nucleolus often parietal.

T. verrucosa 80-130mm in length (x 100mm) (Page, 1988).Oblong, but baggy appearance with a defined uroid gathered and contracted as in T. terricola. 

Bovee, E.C. (1960). "Studies on feeding behaviour of amebas. 1. Ingestion of thecate rhizopods and flagellates by verrucosid amebas, particularly Thecamoeba sphaeronucleolus. J.Protozool., 7: 55-60.

Page, F.C. (1971). "A comparative study of five freshwater and marine species of Thecamoebidae." Trans.Am.Microsc.Soc. 90: 157-173.

Page, F.C. (1977). "The genus Thecamoeba (Protozoa, Gymnamoebia): Species distinction, locomotive morphology and protozoan prey." J.Nat.Hist., 11: 25-63.

Page, F.C. & Blakey, S.M. (1979). "Cell surface structure as a taxonomic character in the Thecamoebidae (Protozoa: Gymnamoebia). Zool. J. Linn. Soc. 66: 113-135.

Page, F.C. (1983). "Marine gymnamoebae" Inst.Terr.Ecol. NERC, Cambridge, England.

Patterson, D.J. (1981). "Contractile vacuole complex behaviour as a diagnostic character for free-living amoebae." Protistologica 17, 243-248.

Rogerson, A. (1991). "On the abundance of marine naked amoebae on the surface of five species of macroalgae." FEMS Microbiol.Ecol. 85, 301-312.

Rogerson, A. & Gwaltney, C. (2000). "High numbers of naked amoebae in the planktonic waters of a mangrove stand in Southern Florida." J.Euk.Microbiol. 47(3): 235-241.

Sawyer, T.K. (1975). "Marine amoebae from the surface waters of the Chincoteaque Bay, Virginia: one new genus and eleven new species within the families Thecamoebidae and Hyalodiscidae." Trans.Amer.Microscop.Soc. 94: 395-400.

Singh, B.N., Mistra, R., & Sharma, A.K. (1982a). "Nuclear structure and nuclear division as the basis for the subdivision of the genus Thecamoeba Fromental, 1874." Protistologica 17(4): 449-464.

Singh, B.N. & Hanumaiah, V. (1979). Studies on pathogenic and non-pathogenic amoebae and the bearing of nuclear division and locomotive form and behaviour on the classification of the order Amoebida.  Mongraph No. 1.  Association of Microbiologists of India.  Ind.J.Microbiol. 1-80.

Smirnov, A.V. (1999). "An illustrated survey of gymnamoebae isolated from anaerobic sediments of the Niva bay (The Sound)." Ophelia 50(2), 113-148.