THE ROLE OF A FATTY-ACID HORMONE IN THE REPRODUCTION OF THE POLYCHAETE ARENICOLA-MARINA (L)

Reproduction in the lugworm Arenicola marina is annual and, for most p opulations, occurs in the late autumn or early winter. Oocyte maturati on in females and sperm activation of males and spawning are under hor monal control. In males the polyunsaturated fatty acid, 8,11,14-eicosa trienoic acid, causes both activation of the spermatozoa (Bentley et a l., 1990) and spawning (Pacey and Bentley, 1992). Dissociation of sync itial sperm masses occurs in response to the fatty acid. Active swimmi ng of spermatozoa then follows on dilution in seawater (as a consequen ce of elevation of internal pH, pHi), and fertilization of the eggs ta kes place in the burrow of the female. Sperm activation can also be in duced by arachidonic and 5,8,11-eicosatrienoic acids but not by the 11 ,14,17-isomer. This suggests a possible role for cyclooxygenases or li poxygenases. Sperm activation by the PUFAs is inhibited by nordihydrog uaiaretic acid (50 mu M) and eicosatriynoic acid (13 mu M) suggesting that 12-lipoxygenase acts during activation. Possible involvement of t he fatty acid in co-ordination of reproduction between individuals is also discussed.