The Role of Arachidonic Acid and Eicosatrienoic Acids in the Activation of Spermatozoa in Arenicola marina L. (Annelida: Polychaeta)

Partial purification of a sperm maturation factor (SMF) in the intertidal polychaete Arenicofa ma- rina has implicated arachidonic acid, an arachidonic me- tabolite, or a similar substance as the active factor from the prostomium. The effects of a number of 20-carbon fatty acids on inactive spermatozoa are investigated, and this reveals that only arachidonic acid and 8,11,14-eico- satrienoic acid cause sperm activation. The use of argen- tation thin-layer chromatography to separate fatty acids with varying degrees of unsaturation reveals a compo- nent in prostomial lipid extract, which co-migrates with eicosatrienoic acids. Investigations using cyclooxygenase and lipoxygenase result in a loss of sperm-activating properties of both prostomial extract and fatty acids. The use of cyclooxygenase and lipoxygenase inhibitors has no effect. Bovine serum albumin (BSA) reduces the sperm activating properties of both fatty acids and prostomial extract in a dose-dependant way. Additional purification procedures using: (a) organic solvents and aqueous buff- ers and (b) ODS silica cartridges, demonstrate that the active fraction of prostomial extract co-elutes at every step with the 8,11,14-eicosatrienoic acid standard. Gas chromatography of methyl esters of prostomial lipid ex- tract reveals the presence of a peak with an identical re- tention time to the methyl ester of authentic 8,11,14-ei- cosatrienoic acid standard. The results described here provide strong evidence that the active SMF in prosto- mial homogenate is not a fatty acid metabolite but the parent acid 8,11,14-eicosatrienoic acid. These results could only be made unequivocal by full structural analy-