The sterol composition of free sterol and steryl ester fractions of the fish parasite Paratenuisentis ambiguus was determined. In addition, the fatty acid composition of various neutral lipid classes, i.e., wax esters, steryl esters, triacylglycerols and free fatty acids, as well as the composition of the 1-O-alkyl moieties of total ether glycerolipids of the parasite, were investigated. The results of these studies were compared with those obtained on the intestinal tract tissue of its host, the eel (Anguilla anguilla). Cholesterol is the major sterol in both P. ambiguus and A. anguilla. However, the sterols of P. ambiguus contain high proportions (> 20%) of other sterols, such as campesterol and various dehydrosterols. [e.g., 7-dehydrocholesterol and cholesta-5,22(E)-dienol]. The presence of these minor sterols agrees with the known biotransformations of exogenous sterols in various helminths. Considerable differences are found in the fatty acid composition of neutral lipid fractions, as well as the total lipid extract from the endoparasite as compared to the host tissue. In particular, eicosapentaenoic acid (20:5n-3), other polyunsaturated fatty acids, such as 20:4n-6, 22:5n-3 and 22:6n-3, as well as long-chain saturated fatty acids, such as 20:0, are generally enriched in the neutral lipid fractions of the parasite as compared to those of infected eel intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

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Specific differences between the acyl composition of lipids of the helminth Paratenuisentis ambiguus and its host eel, as shown previously, prompted us to study the lipid metabolism in this intestinal fish parasite. Adults and larvae of P. ambiguus were fed various lipid precursors, e.g., fatty acids, long-chain alcohols and 1-O-alkylglycerols, which may occur as common nutrients of intestinal parasites. Incorporation of [1-14C]palmitic acid into neutral and polar lipids was found to be similar under aerobic and near-anaerobic conditions. In adult parasites maintained in culture medium supplemented with glucose, [1-14C]palmitic acid was incorporated mainly into triacylglycerols and phosphatidylcholines, whereas [1-14C]oleic acid was incorporated preferentially into triacylglycerols. In fasted adults, as well as in larvae, [1-14C]oleic acid was mainly transferred to phosphatidylcholines. Lipolytic activity was detected in adult parasites that had been incubated with radioactive trioleoylglycerol. [1-14C]Hexadecan-1-ol was oxidized in P. ambiguus at a high rate to labeled palmitic acid, which was incorporated into various lipid classes of P. ambiguus. Small but significant proportions of radioactivity from hexadecan-1-ol were incorporated into ether glycerolipids of the parasite. A more direct precursor in ether glycerolipid metabolism, i.e., rac-1-O-[1'-14C]hexadecylglycerol, was incorporated into alkyl and 1'-alkenyl moieties of choline and etha-nolamine ether-glycerophospholipids of P. ambiguus in high yield. High proportions of labeled diacylglycerols, triacylglycerols and steryl esters were detected in surface lipids as well as lipid extracts of the culture media after incubation of P. ambiguus with [1-14C]palmitic or [1-14C]oleic acids.(ABSTRACT TRUNCATED AT 250 WORDS)