Sabellaria Colonies At Duckpool, North Cornwall, 1961–1970

Abstract

Between May 1961 and November 1970 almost monthly visits were made to Duckpool, an exposed shore on the north coast of Cornwall, where Sabellaria alveolata (L.) is the dominant organism on low-level rocks uncovered only by spring tides. Massive colonies several feet across and up to some 2 ft thick, formed mainly of shell particles cemented together by the worms, as well as many smaller colonies and single tubes, here reach their maximum development in south-west England.Selected sites and colonies were photographed and some measured at frequent intervals over long periods of time. comparative studies of long series of colour transparencies examined closely with a binocular microscope have proved invaluable in elucidating the manner and rate of growth of varied types of colonies, their lengths of life and the manner of their ultimate destruction. Detailed histories of these selected colonies are given in this paper and reveal much that was previously unknown or only guessed.A short spawning period every year in July initiates each new generation. Experimental work, already published, had shown that individuals develop at different rates, the final stage with ability to settle being reached at any time from 6 weeks to 6 or more months, and when reached the ability can be retained for some weeks. This accords with observations on the shore, where settlement takes place in any month between late August and the following early May, or rarely June. The intensity of settlement varies enormously from year to year, there being none in some years, with slight or moderate or heavy settlements in others.