Spawning marine Pileworms observed along shoreline.
Observation: Yesterday several people sent photos of a Nikolski, Alaska beach littered with dead marine worms. From the photos I suspect they are Nereis vexillosa Common names: Banner sea-nymph, pile worm, sand worm, mussel worm, clam worm. I won't be sure of the exact species until I receive a sample. You are seeing the masses of dead adult worms on the beaches because both male and females die after spawning. Some people use them as fishing bait. Bruce Wright, Senior Scientist, Aleutian Pribilof Islands Association.
LEO says: As stated in the natural history section of the reference provided by Bruce Wright, "The mating swarms release pheromones into the water which induces mating activity. The male epitokes swarm first and the females will not release their eggs unless in the presence of the males. The eggs are released into the water in the swarms, through ruptures in the body walls. In N. vexillosa the female releases an agglutinating material along with her eggs. Both male and female epitokes (heteronereids) die after spawning. The mass, with eggs inside, sinks to the bottom and grows to about the size of a bluish-green chicken egg. Larvae remain as plankton for hours to months. In the Pacific Northwest the mating swarms usually occur in late winter or spring."
