Lipid, bile acid, water and dry matter content of the intestinal tract of domestic ducks with reference to the habitat of Polymorphus minutus (Acanthocephala).

The data presented in this paper were obtained to define more accurately the environment of Polymorphus minutus, an acanthocephalan parasite of ducks. This parasite inhabits a region of the duck's intestine extending from 60% to 80% of the intestinal length (Crompton & Whitfield, 1968). In the case of Momliformis dubius, an acanthocephalan parasite of rats, Edmonds (1965) found that nutrients are absorbed by the parasite from the host's intestinal lumen rather than the host's intestinal wall with which the parasite makes contact. Thus, nutrients in the rat's intestinal lumen are of prime importance for the growth of M. dubius. This conclusion can probably be applied to P. minutus and other Acanthocephala since the portion of the body wall of these parasites which is exposed to the intestinal lumen is better adapted for nutrient absorption than that embedded in the intestinal wall (Crompton & Lee, 1965). Consequently, analysis of the substances and conditions in the lumen of the region of the intestine inhabited by P. minutus defines the food and other ecological factors in the parasite's environment. In these investigations the total material, lipid and bile acids in five regions of the duck's intestine have been studied. The results enable comparisons to be made between the environment of P. minutus and the other regions of the intestine not favoured by the parasite. Such an approach may provide information about the factors affecting the parasite's selection of its environment. The study of the lipid and bile acid concentrations was also undertaken to obtain evidence about the sites on absorption of the products of lipid digestion, and bile acids. Fats and bile acids are known to be closely associated in the intestine during digestion, but evidence from studies in vitro indicates that fatty acids are absorbed more anteriorly in the intestine than bile acids (Wilson, 1962).