RESOURCE UTILIZATION BY A SEDENTARY SURFACE DEPOSIT FEEDER, THE ECHIURAN WORM MAXMUELLERIA-LANKESTERI

The feeding behaviour of the shallow-water bonelliid echiuran Maxmuell eria lankesteri is described, based on underwater video recordings mad e in Loch Sween, Argyll, Scotland. We compare the observed utilization of the sediment surface with the systematic grazing pattern inferred for abyssal echiurans from stellate proboscis traces photographed on t he deep-sea floor. M. lankesteri feeds by skimming off the sediment su rface during the linear extension of the proboscis from the burrow ope ning. Successive proboscis extensions did not follow a regular clockwi se or anticlockwise path around the burrow opening. The frequency dist ribution of displacement angles between successive extensions did not differ significantly from random. There was no significant tendency fo r the proboscis to 'follow-up' a successful feed by extending in a sim ilar direction the next time, or for the proboscis to avoid a sector i n which it had previously been disturbed. This unresponsiveness was sh own irrespective of the time elapsed since the preceding extension. Th e orientation of the proboscis also showed no significant relationship to the direction of water flow. There was usually little or no overla p of proboscis feeding strokes on individual nights, but 1 individual which fed on 9 consecutive nights re-used a significantly greater prop ortion of the total area grazed than would be expected if feeding stro kes were made randomly. The feeding behaviour of M. lankesteri differs from the pattern attributed to related deep-sea forms in the lack of a systematic proboscis trajectory and in the willingness to re-use pre viously grazed areas. These differences, if real, may correlate with t he trophic status of the habitat. The ability to concentrate feeding e ffort in specific areas may enable a sedentary deposit-feeder to seque ster ephemeral or patchy food resources by 'caching' material within t he burrow.