world of amoeboid organisms

Arcella megastoma
Large shell, 370 µm in diameter

Arcella megastoma  Penard, 1902

Diagnosis: Shell very flattened with a wide aperture; ratio diameter aperture/shell usually 0.45-0.53; with 2-200 nuclei.

Dimensions: Shell diameter 140-402 µm; apertural diameter 40-216 µm. My measurements: Shell 197-370 µm, apertural diameter 87-190 µm.

Ecology: Freshwater, marshes and ponds, among algae. Common, but never abundant.

Remarks: I have measured the diameter of the aperture and the shell of a number of discoid Arcella specimens from several locations in the Netherlands. The results are plotted in the graph below and show the existence of at least two different groups, probably two species, A. discoides and A. megastoma.

Arcella megastoma
Arcella megastoma
Arcella megastoma, aperture with pores.
Arcella megastoma
Arcella megastoma in lateral view
Recent posts

Pelomyxa video

Pelomyxa palustris Pelomyxa palustris, found below decaying leaves in the hollow of a beech Pelomyxa palustris, found below decaying leaves in the hollow of a

Read More »

Hoogenraadia galeata

H. galeata – from Stepanek, 1963 Hoogenraadia galeata  (Stepanek, 1963) n. comb. Gillardella galeata Stepanek, 1963 Diagnosis: Shell somewhat similar to the shell of Corythion dubium

Read More »

Arcella grospietschi

Arcella grospietschi, after Stepanek, 1963 Arcella grospietschi  Stepanek, 1963 Diagnosis: Shell disc-shaped, yellow-brown, in ventral view with a undulated border, with seven large and seven smaller

Read More »

Arcella oyei

Arcella oyei, after Stepanek, 1963 Arcella oyei  Stepanek, 1963 Diagnosis: In dorsal view, the shell is circular, with 10 apparent broken lobes on the surface. In

Read More »

Centropyxis halophila

C. halophila, after Bonnet, 1959 Centropyxis halophila Bonnet, 1959 Diagnosis: Shell with ovoid sole, extended by a rather strongly covering visor and not clearly separated

Read More »

Euglypha cuspidata

Euglypha cuspidata Euglypha cuspidata  Bonnet, 1959 Diagnosis: Shell small, very transparent, ovoid, in lateral view very elliptical, with sharp edges. Pseudostome small, elliptical, surrounded by a

Read More »