Riisgård HU, Nielsen C

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

MEPS 328:295-305 | Full text in pdf format

 

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• Video clip #1 shows a laterofrontal view of a tentacle of an intact Sabellaria alveolata, with the tentacle tip to the upper left. The tentacle has a large number of stiff ciliary spikes, each flanked by an actively beating bundle of compound cilia (cirri). No structured flow of water is created by the rather non-periodically beating cilia and only minor local currents are seen. Clearly, S. alveolata do not possess a proper ciliary pump as typically found in true ciliary suspension feeders. This indicates that S. alveolata's tentacle crown is designed for passive suspension feeding and thus completely dependent on ambient currents that bring suspended food particle into contact with the tentacles. The flow-technical significance of the ciliary spikes remains unknown.
• Video clip #2 shows the expanded tentacle crown of an intact Sabellaria alveolata in its natural tube in a colony. Seston particles added to the observation aquarium are seen frequently to encounter the tentacles to be retained, possibly by mucus adhesion. The captured particles are subsequently transported towards the base of the tentacle. Capture of a particle is, often after a time lack of 0.5 to 2.5 s, succeed by a rapid bending of the tentacle tip. Frequently, this bending continues into a spiral like contraction of the whole tentacle whereby particles stuck in mucus on the frontal side are rounded up in larger lumps to be transported further downwards on the frontal side towards the base of the tentacle. During the rapid tentacle bending/spiralling captured particles do usually not lose contact to the surface of the tentacle. The tentacle crown of a small rival, the actively filter-feeding polychaete Fabricia sabella, is seen to the right in the picture.
• Video clip #3 shows particle catch-up in Fabricia sabella