Various isolates. Locomotive forms.
Nikon DiaPhot, Phase contrast.
Vannella simplex CCAP 1589/2. This strain nearly lost its
locomotive capacities due to long culturing, cells are normally
flotate being placed in liquid medium. Few locomotive forms that are
partly abnormal may be found.
Olympus CK2, Phase contrast
Vannella simplex Nivaa isolate (Smirnov et al., 2002).
LM and TEM of cysts.
Photo, TEM: A.Smirnov
Basic references for identification:
- Smirnov AV, Nassonova ES, Holzmann M, Pawlowski J (2002)
Morphological, ecological and molecular studies of Vannella
simplex Wohlfarth-Bottermann 1960 (Lobosea, Gymnamoebia),
with a new diagnosis of this species. Protist 153: 367-377
- Wohlfarth-Botterman K (1960) Protistenstudien. X. Licht- und
electronenmikroskopische Untersuchungen an der amobe
Hyalodiscus simplex n. sp. Protoplasma. 52: 58-107
- Page FC (1976) An Illustrated Key to Freshwater and Soil
Amoebae. Freshwater Biol Assoc, Ambleside
- Page FC (1988) A new key to freshwater and soil gymnamoebae.
Freshwater Biol Assoc, Ambleside, UK
Vannella simplex (Wohlfarth-Bottermann, 1960) Smirnov, Nassonova, Holzmann and Pawlowski, 2002
(type strain - neotype)
The shape of locomotive cells is highly variable. Cells may
be crescent-shaped, with a length/breadth ratio less than 0.5
or fan-shaped, with pronounced "tail" and l/b ratio up to 2.0.
Locomotive form may reach a maximum dimension of 60 mkm; usual
sizes vary from 42 to 50 mkm in length and breadth.
The floating form is of radial type, non - symmetrical,
with one to nine pointed, tapering hyaline pseudopodia without basal
Vesicular nucleus is 6 - 11 mkm in diameter with one central or
slightly eccentric nucleolus. Normally mononucleate, but some strains
tend to have one or two supernumerary nuclei (Page, 1988).
Some cultured strains are always covered with faecal pellets,
whereas others may lose this tendency during cultivation.
Contractile vacuoles always exist in freshwater strains, but
were not found in brackish-water cultures of the V. simplex
Niva isolate (Smirnov et al., 2002).
Simple filaments among the glycostyles of the cell coat may be
absent or indistinguishable in some strains.
Cyst formation was observed in the V. simplex Niva strain
under brackish water conditions, but not in freshwater cultures.
Cysts are rounded, single-walled, with a diameter of 16-26 mkm.
The cell surface inside the cyst is characteristically wrinkled.
The thickness of the cyst wall is 1.1-1.8 mkm.
Habitat: freshwater, brackish-water. Known from numerous locations
in Europe, probably from Asia and North America
Vannella simplex perhaps is among few relatively easily
recognisable amoebae species. However, one should not forget about
the existence of "Vannella cirifera" Frenzel, 1874
(see Page, 1976 for photos of this "species"). Despite the
low-detailed description of this species, it may mean that
there are V. simplex - like species not describet yet.
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