Adhesion, Morphology, and Locomotion of Paramoeba pemaquidensis Page (Amoebida, Paramoebidae): Effects of Substrate Charge Density and External Cations1

Morphology and locomotive behavior in the marine amoeba, Paramoeba pemaquidensis Page, was examined under different environmental conditions. Paramoeba requires a minimum surface negative charge density for adhesion of amoebae to substrata. Once adhesion to the substratum has been attained, however, surface negative charge density has no effect on morphology or locomotive rate. Divalent cations are not required for adhesion, but external calcium is required for normal locomotion. In the presence of calcium, Paramoeba often assumes a locomotive form with a broad, well‐developed anterior hyaline region and truncate posterior region. Locomotive forms vary from those with only a well‐developed hyaline region (Flabellula‐like) to forms with long digitiform sub‐pseudopodia (Vexillifera‐like), with intermediate morphotypes. Locomotive rates decrease and anteroposterior polarity disappears in the presence of living or heat‐killed bacteria, indicating that phagocytosis temporarily interferes with locomotion and alters form.