Abstract
Ophryotrocha cosmetandra sp.n. is described from shallow-water soft bottoms in Troms and Finnmark, northern Norway. Mature males are morphologically unique in having conspicuous dorsolateral processes on posterior segments and pygidium and a single mid-dorsal funnel-shaped protuberance anterior to pygidium. Other distinguishing characters of the species pertain to jaw morphology, lack of palps and simple parapods without cirri. Only males attain the K-type maxillae.
Courtship and pair formation takes place before egglaying. Fertilized eggs are deposited in a robust tube and brooded by the female. The eggs are very large, being up to 350 µm in length. The larvae develop to the 5-setiger stage in the tube. Early development proceeds slowly taking 30-50 days from spawning to release of larvae.
O. cosmetandra seems to have an arctic-subarctic distribution. The reproductive biology conforms to a common pattern in the genus, while the special traits such as large eggs and slow development fit with well-known adaptations of marine invertebrates in high latitudes.
