Saccamoeba stagnicola CCAP 1527/3.
Locomotive forms, cysts.
Olympus BH2, DIC. Scale 20 mkm.
An amoebae strain from Valamo Island
(North-Western Russia) that I beleive to be
Saccamoeba stagnicola. Cyst structure
of this strain (not illustrated) corresponds to that
of S. stagnicola shown above.
MBI 15-2, Phase contrast. Scale 20 mkm.
Basic references for identification:
- Page F.C. (1974) A further study of taxonomic criteria
for Limax amoebae, with description of new species and a
key to genera. Arch.Protistenk. 116:149-184
- Page F.C. (1985) The limax amoebae: comparative fine structure
of the Hartmannelidae (Lobosea) and further comparisons with
the Vahlkampfiidae (Heterolobosea). Protistologica 21:
- Page F.C. 1988. A new key to freshwater and soil
gymnamoebae. FBA, Ambleside. 122p.
- Page F.C. 1991. Nackte Rhizopoda. in: Protozoenfauna,
b.2. Gustav Fisher, Stuttgart. 3-172.
||Saccamoeba stagnicola Page, 1974
(Strain originating from F.C. Page, but not the type strain)
Limax amoeba, subcilindrical in cross-section,
slightly clavate in locomotion.
Frontal hyaline cap is not very obvious, and often is invaded
with the stream of small granules (but not crystals or any other
larger inclusions) from the granuloplasm. Single contractive vacuole
is often located posteriorly or, rare, in the uroid. Typical
villous-bulbous uroid present in most of specimens (uroidal villy
may be not evident under low magnifications, and the uroid may
appear to be morulate or bulbous). Few trailing uroidal filaments
may be seen in amoebae moving in the liqud culture.
Length of the locomotive form 30-75 mkm (average 50 mkm); Length/Breadth ratio about 4.2
Floating form rounded, urregular, with 4-8 short, thick, twisted
Uninucleate, vesicular nucleus 4.5 - 8.5 mkm in diameter
(average 6.5 mkm). Single, central nucleolus often conetins
large lacune and appears to be ring-shape in LM.
Cell contains a number of bypiramidal and plate-shaped crystals
in the cytoplasm.
Cysts rouned, single-walled, 12-19 mkm in diameter (average 15 mkm).
The capacity to form cysts may be lost during the maintenance of
cultures. The strain, illustrated here, formed cysts only in the liquid
culture, but not on the agar.
Cell coat in TEM often appears to be amorphous,
in teh most sucessful preparations it is possible to distinct
very fine cup-like pentagonal structures on the cell surface.
Page (1988; 1991) noted that S.stagnicola often has elongate
mitochondria, in contrast with S. limax.
Despite the seemingly obvious appearnace the identification of
S. stagnicola may be a challenging task. All limax amoebae
are generaly very similar, and it is hard to beleive that their real
diversity is limited with few curently named species. I would offer
to assign an isolate to this species only in case of exceptionally
good fitting of all observed features to the descriptions by
Page (1974; 1988; 1991) and the current description. The
only features that distinct S. stagnicola from S.limax
are the size of the cell (S. limax is generally larger and
more clavate, if to consider Page's strains), the number of crystals
(there is much less of them in S. stagnicola and they are
more fine) and the cyst structure.
TEM is not of much use in species identifiation for hartmannellids,
as the observed details of the ultrastructure of the cell are in great
dependence of the fixation artefacts caused by osmotic shock, differences
in the penetration rate of the fixatives and other reasons. I would offer
even not to rely on the shape of mitochondria, as it is highly variable.
SSU rRNA sequence of both S. stagnicola and
S. limax are available from the
and the comparison of sequences may be very valuable addition for
precise identification of saccamoebians.
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