STEROL AND FATTY-ACID COMPOSITION OF NEUTRAL LIPIDS OF PARATENUISENTIS-AMBIGUUS AND ITS HOST EEL

The sterol composition of free sterol and steryl ester fractions of th e 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 glyceroli pids of the parasite, were investigated. The results of these studies were compared with those obtained on the intestinal tract tissue of it s host, the eel (Anguilla anguilla). Cholesterol is the major sterol i n both P. ambiguus and A. anguilla. However, the sterols of P. ambiguu s contain high proportions (>20%) of other sterols, such as campestero l 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. Co nsiderable differences are found in the fatty acid composition of neut ral lipid fractions, as well as the total Lipid extract from the endop arasite as compared to the host tissue. In particular, eicosapentaenoi c 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, The analysis of ether glycerolipids revealed that 1-O-hexadecyl (16:0) and 1-O-hex adecenyl (16:1) moieties were present in similar proportions in the et her lipids of both P. ambiguus and eel intestine, whereas 1-O-octadecy l (18:0) moieties are more prominent in the parasite and 1-O-octadecen yl (18:1) moieties in the eel. The results of these studies show that P. ambguus has specific mechanisms for the regulation of the sterol an d fatty acid composition of neutral lipids.