Platynereis lives in tubes which it has spun itself and which are attached to the bottom. Sexually mature animals (Heteronereis) leave their dwelling tubes in co-ordination with the time of day and the phases of the moon. In their mating dance the females swim in tight circles; the males, in wider ones around them; and both release their sexual products into the ambient water. Subsequently, the empty husks die. The trochophore larvae develop into the juvenile worm without feeding. While new body segments develop at the posterior end, the anterior parapodial pair is transformed from a locomotory to a sensory appendage.