Microworld

world of amoeboid organisms

Menu
Pelomyxa palustris
Pelomyxa palustris

Genus Pelomyxa Greeff, 1874

Diagnosis: Free-living amoebae from anaerobic or micro-aerophilic habitats, cells amoeboid, reaching 5 mm long with a large anterior pseudopod and a posterior uroid; shell usually spherical to elongated ovoid; one to numerous nuclei; short flagella present in most species; cytoplasm filled contains several glycogen bodies; different types of symbiotic bacteria have been observed; all pelobionts lack mitochondria.

Remarks: Pelobionts are an original group of amoeboid protists inhabiting bottom sediments of freshwater basins under micro aerobic or anaerobic conditions. Earlier investigators described nearly twenty species. Later, the validity of most species was doubted and studies of Chapman-Andresen, (1978, 1982) showed a complex life cycle, and all Pelomyxa species ever described, were considered to be stages of the life cycle of Pelomyxa palustris. This led to the conclusion that Pelomyxa palustris was a polymorphic species.
Since 2004, a series of studies by Frolov et al (2004, 2005, 2006, 2011) changed this view completely. They provided evidence that some original described species are valid species and no part of a complex life cycle of Pelomyxa palustris. Concerning the latter, it is still unclear whether P. palustris is a nominal species or a group of species erroneously united into a single taxon.

Pelomyxa representatives are multinuclear and possess numerous immobile flagella. All pelobionts lack mitochondria and most, with the exception of Mastig­amoeba punctachora and P. palustris, the Golgi apparatus.

Key to Pelomyxa species:

1 Usually with two nuclei 2
Usually with more than two nuclei 3
2 Nuclei < 30 µm P. flava
Nuclei > 30 µm P. binucleata
3 Cell with numerous conical projections P. corona
Cell without such projections 4
4 Nucleus with central nucleolus 5
Nucleus with small peripheral nucleoli P. palustris
5 No glycogen bodies present P. gruberi
Glycogen bodies present P. stagnalis
Immobile cilia
Recent posts

Nebela golemanskyi

N. golemanskyi, after Todorov, 2010 Nebela golemanskyi Todorov, 2010 Diagnosis: Shell large, colourless and pyriform, with a distinct short neck about one fourth of the

Read More »

Nebela nebeloides

N. nebeloides, after Gauthier-Lièvre and Thomas, 1958 Nebela nebeloides (Gauthier-Lièvre and Thomas, 1958) Todorov et al., 2010 Basionym: Difflugia nebeloides Gauthier-Lièvre and Thomas, 1958 Diagnosis:

Read More »

Difflugia biwae

D. biwae, after Yang and Shen, 2005 Difflugia biwae Kawamura, 1918 Diagnosis: Shell in lateral view fusiform in outline with a straight neck, a conspicuous

Read More »

Difflugia mulanensis

D. mulanensis, after Yang et al., 2015 Difflugia mulanensis Yang, Meisterfeld, Zhang and Shen, 2015 Diagnosis: Shell elongate ovoid like a vase, with a distinct

Read More »

Euglypha bryophila

Euglypha bryophila, after Brown, 1911 (L), from Ecuador (R) Euglypha bryophila  Brown, 1911 Diagnosis: (Original description) The test is very regular in form and subject

Read More »

Vernalophrys

(A) A Scenedesmus cell (arrow) is engulfed by a trophozoite. (B) Several Scenedesmus cells adhere to the surface of a plasmodium that has numerous vacuoles

Read More »