The Swimming Performance of the Sea-Anemone Boloceroides

Abstract

1. Boloceroides can swim orally by repeated aboral-oral flexions of its tentacles which make up over 90% of the weight of the anemone. Tentacles at different distances from the mouth beat slightly out of phase, with more marginal tentacles leading more oral ones. Isolated tentacles occasionally give aboral-oral flexions like those of attached tentacles during swimming. 2. Early in a bout of swimming the stroke frequency is about 1·2 strokes/sec. and the swimming velocity about 1·9 cm./sec. The stroke frequency is slightly higher in small animals than in large ones. The swimming velocity achieved is independent of animal size. 3. In tethered swimming the maximum forward force developed during a stroke increases with animal size approximately as the square of the diameter of the tentacle crown. About 8o % of the forward impulse produced during the effective portion of the stroke cycle is negated by rearward impulse during the recovery portion of the cycle. The average forward force for the whole cycle is only about 5% of the maximum force.