Paramoeba
Index | Introduction | Appearance | Ultrastructure | Reproduction and Life History | Similar genera | Classification | Taxonomy and Nomenclature | Cultures | References | Internet resources

ULTRASTRUCTURE
Entities that have been assigned to five of the six species of Paramoeba have been examined with the electron microscope. No information is available for specimens assigned to P. schaudinni de Faria et al. The original description of this species is vague, and it may never to be possible to know for sure whether an amoeba in hand is the same one that de Faria and colleagues studied. Moreover, the "species" assigned on the basis of morphology and ultrastructure may or may not accurately reflect the situation in nature (more on this topic in the Taxonomy and nomenclature section).
CELL SURFACE. The species are not all alike. The type species, P. eilhardi, has a single layer of scales that covers the entire cell surface. The scales are made of organic materials, without any sign of mineralization (they do not contain carbonates or silicates). Each scale has an ellipsoidal base that adheres to the cell surface. From this base, several vertical elements ("columns") arise that support a simple rim. There are usually eight, but may be as many as fourteen, columns. The scales are formed in the Golgi apparatus.

The two species P. pemaquidensis and P. aestuarina have a surface coat that consists of tiny discrete bodies termed "glycostyles". The glycostyles are organic (not mineralized), cover the entire cell surface, and appear to be formed in the Golgi. They may sometimes appear to be hexagonal in outline, and are seldom taller than broad. Some but not all strains of P. pemaquidensis and P. aestuarina also have hairlike filaments that arise from the cell membrane.
No surface coat has been found in the parasitic species P. invadens and P. perniciosa.

PARASOME. The parasome is bounded by two membranes. Within these membranes there are three distinct structures that are also bounded by two membranes: two peripheral bodies and one central body. These are the structures within the parasome that show the positive reaction to DNA-binding dyes and fluorochromes. There is a limited amount of cytoplasm within the parasome that is not contained within either the peripheral or the central bodies.
OTHER ORGANELLES. As far as is known, all species of Paramoeba have one nucleus per cell. The nucleus has a single, centrally located, essentially spherical nucleolus.

Each cell has several sausage-shaped, unbranched mitochondria. The cristae are tubular.

The finger-like pseudopodia ("dactylopodia") may have a central core of fine fibrils. Such fibrils are not commonly observed in other amoebae. The composition and function of these fibrils is not known.

Some species, P. eilhardi especially, harbor endosymbiotic bacteria.

Paramoeba:   Index | Introduction | Appearance | Ultrastructure | Reproduction and Life History | Similar genera | Classification | Taxonomy and Nomenclature | Cultures | References | Internet resources

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