4. ANALYSIS O F FACTORS INVOLVED I N SYMBIOSIS
71
example, Chernin (1962) has found that the eggs of the nematode
Daubaylia potomaca do become encapsulated in the snail Helisoma
caribaeum.
c. Leucocytosis
Very little is known about the cause and function of this type o
internal defense mechanism. I n fact, it remains to be clarified as to
whether this should be considered a distinct type of defense mechanism
or should be considered as a manifestation of early stages of phagocytosis, encapsulation, or both. Leucocytosis is manifested as an
increase in the number of amoebocytes. Although this phenomenon is
well known among vertebrates and certain invertebrates, it has not
been studied to any extent among molluscs. Stauber (1961) reported
that Feng and Canzonier (unpublished data) have found that the
number of leucocytes in C. virginica is increased within 24 h after
intracardial injection of even sterile sea water. He stated that “ the
proportions of the various types of blood cells may also change after
the injection for foreign materials (ink, bacteria) or even after
hemorrhage.” Cameron (1 934) has described a similar phenomenon in
the larvae of the wax moth caterpillar.
The difficulty in evaluating and explaining leucocytosis in oysters,
or in any mollusc for that matter, rests with the fact that the normal
leucocyte count of molluscs is difficult t o ascertain due to difficulties
in sampling and normal fluctuations. Furthermore, except for the report
by George and Ferguson (1950) on Busycon carica, B. canaliculatum
and Fasciolaria tulipa, and a few earlier workers (cited by George and
Ferguson), the types of leucocytes present and their normal ratios have
not been studied.
Recently, Feng (1965b) has published his data. He has found that
the number of circulating leucocytes from heart blood samples increases
linearly with rising ambient temperatures a t which the oysters are held.
Concurrent with the rise in leucocyte count, the corresponding heart
rates increase (Fig. 14). He concluded that the fluctuation of leucocyte
counts in oyster blood is probably associated with the intensity of
agitation exerted by the heart beat, which in turn is influenced by the
ambient temperature. Feng has also demonstrated that repeated
bleedings do not effect the heart rate nor the number of leucocytes,
while injections of sea water and spinach chloroplasts reduce, rather
than elevate, the heart rate and leucocyte count significantly for a
period of 2 to a t least 4 h. His findings need not contradict Stauber’s
original reference to this work, although it may. Actually, Feng
counted free circulating blood cells which by no means represent all
71
example, Chernin (1962) has found that the eggs of the nematode
Daubaylia potomaca do become encapsulated in the snail Helisoma
caribaeum.
c. Leucocytosis
Very little is known about the cause and function of this type o
internal defense mechanism. I n fact, it remains to be clarified as to
whether this should be considered a distinct type of defense mechanism
or should be considered as a manifestation of early stages of phagocytosis, encapsulation, or both. Leucocytosis is manifested as an
increase in the number of amoebocytes. Although this phenomenon is
well known among vertebrates and certain invertebrates, it has not
been studied to any extent among molluscs. Stauber (1961) reported
that Feng and Canzonier (unpublished data) have found that the
number of leucocytes in C. virginica is increased within 24 h after
intracardial injection of even sterile sea water. He stated that “ the
proportions of the various types of blood cells may also change after
the injection for foreign materials (ink, bacteria) or even after
hemorrhage.” Cameron (1 934) has described a similar phenomenon in
the larvae of the wax moth caterpillar.
The difficulty in evaluating and explaining leucocytosis in oysters,
or in any mollusc for that matter, rests with the fact that the normal
leucocyte count of molluscs is difficult t o ascertain due to difficulties
in sampling and normal fluctuations. Furthermore, except for the report
by George and Ferguson (1950) on Busycon carica, B. canaliculatum
and Fasciolaria tulipa, and a few earlier workers (cited by George and
Ferguson), the types of leucocytes present and their normal ratios have
not been studied.
Recently, Feng (1965b) has published his data. He has found that
the number of circulating leucocytes from heart blood samples increases
linearly with rising ambient temperatures a t which the oysters are held.
Concurrent with the rise in leucocyte count, the corresponding heart
rates increase (Fig. 14). He concluded that the fluctuation of leucocyte
counts in oyster blood is probably associated with the intensity of
agitation exerted by the heart beat, which in turn is influenced by the
ambient temperature. Feng has also demonstrated that repeated
bleedings do not effect the heart rate nor the number of leucocytes,
while injections of sea water and spinach chloroplasts reduce, rather
than elevate, the heart rate and leucocyte count significantly for a
period of 2 to a t least 4 h. His findings need not contradict Stauber’s
original reference to this work, although it may. Actually, Feng
counted free circulating blood cells which by no means represent all