72
MARINE MOLLUSCS AS H O S T S FOR SYMBIOSES
the Ieucocytes present in the heart since it is known that there is some
sludging of leucocytes induced by temporary heart failure. Similar
cell clots have been reported by Bang (1961).
Since leucocytosis obviously suggests the rapid formation of leucocytes within the mollusc’s body, the question arises as to where the
hemopoetic sites are within a mollusc? Surprisingly, such sites have yet
to be convincingly demonstrated, especially in pelecypods. It is noted,
however, that Haughton (1934) and Wagge (1951, 1955) have expressed
. . . . . . . . . . .
35
30
25
20 ;
c L
0
15 f
0
i
10
- 5
- 0
0 2 4 6 8 10
140
18
24
Temperature c
FIG. 14. Tho effect of temperature on leucocyte number and heart rittr of oysters,
Crnssostrea virginiccc. Each point rcprosents the average hoart rate of three determinations on ten oysters. The vertical lines are ranges of the means. (After Fang,
1965b.)
the opinion that molluscan leucocytes arise via the differentiation of
fibroblasts and epithelial cells, a concept which cannot be accepted
without critical testing. Pan (1958) has reported that in Australorbis
glabratus the hemopoetic sites are the walls of the saccular portion of
the kidney and the blood sinuses. Certainly further studies on both the
types of blood cells and hemopoetic sites in molluscs should be encouraged. It is evident that eventual better understanding of all types
of cellular reactions in molluscs, including leucocytosis, phagocytosis