Abstract
Aspects of the biology and data on the frequency of the gall-forming copepod, Antheacheres duebeni M. Sars, are presented, based on regular samples of its host, the sea anemone, Bolocera tuediae (Johnston), in Korsfjorden, western Norway. About half of the Bolocera found were infected by the copepod. Sea anemones of all sizes were parasitized, but big specimens more frequently than small ones. Ovigerous females of Antheacheres have been observed throughout the year, and in hosts of all sizes. Nauplii hatched in the laboratory have lived for about a month, but moulted only once. Up to 300 Antheacheres have been counted in a single Bolocera specimen, but even at this density the parasite does not seem to interfere with the reproduction of its host.