Flabellula Bovee, 1965 (ref. ID; 2298) or Schaeffer, 1926 (ref. ID; 3687, 7710)

[ref. ID; 7710]
Type species; Flabellula citata Schaeffer, 1926 (ref. ID; 7710)

  1. Flabellula calkinsi (Hogue, 1914) Schaeffer, 1926 (ref. ID; 2298)
  2. Flabellula citata Schaeffer, 1926 (ref. ID; 2298, 3687, 7710)
  3. Flabellula hoguae Sawyer, 1975 (ref. ID; 7710)
  4. Flabellula mira Schaeffer, 1926 (ref. ID; 3687)
  5. Flabellula pellucida Schaeffer, 1926 (ref. ID; 3687)

Flabellula calkinsi (Hogue, 1914) Schaeffer, 1926 (ref. ID; 2298)


While these amoebae in their broadened locomotive form were often somewhat fan-shaped or spatulate, the fan-like form was usually more irregular than that of F. citata. The hyaline zone often took up more than 1/3 the length. When such broadened cells changed direction, the rift formed in the hyaline zone was not so deep and regular as in F. citata, and this species did no usually produce long, conical pseudopods in that way. Change of direction sometimes occurred by a balling up of the cell followed by protrusion of a new hyaline zone. A more limax-like locomotive form was often produced when one part of the hyaline zone advanced more rapidly than the rest. Such as elongated form was not as cylindrical as that of a true limax amoebae but resembled more the limax-like form produced by Platyamoeba stenopodia. If such as elongated amoebae changed direction by expansion of its hyaline zone in the new direction, a broadened form was produced, at least temporarily. More often, the limax-like form changed to the broad one by bilateral expansion of the hyaline zone accompanied by a drawing forward of the granular region. Many amoebae of this species lacked uroidal filaments at any given time, but such filaments occasionally occurred on the broadened forms. Feeding occurred by invagination of the anterior edge of the hyaline zone when it came into contact with a bacterium. The cytoplasm behind the hyaline zone was not as densely granular as in F. citata. Phase-contrast observations of flattened living cells showed that it contained granules measuring approximately 0.3-0.5 um; some rod-shaped bodies approximately 1.5 um long; often some rather dense spherules (1-1.5 um); often several apparently clear vesicles; and small food vacuoles containing bacteria. In addition, there might be 1-4 larger spheres of various sizes in vacuoles. The nuclear, usually in the anterior part of the granular region, contained a central nucleolus with a diameter 1/2 that of the nucleus or less. Interphace nuclei were entirely Feulgen-negative. Multinucleate amoebae were common. Of 500 cells tallied on a Kernechtrot preparation, 59 (approximately 12%) were binucleate, and 2 were trinucleate. Apart from the 500 cells thus tallied, one amoeba with 4 nuclei and one with 5 nuclei were recorded. Generally amoebae with more than one nucleus were larger than uninucleate amoebae. Also larger cells seemed to retain the fan-shaped form more constantly that did smaller ones, there was no special correlation between nuclear number and locomotive form. The floating form of F. calkinsi resembles that of F. citata. (ref. ID; 2298)
  • Cyst: F. calkinsi did not form cysts in culture. (ref. ID; 2298)

    Flabellula citata Schaeffer, 1926 (ref. ID; 2298, 3687, 7710)


    The anterior-posterior dimension of the hyaline zone varied but usually made up approximately 1/4 of the total length. The plasmasol sometimes flowed evenly into the hyaline zone along the entire front but often flowed in more vigorously at one point than others, then spread out, causing temporary slight thickenings in some parts. The anterior margin was often irregular. Part of the hyaline zone was often, cut off by a deep rift as the rest of the zone expanded in another direction, the isolated area often taking the appearance of 1 or 2 clear, conical pseudopods, which passed back along the side. As cytoplasm which had passed back along the sides of the advancing amoeba was gathered into the narrower posterior end, fine uroidal filaments were formed on most amoebae. These filaments, usually about 0.3 um in diameter along most of these length, might be as short as 1/8 the length of the cell or, rarely, as long as the entire main mass. Feeding occurred along the anterior edge, where single bacteria were engulfed in small invaginations, and at the posterior end, where bacteria that had been carried back along the sides were taken in. The cytoplasm behind the hyaline zone contain many small granules, food vacuoles with 1 to several bacteria, and often a few apparently clear vesicles which were not seen to empty. The nucleus, usually in the anterior part of the hyaline region, contained a nucleolus, often irregular in shape, occupying more of the nuclear volume than in most freshwater amoebae. The chromatin layer, usually Feulgen-negative, was apposed to the inner surface of the nuclear membrane. Of 400 amoebae tallied on Kernechtrot preparations from 19-hour-old cultures of strain 90, 386 were uninucleate, 12 binucleate, one trinucleate, and one quadrinucleate. (ref. ID; 2298)
  • Cyst: Cysts were never formed in cultures of these 3 strains, either on agar made with full-strength sea water or on the dilute media. (ref. ID; 2298)