METABOLISM OF LONG-CHAIN FATTY-ACIDS, ALCOHOLS AND ALKYLGLYCEROLS IN THE FISH PARASITE PARATENUISENTIS-AMBIGUUS (ACANTHOCEPHALA)

Specific differences between the acyl composition of lipids of the hel minth Paratenuisentis ambiguus and its host eel, as shown previously, prompted us to study the lipid metabolism in this intestinal fish para site. Adults and larvae of P. ambiguus were fed various lipid precurso rs, e.g., fatty acids, long-chain alcohols and 1-O-alkylglycerols, whi ch may occur as common nutrients of intestinal parasites. Incorporatio n of [1-C-14]palmitic acid into neutral and polar lipids was found to be similar under aerobic and near-anaerobic conditions. In adult paras ites maintained in culture medium supplemented with glucose, [1-C-14]p almitic acid was incorporated mainly into triacylglycerols and phospha tidylcholines, whereas [1-C-14]oleic acid was incorporated preferentia lly into triacylglycerols. In fasted adults, as well as in larvae, [1- C-14]oleic acid was mainly transferred to phosphatidylcholines. Lipoly tic activity was detected in adult parasites that had been incubated w ith radioactive trioleoylglycerol. [1-C-14]Hexadecan-1-ol was oxidized in P. ambiguus at a high rate to labeled palmitic acid, which was inc orporated into various lipid classes of P. ambiguus. Small but signifi cant proportions of radioactivity from hexadecan-1 ol were incorporate d into ether glycerolipids of the parasite. A more direct precursor in ether glycerolipid metabolism, i.e., rac-1-O-[1-C-14]hexadecylglycero l, was incorporated into alkyl and 1'-alkenyl moieties of choline and etha-nolamine etherglycerophospholipids of P. ambiguus in high yield. High proportions of labeled diacylglycerols, triacylglycerols and ster yl esters were detected in surface lipids as well as lipid extracts of the culture media after incubation of P. ambiguus with [1-C-14]palmit ic or [1-C-14]oleic acids. The results suggest that palmitic acid and oleic acid are incorporated into neutral and polar lipids of P. ambigu us maintained in glucose medium quite differently with oleic acid show ing a strong preference for triacylglycerols. However, the incorporati on of palmitic acid in glucose-fed parasites was similar to that of ol eic acid in fasted parasites, as well as in larvae. This may be explai ned by partial fatty acid depletion in fasted worms and rapid cell div ision in larvae, respectively.