DISTRIBUTION, ECOLOGY AND LIFE-CYCLE OF MAXMUELLERIA-LANKESTERI (ECHIURA, BONELLIIDAE) - A REVIEW WITH NOTES ON FIELD IDENTIFICATION

This paper summarizes the available information on the distribution an d biology of Maxmuelleria lankesteri. This large echiuran was describe d almost a century ago but its local abundance and potential importanc e as a bioturbator were recognized only recently. The species is wides pread around the British and Irish coasts, most commonly in fine muds. A deep-burrowing, nocturnal deposit feeder, M. lankesteri is unlikely to be seen by divers, but its presence can be deduced from the form o f ejecta mounds and proboscis tracks. The worms are very difficult to capture intact. Body size in a sample from Loch Sween, Argyll, was app roximately normally distributed. Very small individuals are rarely fou nd. Developing oocytes were found in the coelom over the spring and su mmer. Mature eggs accumulate in the gonoducts, with maximum loads foun d from October to December, possibly indicating a single annual spawni ng during the winter. Despite intensive examination of a large number of adult females, no dwarf males were found, leaving open the question of their existence. The large, yolky eggs indicate lecithotrophy or d irect development. Larval stages have not been recognized. The apparen t scarcity of developmental stages and of very small adults suggests t hat recruitment may be sparse and infrequent.