The Development and Setting of a Serpulid Worm, Hydroides norvegica Gunnerus (Polychaeta)

Abstract

Hydroides norvegica larvae were reared to settling in 8-10 days at 20°C. The paired conical processes on the collar setae characteristic of the genera Hydroides and Serpula were developed in the larvae by the sixth day. Settling differed from that recorded for other larvae in that (i) larvae could become attached to surfaces comparatively early in their free-swimming life, (ii) "searching" behaviour followed by settling on a particular locus was not observed, (iii) feeding continued through metamorphosis. The primary operculum of the young worm was formed by modification of the third branchial filament of the left side. Certain identification as H. norvegica could not be made until this had been shed and replaced by a secondary operculum developed from the right side 4-8 weeks after metamorphosis.