Feeding mechanism of the polychaete Sabellaria alveolata revisited: Comment on Dubois et al. (2005)

Abstract

Recently, Dubois et al. (2005; Mar Ecol Prog Ser 301:159-171) described the feeding mechanisms of the sabellariid polychaete Sabellaria alveolata and concluded that it is a ciliary suspension feeder that uses alternately a downstream- and an upstream-collecting system. We reinvestigated both the ciliated epithelia (scanning electron microscopy and transmission electron microscopy) and the function (video microscopy) of the tentacle crown of S. alveolata. We found that the tentacles of intact and undisturbed S. alveolata have a large number of stiff ciliary spikes, each flanked by an actively beating cirrus, but no structured flow of water is created and only minor local currents can be seen. Clearly, S. alveolata has neither a ciliary downstream-collecting system nor a proper ciliary pump as found in upstream-collecting bryozoans, phoronids and brachiopods. Our findings indicate that S. alveolata's tentacle crown is designed for passive suspension feeding and thus dependent on ambient currents to bring suspended food particles into contact with the tentacles. The significance of the conspicuous ciliary spikes remains unknown, but our observations suggest that mucus is involved in both capture and transport of food particles. © Inter-Research 2006.