Genus Trichamoeba Fromentel, 1874
Diagnosis: active locomotion form limax-like, regularly monopodial, slender to broad and thick, most between 75 and 250 µm in length; bulbous uroid or with short villi, some with fine filaments; floating form, where known, with radiating blunt pseudopodia; nucleus usually granular, with nucleoli arranged peripherally; commonly uninucleate; cytoplasm often with bipyramidal crystals.
Type species: Trichamoeba hirta (Fromentel, 1974)
Ecology: Freshwater and marine.
Remarks: These are the uninucleate, regularly monopodial, free-living Amoebidae. Other members of the family may occasionally become monopodial in rapid locomotion or under special conditions, and some such monopodial forms have pronounced uroids. It was to such a normally polypodial amoeba that Wallich gave the name Amoeba villosa. But Trichamoeba is always monopodial during steady locomotion in one direction, putting out another pseudopodium only for a marked change in direction (Page, 1988).
Trichamoeba may be confused with the more common Saccamoeba. With the light microscope these are most easily distinguished by the nucleus, which is ovular in all known species of Trichamoeba and has a single central nucleolus in known species of Saccamoeba. The floating form of most species of Trichamoeba has the pseudopodia characteristic of such forms in the Amoebidae, while that of Saccamoeba is irregularly rounded without pseudopodia (Page, 1988).
References: Bovee (1972); Schaeffer (1926); Siemensma & Page (1986).
Key to the species:
|1||Locomotive form usually > 150 µm||2|
|–||Locomotive form usually < 150 µm||T. cloaca|
|2||Amoeba slender, with a zigzag movement||T. sinuosa|
|–||Amoeba broad elliptical or ovoid||T. myakka|