Paramoeba and Neoparamoeba

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


The genus Paramoeba Schaudinn, 1896, was described in 1896 by the German protistologist F. Schaudinn. The single species, P. eilhardi Schaudinn, 1896, appeared in saltwater aquaria in Berlin.

Grassi, in 1881, described two species of parasome-containing amoebae that are parasitic in chaetognaths. These two species were studied as species of Paramoeba by C. Janicki. However, Chatton (p. 44 in Grassé 1953) placed them in a new genus, Janickina Chatton in Grassé, 1953. The principal reasons for separating this genus from Paramoeba, according to Hollande (1980), are differences in the morphology of the amoeba during locomotion, and differences in the mode of nuclear division as seen under the light microscope. Hollande (1980) merged the two species of Janickina under the name J. pigmentifera (Grassi, 1881) Chatton in Grassé, 1953.

Additional species of Paramoeba Schaudinn:

These species are separated on the basis of cell size, the morphology of the locomotive amoebae, and the surface decoration of the cell (scales, glycostyles, or barren).

However, these criteria may not be meaningful. Molecular sequence data (forthcoming) are indicating that parasitic Neoparamoeba from lobsters, sea urchins and finfish all belong to a single clade, and should probably be best considered to be representatives of a single species. This species, if it includes the blue crab pathogen, would be called Neoparamoeba perniciosa (Sprague et al. 1969); P. pemaquidensis and P. invadens would be synonyms of N. perniciosa. At present, N. aestuarina appears to be a separate and distinct species ((Peglar et al. 2003 and forthcoming).

Page (1987) created the genus Neoparamoeba to separate species with hexagonal glycostyles (P. pemaquidensis, type of Neoparamoeba, and P. aestuarina) from P. eilhardi, which has scales on the cell surface. Moreover, the two genera were placed in different families (see the Classification section). Page (1987) did not consider parasitic species (which lack distinctive cell surface structures). Molecular data (Peglar et al. 2003 and forthcoming) indicate that Page (1987) was correct in separating the two genera but not in placing these genera in separate families. They also indicate that "species" lacking distinctive cell surface structures belong to Neoparamoeba and perhaps to one species of Neoparamoeba (N. perniciosa).

Modified (16 May 2003) provisional key to the species of parasome-containing amoebae

1. Locomotive form of amoeba with multiple digitiform pseudopods, often with subpseudopodia; free-living or, if parasitic, not in chaetognaths 2.
1. Locomotive form of amoeba with a single anterior lobose pseudopodium ("monopodial amoeba"); parasitic in chaetognaths, especially in the testicular region Janickina pigmentifera (Grassi)

2. Scales present on the cell surface; free-living, commonly feeding on eukaryotic algae; locomotive cells 35 - 75 micrometers in length Paramoeba eilhardi Schaudinn
2. No scales on the cell surface; free-living and bacterivorous, or parasitic; cells smaller Neoparamoeba; 3.

3. Hexagonal glycostyles present on the cell surface; sometimes fine hairs are also present 4.
3. Cell surface without obvious decoration, or state of cell surface unknown 5.

4. Locomotive cells usually 10-20 micrometres in length; usually one parasome per cell; free-living N. aestuarina (Page)
4. Locomotive cells usually 15-35 micrometres in length; up to five parasomes per cell; free-living or parasitic on finfish or shellfish N. pemaquidensis (Page)
(probably = N. perniciosa)

5. Cell surface barren; free-living or parasitic 6.
5. Cell surface structural details unknown; cell size comparable to P. pemaquidensis; free-living; Brazil (Rio de Janiero) P. schaudinni de Faria et al.
(Species inquirendae)

6. Apparently obligate parasite (no successful cultures to date); in crustacea, especially the blue crab Callinectes sapidus N. perniciosa (Sprague et al.)
6. Facultative parasite (will grow in culture, feeding on bacteria) in echinoderms (green sea urchins); Nova Scotia N. invadens (Jones)
(probably = N. perniciosa)

For information on the classification of Paramoeba, see the Classification page.

For lookalike taxa see Similar genera.

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

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