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N. Sivasothi,
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Raffles Museum of Biodiversity Research, Department of Biological Sciences, National University of Singapore. Since 1998 with origins from OneList.

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Tue 24 Jul 2007

The Swimming Sea Anemone, Boloceroides mcmurrichi

Category : marine

The Raffles Museum of Biodiversity Research is hosting Daphne Fautin, an expert on sea anemones (Phylum Cnidaria: Class Anthozoa: Order Actinaria). She is in town to help identify the Singapore anemones. She has been on several field trips with Singapore's seashore crews and is now immersed in the very tough job of taxonomy which involves dissection and histology.

Last Saturday, she conducted a workshop for some twenty of us and Kok Cheng blogged about it. He mentioned, as I did, the swimming sea anemone; I checked my notes and its Boloceroides mcmurrichi:

Photo by Airani.

Here is Airani's video of B. mcmurrichi swimming. You can hear Daphne Fautin say "This is spectacular behaviour. Because its so coordinated." A rowdy (what else) Ria fills the rest of the audio track, its quite funny.

Excerpts from Josephson & March (1966):

"When the pedal disk is detached the raised tentacles lash downward, driving the animal away from the substrate with the oral end leading. Swimming continues with the tentacles repeatedly and nearly synchronously flexing orally and lashing aborally, each beat moving the animal forward in the oral direction. A full cycle of tentacle movement will be termed a stroke. The stroke frequency during swimming is usually slightly greater than 1 per sec. Swimming bouts are of variable duration, even in a single anemone, and are typically quite short. ...

Boloceroides swims up, down, or horizontally apparently equally well. Often it swims in a nearly straight line, but sometimes the swimming course is rather erratic. The tentacles apparently beat in planes which are slightly inclined to the oral-aboral axis, for the anemone usually rotates about its longitudinal axis as it swims, making a complete revolution every 6-20 strokes. This rotation probably stabilizes swimming to some extent. ...

During swimming the tentacles are functionally organized as a series of concentric rings on the oral disk. During the downstroke portion of the cycle, the most lateral tentacles, the smallest of the crown, are the first to beat. The inner tiers follow in a regular fashion with a brief delay before the onset of lashing in each. The tentacles near the mouth are the last to respond."


  • Photos of the workshop by Airani on Flickr.
  • I. D. Lawn & D. M. Ross, 1982. The Behavioural Physiology of the Swimming Sea Anemone Boloceroides mcmurrichi. Proceedings of the Royal Society of London. Series B, Biological Sciences, 216 (1204): 315-334. [Abstract; JSTOR article on NUS Digital Library (login required)]
  • Josephson, R. K. & S. C. March, 1966. The Swimming Performance of the Sea-Anemone Boloceroides. Journal of Experimental Biology, 44: 493-506. [pdf].

Posted at 12:45PM UTC by N. Sivasothi | permalink | email | Raffles Museum news