SPAWNING SYNCHRONY IN ARENICOLA-MARINA - EVIDENCE FOR SEX PHEROMONAL CONTROL

Chemical communication systems controlling reproductive behaviour have been shown in a number of marine polychaetes. This study investigated the use of sex pheromones to coordinate spawning behaviour in gravid lugworms (Arenicola marina). Lugworms typically reproduce in the autum n, during low water of spring tides, and often exhibit epidemic spawni ng. Females release gametes within the burrow whereas males deposit sp ermatozoa on to the beach surface. The incoming tide dilutes the sperm atozoa and transports them to the females' burrows. Sperm is diluted r apidly and sperm concentrations fall below the minimum required for fe rtilization within a few minutes. The present investigation establishe s the existence of chemical signals synchronizing spawning for the fir st time in an iteroparous polychaete. The process can be divided into two steps, the induction of gamete release by waterborne chemical cues and burrow irrigation behaviour in females-burrow irrigation represen ting the means by which spermatozoa are carried to the eggs. In both s exes, the release of gametes can be induced by exposure to sea water i nto which other individuals had previously spawned. Males also respond to odour compounds from other males. The overall effect of the chemic al signals results in synchronized, mass spawning of a population.