Abstract
Nereimyra punctata, which occurs in two colour varieties in the polluted Oslofjord, is an important component of the fauna, but its life history has been incompletely known. The adult stage is briefly illustrated and described to define the diagnostic characters of larvae and juveniles. A series of developmental stages is figured and described based on wild-caught planktonic and benthic larvae. N. punctata spawns in spring, and the pelagic larvae develop transitory setae on the second and third segments (tentacular segments in adults) before they settle on the bottom between April and August. A median prostomial antenna develops early in the bottom stage but is lost in adults. The benthic larvae grow fast and increase from c. 0.5 mm to 2–3 mm (juveniles) in 4–6 months. A further 11/2 years of growth elapse before spawning takes place. The pelagic larvae can be distinguished from other hesionids by their poorly developed head appendages, red eyes, long dorsal cirri on segment 2, lack of ventral cirri on segment 3 only, and the presence of a projection between the anal cirri. The larval stages of Ophiodromus flexuosus, Gyptis rosea, and Nereimyra punctata are compared.
