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 and biology of Maxmuelleria lankesteri. This large echiuran was described almost a century ago but its local abundance and potential importance as a bioturbator were recognized only recently. The species is widespread 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 of ejecta mounds and proboscis tracks. The worms are very difficult to capture intact. Body size in a sample from Loch Sween, Argyll, was approximately normally distributed. Very small individuals are rarely found. Developing oocytes were found in the coelom over the spring and summer. Mature eggs accumulate in the gonoducts, with maximum loads found from October to December, possibly indicating a single annual spawning 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 direct development. Larval stages have not been recognized. The apparent scarcity of developmental stages and of very small adults suggests that recruitment may be sparse and infrequent.