Arcella excavata
Arcella excavata, Ø c. 44 µm – the Netherlands

Arcella excavata  Cunningham, 1919

Diagnosis: Shell colorless or yellowish in young specimens and brown in older cells, oval or circular in apertural view and croissant-like in lateral view; large axis of the shell (length) usually in perpendicular direction to the shell’s protuberances, when the shape of the shell in apertural view is not circular; sometimes the large axis of the shell is parallel to the shell’s protuberances; apertural surface deeply invaginated forming two pronounced protuberances with circular or elliptical aperture at the bottom of invagination; aperture bordered by a small lip; aboral hemispherical region smooth or with regular depressions; shell wall composed of numerous alveoli, made of a proteinaceous material, and arranged in one layer; shell surface smooth or irregular with numerous small pores; usually 3-4 nuclei, sometimes 5-6, with central nucleolus.

Dimensions: Cunningham 55 µm, Stepanek 63-67 µm, Todorov and Golemansky 60-70 µm; my measurements 44 µm (average).

Ecology: Freshwater, on waterplants; also reported from waste water (Todorov, 2003). Rare. I found this species once in considerable numbers in a sample from Crailoo, The Netherlands.

Literature:

Todorov, M. and Golemansky, V.: Morphology, Biometry and Ecology of Arcella excavata Cunningham, 1919 (Rhizopoda: Arcellinida) – Acta Protozool. (2003) 42: 105 – 111.

 

Arcella excavata
Arcella excavata
Arcella excavata
Arcella excavata
Arcella excavata
Arcella excavata
Arcella excavata
Arcella excavata
Recent posts

Raphidocystis glabra

after Zlatogursky et al., 2018 Raphidocystis glabra Dürrschmidt, 1985 Diagnosis: Periplast 40-50 μm in diameter; spine-scales 4.6–15 μm; plate-scales 6-7 × 3-3.5 μm; tiny teeth

Read More »

Raphidocystidae

Raphidocystidae Zlatogursky, 2018 Diagnosis: centrohelids with monolayered plate-scales covering cell surface. Plate-scales with a hollow inflected margin. Sometimes trumpet-shaped or tubular spine-scales present, forming an

Read More »

Planhoogenraadia liboica

P. liboica – from Bonnet, 1979 Planhoogenraadia liboica Bonnet, 1979 Diagnosis: . Test relatively flat, with a dorsal convexity. Shell widest in the center. Aperture deep

Read More »

Deharvengia papuensis

Deharvengia papuensis, after Bonnet, 1979 Deharvengia papuensis  Bonnet, 1979 Diagnosis: Theca large, ovoid, very regular, colorless. Elliptical pseudostome bordered by a thick yellowish lip or

Read More »