Micronereis nanaimoensis sp. n.: with some Notes on its Life-History

Abstract

Micronereis nanaimoensis sp. n. is described from the region of Nanaimo, British Columbia. The definition of Micronereis is slightly emended to include the species. It differs from its only congener, M. variegata Claparède of Europe, in being much larger, in possessing palps, in having more varied setae and different specialized crotchets in the males, and in colour. Swarming, pairing and egg-laying occur from late March to the end of May. The eggs are moulded by the female into masses covered by jelly, which are deposited on leaves of Zostera, Ulva, or other seaweeds, near low-tide mark, and are accompanied by her in the jelly until the larvae become free-swimming. In the laboratory, larvae left the egg-mass after 10–16 days, in cold water. Larval development up to the three-segmented stage is illustrated, and supports the inclusion of Micronereis in Nereidae.