Mucus-net feeding by the vermetid gastropod Dendropoma maxima in coral reefs

Abstract

Dendropoma maxima (Vermetidae, Mollusca) is the largest member of a conspicuous group of sessile gas- tropods living in shallow tropical and temperate reefs. In the northern tip of the Gulf of Aqaba, Red Sea, individuals of D. maxima live in tubes embedded in the carbonate framework of the reef flat at densities of 11.1 ± 6.3 m -2 . They secrete mucus nets extending ~10 cm around the individuals. The sticky nets billow under the turbulent action of impinging waves and indiscriminately trap suspended particles. The nets are withdrawn at regular intervals and consumed. Net retraction frequency (NRF), as determined by time-lapse video in the laboratory and in the field, appears to be related to particle availability with significant differences between day (1.35 ± 0.16 hauls h -1 ) and night (2.39 ± 0.44 hauls h -1 ), corresponding to differences in the availability of phyto- and zooplankton. With each net load, the snail consumes 10.43 ± 0.99 µg chlorophyll a. Zooplankton accounts for about the same amount of ingested food as phytoplankton, the bulk of which is ingested during the night. Community ingestion amounts to 0.9 ± 0.5 g C m -2 d -1 , showing that mucus-net feeding by D. maxima traps plankton at rates comparable to other sessile suspension feeders in the same coral reefs.