Genus Trichamoeba Fromentel, 1874

Diagnosis: Locomotive form limax‑like, regularly monopodial, slender to broad and thick, usually 75–250 µm long. Uroid bulbous or bearing short villi, occasionally with fine filaments. Floating form, where known, with radiating blunt pseudopodia. Nucleus typically granular, with nucleoli arranged peripherally; commonly uninucleate. Cytoplasm often contains bipyramidal crystals.

Type species: Trichamoeba hirta (Fromentel, 1974)

Ecology: Freshwater and marine.

Remarks: These are uninucleate, regularly monopodial, free‑living Amoebidae. Other members of the family may occasionally become monopodial during rapid locomotion or under special conditions, and some such monopodial forms possess pronounced uroids. It was to such a normally polypodial amoeba that Wallich gave the name Amoeba villosa. In contrast, Trichamoeba is consistently monopodial during steady locomotion in one direction, producing an additional pseudopodium only when making a marked change in direction (Page, 1988).

Trichamoeba may be confused with the more common Saccamoeba. Under the light microscope, the two are most easily distinguished by the nucleus: in all known species of Trichamoeba it is ovular with peripheral nucleoli, whereas in Saccamoeba it is ovular with a single central nucleolus. The floating form of most Trichamoeba species has the radiating pseudopodia typical of floating forms in the Amoebidae, while that of Saccamoeba is irregularly rounded and lacks pseudopodia (Page, 1988).

References: Bovee (1972); Schaeffer (1926); Siemensma & Page (1986).

Key to the species: