144
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
Description. Small amoebae, specimens removed from oysters
measure 10-3Op in greatest diameter (average 15p), those grown in
culture may measure 45 p in greatest diameter (average 26.3 p) ;
forward moving surface comprised of large ectoplasmic pseudopodium
which may be multi-branched ; posterior portion of body slightly
elongated, frequently with many small fine ectoplasmic pseudopodia ;
ecto- and endoplasms distinct ; conspicuous refractile granules in
specimens freshly taken from host ; large spherules visible in endoplasm when stained with methylene blue GG or methylene blue R :
normally without contractile vacuoles but vacuoles will appear in
specimens maintained in hypotonic media ; nucleus round or oval, in
endoplasm, with chromatin granules associated with circumkaryosomic zone ; undergo exogenous as well as endogenous budding (Fig. 24).
Cyst opaque, dorsoventrally flattened, round but with irregular edges,
consists of three layers (Fig. 25).
The life cycle of V . calkensi remains incompletely
known although both trophozoites and cysts are known to occur. It is
not known for certain whether oysters become infected through the
ingestion of cysts although this is possible.
Ecology. Nothing is known about the ecology of V . calkensi except
that Hogue (1915)) during culture studies, has noted that it will thrive
not only on isotonic media but also will adapt readily to a hypotonic
one.
Physiology. Hogue (1915), has been successful in culturing V .
calkensi on a semi-solid medium comprised of 1.5% agar prepared with
either sea water or a 0.7% NaCl solution. While on such a medium, the
amoebae thrive on the accompanying bacteria but gradually become
smaller. However, when oyster “ broth ” (body fluids) is added, the
amoebae increase in size. Hogue also has been successful a t culturing
this amoeba on the same agar with 0.4% Witte’s peptone, on agar
containing “ ova mucoid ” and a little egg yolk, and in depression
slides to which sterile oyster “ broth ” is added daily.
Pathology. Apparently V . calkensi does no damage to Crassostrea
virginica. Since it will thrive on bacteria, it is assumed that this amoeba
normally feeds on the intestinal bacterial flora of its host, although it
may be dependent on the host for other requirements. It is not known
whether its relationship with the oyster is obligatory although the
same amoeba has never been found free-living in estuarine waters, but
then the protozoan fauna of oyster beds, as Korringa (1951a) has
pointed out, has not been thoroughly studied.
Life cycle.
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
Description. Small amoebae, specimens removed from oysters
measure 10-3Op in greatest diameter (average 15p), those grown in
culture may measure 45 p in greatest diameter (average 26.3 p) ;
forward moving surface comprised of large ectoplasmic pseudopodium
which may be multi-branched ; posterior portion of body slightly
elongated, frequently with many small fine ectoplasmic pseudopodia ;
ecto- and endoplasms distinct ; conspicuous refractile granules in
specimens freshly taken from host ; large spherules visible in endoplasm when stained with methylene blue GG or methylene blue R :
normally without contractile vacuoles but vacuoles will appear in
specimens maintained in hypotonic media ; nucleus round or oval, in
endoplasm, with chromatin granules associated with circumkaryosomic zone ; undergo exogenous as well as endogenous budding (Fig. 24).
Cyst opaque, dorsoventrally flattened, round but with irregular edges,
consists of three layers (Fig. 25).
The life cycle of V . calkensi remains incompletely
known although both trophozoites and cysts are known to occur. It is
not known for certain whether oysters become infected through the
ingestion of cysts although this is possible.
Ecology. Nothing is known about the ecology of V . calkensi except
that Hogue (1915)) during culture studies, has noted that it will thrive
not only on isotonic media but also will adapt readily to a hypotonic
one.
Physiology. Hogue (1915), has been successful in culturing V .
calkensi on a semi-solid medium comprised of 1.5% agar prepared with
either sea water or a 0.7% NaCl solution. While on such a medium, the
amoebae thrive on the accompanying bacteria but gradually become
smaller. However, when oyster “ broth ” (body fluids) is added, the
amoebae increase in size. Hogue also has been successful a t culturing
this amoeba on the same agar with 0.4% Witte’s peptone, on agar
containing “ ova mucoid ” and a little egg yolk, and in depression
slides to which sterile oyster “ broth ” is added daily.
Pathology. Apparently V . calkensi does no damage to Crassostrea
virginica. Since it will thrive on bacteria, it is assumed that this amoeba
normally feeds on the intestinal bacterial flora of its host, although it
may be dependent on the host for other requirements. It is not known
whether its relationship with the oyster is obligatory although the
same amoeba has never been found free-living in estuarine waters, but
then the protozoan fauna of oyster beds, as Korringa (1951a) has
pointed out, has not been thoroughly studied.
Life cycle.