4. ANALYSIS OF FACTORS INVOLVED IN SYMBIOSIS
87
activity other than the possibility that the presence of Bucephalus
continuously stimulates their synthesis.
Unlike the situation found in digestive diverticular cells, there is
a significant drop in the amount of total fats stored in the Leydig cells
of parasitized Crassostrea virginica. This reflects decreases of both
neutral fats and fatty acids, thus paralleling the condition noted earlier
in Helisoma trivolvis.
Increases in total lipids in trematode-parasitized mollusca had been
reported earlier by Faust (1917) and Hurst (1927), although von Brand
and Files (1947) found that the fat content in Australorbis glabratus
parasitized by Xchistosoma mansoni larvae remains unchanged. The
increases in total lipids reported by Faust and Hurst could be attributed
to either the initial increase of neutral fats as found in parasitized
Helisoma trivolvis or to the continuous increase as found in the digestive
diverticular cells of Crassostrea virginica. In any event, information is
still too scanty to justify any speculations as to what occurs in molluscs
parasitized by trematodes other than to state that there is definitely a
difference between the changes that occur in parasitized C. virginica
and Helisoma trivolvis as far as the lipids found in the hepatopancreas
are concerned.
There is another aspect of lipid metabolism in intramolluscan
trematode larvae which bears mentioning. Bullock (1948) has reported
that among acanthocephalans fats are synthesized from products of
carbohydrate metabolism by phosphatase activity and that the site of
lipid synthesis is immediately beneath the body surface. In the case of
Glypthelmins pennsylvaniensis, Cheng and Snyder (19624 have found
that fatty acids f i s t appear in developing cercariae at the same site,
thus suggesting a parallel situation, especially since a phosphatase
system is now known to occur in the subcuticular zone of developing
cercariae (Cheng and Snyder, 1962c ; Cheng, 1964a). Indeed Lutta
(1939) has suggested, as I have at the beginning of this section (p. 81),
that there may exist an interdependence between lipid and carbohydrate
metabolism. Lutta’s hypothesis is based on his finding that the greatest
amount of lipids in cercariae are found at sites where the greatest
accumulation of glycogen also occurs.
Little is known about the function of lipids in the intramolluscan
stages of trematodes. Their role in the metabolic production of energy
does not appear to be an important one, since at these essentially
anaerobic microenvironments lipids do not lend themselves to the
internal oxidation-reduction characteristic of anaerobic processes
(Cheng and Snyder, 1962c ; Cheng, 1963d). Evidences contributed by
Ginecinskij (1961) appear to support the hypothesis that lipid meta-
87
activity other than the possibility that the presence of Bucephalus
continuously stimulates their synthesis.
Unlike the situation found in digestive diverticular cells, there is
a significant drop in the amount of total fats stored in the Leydig cells
of parasitized Crassostrea virginica. This reflects decreases of both
neutral fats and fatty acids, thus paralleling the condition noted earlier
in Helisoma trivolvis.
Increases in total lipids in trematode-parasitized mollusca had been
reported earlier by Faust (1917) and Hurst (1927), although von Brand
and Files (1947) found that the fat content in Australorbis glabratus
parasitized by Xchistosoma mansoni larvae remains unchanged. The
increases in total lipids reported by Faust and Hurst could be attributed
to either the initial increase of neutral fats as found in parasitized
Helisoma trivolvis or to the continuous increase as found in the digestive
diverticular cells of Crassostrea virginica. In any event, information is
still too scanty to justify any speculations as to what occurs in molluscs
parasitized by trematodes other than to state that there is definitely a
difference between the changes that occur in parasitized C. virginica
and Helisoma trivolvis as far as the lipids found in the hepatopancreas
are concerned.
There is another aspect of lipid metabolism in intramolluscan
trematode larvae which bears mentioning. Bullock (1948) has reported
that among acanthocephalans fats are synthesized from products of
carbohydrate metabolism by phosphatase activity and that the site of
lipid synthesis is immediately beneath the body surface. In the case of
Glypthelmins pennsylvaniensis, Cheng and Snyder (19624 have found
that fatty acids f i s t appear in developing cercariae at the same site,
thus suggesting a parallel situation, especially since a phosphatase
system is now known to occur in the subcuticular zone of developing
cercariae (Cheng and Snyder, 1962c ; Cheng, 1964a). Indeed Lutta
(1939) has suggested, as I have at the beginning of this section (p. 81),
that there may exist an interdependence between lipid and carbohydrate
metabolism. Lutta’s hypothesis is based on his finding that the greatest
amount of lipids in cercariae are found at sites where the greatest
accumulation of glycogen also occurs.
Little is known about the function of lipids in the intramolluscan
stages of trematodes. Their role in the metabolic production of energy
does not appear to be an important one, since at these essentially
anaerobic microenvironments lipids do not lend themselves to the
internal oxidation-reduction characteristic of anaerobic processes
(Cheng and Snyder, 1962c ; Cheng, 1963d). Evidences contributed by
Ginecinskij (1961) appear to support the hypothesis that lipid meta-