Abstract
Although hesionids succeed in the inner Oslofjord, their recruitment variability is not understood because the reproduction biology and the larval development are not known. G. rosea is an important component of the bottom fauna, and the morphology of a complete series of developmental stages from plankton and benthos is illustrated and described, supplemented by larvae reared in the laboratory. The development is planktotrophic. Because of taxonomic problems the adult stage is also briefly illustrated and described to define the diagnostic characteristics of the larvae and juveniles. The metamorphosis and the development of tentacular cirri and parapodia are presented in detail. The larval development of G. rosea is compared with those of other hesionids and pertinent literature is discussed. Finally, the characters that separate G. rosea larvae and juveniles from other corresponding stages of known hesionds, e.g. pigment colour and serrated notosetae, are presented.
