Erich ZEECK*, Tilman HARDER, Manfred BECKMANN, Carsten MUELLER
Institute for Chemistry and Biology of the Marine Environment (ICBM), University of
Oldenburg, P.O.Box 2503, D 26111 Oldenburg, Germany
In the marine polychaetes Platynereis dumerilii (Aud. et M.Edw.,1833) and Nereis (Neanthes) succinea (Frey et Leuckart,1847) (Annelida: Polychaeta) sex pheromones are isolated which induce the gamete release in these species.
In both species reproduction strictly depends on an exact spatial and temporal sychronization. High population densities and the synchronization in time are responsible for the formation of swarms near the water surface for reproduction where mate recognition is achieved by chemical signals. After female recognition the male discharges the egg releasing pheromone together with a small sperm cloud. The female is stimulated to swim with high velocity in narrow circles of about 2 cm in diameter, surrounded by males. After an induction period of 10 to 40 seconds the female spawns. The resultant egg cloud contains a sperm release pheromone, and immediate fertilization is achieved by the males circling around the eggs and emitting sperm clouds.
The pheromones were isolated from the coelomic fluid of ripe heteronereids. After ultrafiltration in three steps (10 kD; 1 kD; 0.5 kD) reversed phase HPLC was applied to aqueous samples to isolate the pheromones. Repeated rechromatography of bioactive fractions resulted in single peak fractions. Each step of pheromone isolation was accompanied by tests of the pheromonal activity. Taking into account the possibility of pheromone complexes fractions were tested both single and in combination.
The pheromone causing sperm release for egg fertilization in Platynereis dumerilii was identified by UV-data, analytical microreactions and mass spectrometry to be uric acid. The analytical data and the biological activity of the natural pheromone were exactly reproduced by synthetic uric acid The threshold concentration is 0.6 x10-6 M.
The main compound of the egg releasing pheromone bouquet in Nereis succinea was identified as the ribonucleoside inosine. mainly by 1-H-NMR-spectra. Again the analytical data and biological activity of the natural pheromone were reproduced by synthetic inosine. The bioactivity of inosine is enhanced by two other components of the coelomic fluid of N. succinea males which are emitted together with inosine: glutamine and glutamic acid. Moreover the coelomic fluid contains very small amounts of guanosine which is active, too. The bouquet composition is still under investigation.
Sperm release of Nereis succinea is induced by a tetrapeptide emitted by N. succinea females. According to the 1-H- and 13-C-NMR-spectra (W. Francke, Hamburg) the components are aspartic acid (or asparagine) (2x). glutamic acid (or glutamine) and glycine. Within the reproductiv process the function of the tetrapeptide may be the induction of the first small sperm release of the males after female recognition (see before) (J.D.Hardege, pers. comm.). The details of the structure of the tetrapeptide and its biological function are still under investigation.