LIPID DIGESTION IN TURBOT (SCOPHTHALMUS-MAXIMUS) .1. LIPID CLASS AND FATTY-ACID COMPOSITION OF DIGESTA FROM DIFFERENT SEGMENTS OF THE DIGESTIVE-TRACT

The lipid content and lipid composition of digesta from the stomach, f oregut, hindgut and rectum of juvenile turbot fed a commercial diet we re determined in order to examine the process of lipid digestion in th is species. The moisture content of the digesta increased along the di gestive tract from 71.5% in the stomach to 89.6% in the rectum. The li pid content of the digesta increased initially from 15.7% of the dry w eight in the stomach to 36.1% in the foregut but thereafter decreased through 23.2% in the hindgut to 9.1% in the rectum. The proportion of triacylglycerols (TAG) in the total lipid of the digesta decreased fro m 63% in the stomach to 17.4% in the rectum whereas that of free fatty acids (FFA) increased from 10% to 48.9%. The highest proportions of m onoacylglycerols (MAG), diacylglycerols (DAG) and most phospholipids w ere observed in the lipid of the hindgut digesta. In addition, a fall in levels of neutral and phospholipid classes as digesta moved from hi ndgut to rectum signified absorption. Analysis of the fatty acid compo sition of the lipid classes TAG, DAG and MAG suggest a polyunsaturated fatty acid specificity for hydrolysis may exist. Saturated, monounsat urated and polyunsaturated fatty acids (PUFA) accounted for 17.9%, 45. 4% and 37.0%, respectively of the FFA present in the foregut whereas t he corresponding values for the rectum were 32.6%, 51.9% and 16.3%. Ov erall, the results suggest a PUFA specifity for hydrolysis may exist a longside the positional non-specific lipolytic activity associated wit h the hindgut regions of the digestive tract of turbot and that PUFA, released by lipolysis are more effectively absorbed from the digesta t han monounsaturated and saturated fatty acids.