Locomotive form, subcylindrical

in cross-section

Acanthopodia

Amoebae of the genus Acanthamoeba produce slender, flexible, tapering subpseudopodia (which are called acanthopodia) from a broad, hyaline lobopodium (Page 1988). Acanthopodia contain an axial filamentous core (Bowers and Korn 1968) and can furcate (but never anastomose).

Cuticle

This is the term used by Page (1983, 1988) to  recognize the multilayered, stratified cell coat, like the one in Mayorella, Gocevia and Paragocevia. For more information on the classification of amoebae cell coats, see Smirnov and Brown (2004).

Dactylopodia

Short, finger shaped cytoplasmic projections that are produced by amoebae of the family Paramoebidae and, to some extent, Vexilliferidae. The term was introduced by Hollande (1945). For more information of the pseudopodial patterns see Page (1988), Smirnov and Goodkov (1999), and Smirnov and Brown (2004).

Double-walled cysts

Cysts of amoeboid protists may be single-walled or double-walled. Briefly, prior to encystment an amoeba stops feeding, decreases in cell volume by reducing the amount of water in the cytoplasm, rounds up and then secretes a cyst wall. Some species stop at this point - they have single-walled cysts. In other species the cell continues to reduce its volume and size and, after some time, secretes a second cyst wall, forming a double-walled cyst. At the sites of contact of the two cyst walls, cyst pores appear. The pore marks the place where an amoeba can destroy the cyst wall when it excysts.

Fan-shaped locomotive form

This is the locomotive form characteristic of the amoebae of the family Vannellidae. They are generally fan-shaped or semicircular when viewed from the top. A sample of these amoebae is illustrated in the figure. More terminology describing the shape of an amoeba may be found in Smirnov and Goodkov (1999).

Locomotive form, subcylindrical in cross-section

Normally we view an amoeba from the top, i.e. from the ventral surface. The cross-section of an amoeba can be examined using focusing of the microscope from the top to the bottom of the cell, by confocal technique, or just by observing amoebae moving on the surface of glass beads from the side. A variety of amoebae in cross-sections is illustrated in the figure. More on the terminology used to classify the cross-sections of the locomotive forms may be found in Page (1988) and Smirnov and Brown (2004).

Monoaxial flow of the cytoplasm

The cytoplasmic flow in an amoeba may be polyaxial or monoaxial. In the last case the cytoplasm forms numerous independent streams, while in the latter the single general axis of the cytoplasmic flow is oriented along the “core” of the pseudopod, as illustrated in the figure.

Monopodial locomotive form

It means that the amoeba forms a single pseudopodium in locomotion. Actually, the cell moves “as a whole” in this case. Monopodial amoebae may put out a lateral pseudopodium when changing direction (Page 1988). The terminology used to classify the locomotive forms may be found in Grebecki and Grebecka (1978) and Smirnov and Brown (2004).

MTOCs

MTOCs are MicroTubuli Organising Centers. In the strict sense of the word, they are a granular material, visible with electron microscope, from which microtubules arise and grow. Normally it is associated with centrioles, centriolar plaques, kinetosomes or some intracellular organelles (Margulis et al. 1993). In a broader sense, this term is usually applied to recognize all organelles like kinetosomes, centrioles and other structures that serve as centers of microtubule formation and growth.

Rolling movement of the cell membrane

In 1973, Haberey and Huelsmann demonstrated that during the locomotion of Vannella simplex the cell membrane rotates around the cell as a caterpillar. This type of movement seems to be characteristic for small, flattened, fan-shaped amoebae of the family Vannellidae, and for the smallest thecamoebids, like Thecamoeba orbis.

Scales

Some amoebae have scales on their surface. Scales are structures of complex shape, consisting (where studied) of polysaccharides with embeddings of calcium and other elements. Samples of scales may be found in Bark (1973), Page (1983, 1988), Smirnov (1999b), and Kudryavtsev (1999).