a1 Department of Zoology, Australian National University, Canberra, A.C.T., Australia
The effects of P. burrili adults on the chicken host are outlined. There was no evidence that infections of up to 20 flukes caused marked pathological changes in the nictitating membrane to which flukes attach in an intimate 'placental' manner by the ventral sucker.
The food material of adult flukes is largely lacrimal secretion; it appears that blood can be excluded from the diet since the caecal contents are colourless and haemoglobin was not detected histochemically. Little material was detected in the caeca by the histochemical techniques used. The presence of a mucus coat around flukes was noted and it is suspected that materials of nutritional significance may be conserved in this coat for long periods. Glucose was demonstrated in the parenchyma surrounding the uterus. It is suggested that this might indicate either (a) polysaccharide degradation in this region; (b) polysaccharide synthesis; or (c) a site of accumulation of glucose which enters through the tegument and caeca. The presence of greatest activity in the uterine region may be indicative of nutritional dependence of the developing miracidium on the parent fluke.
The gastrodermis of the caeca is regular, consisting of flattened cells with a very prominent PAS positive, striated border of microvilli. The cytoplasm of the cells contains appreciable amounts of RNA. Protease, acid phosphatase and possibly esterase have been demonstrated in the gastrodermis.
Possible esterase activity occurs in the ventral sucker, alkaline phosphatase is present in the lining of the excretory ducts, and acid phosphatase has also been demonstrated in the pharynx, both suckers, and subcuticular region.
Ferritin was ingested by flukes in vivo and this enabled the digestion cycle to be followed. Flukes ingested little or no ferritin in vitro. Digestion was completed within 13 h and appeared to take place in close association with the striated border rather than in the lumen. The possibilities are that (a) material is digested intracellularly within the microvilli; (b) membrane (contact) digestion takes place; (c) extracellular digestion, in close association with the striated border, takes place. These processes are not necessarily mutually exclusive.
I should like to thank Professor J. D. Smyth for his helpful advice. This study was carried out during the tenure of an Australian National University Research Scholarship.
(Received June 23 1970)