Growth and breeding of Spirorbis rupestris (Polychaeta: Serpulidae)

Settlement of young occurred mostly between June and September. Monthly increments in coil diameter of tubes were about 0.5 to 0.7 mm between September and January, but only about 0.2 mm between January and March. Growth seems to continue throughout life, which lasts for about a year. Breeding may begin at a coil diameter of about 2 mm, but is more prolific in larger individuals. Maturation of gametes occurred slowly at 5C, more rapidly at higher temperatures. Spawning occurs between March and October, particularly between April and September. Incubation lasts for much more than a fortnight and there was no trace of the neap tide breeding rhythm seen in closely related species.