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Phylum Cnidaria > Class Anthozoa > Subclass Zoantharia/Hexacorallia > Order Actiniaria
Swimming anemone
Boloceroides mcmurrichi
Family Boloceroididae
updated Oct 2016
if you learn only 3 things about them ...
These animals are everywhere on the shore. Don't step on them!
Don't pick them up. Their sticky tentacles will tear off in your hands.
They CAN swim but usually don't at low tide.

Where seen? Looking like an untidy mop, this anemone is sometimes seen in seagrass areas on many of our

shores. It is possibly seasonal. Sometimes, large numbers are seen (up to 10-20 animals in a trip) and then none at all. Once, we encountered an explosion of countless tiny swimming anemones (less than 1cm across) in the seagrass meadows of Chek Jawa.

Features: Diameter with tentacles extended 5-8cm. The tentacles (3-4cm long) are thick at the base, tapering to slender tips. There are LOTS of tentacles (commonly more than 400). These hide the small oral disk and the mouth, which is on a cone. Some have a white band on the oral disk across the mouth. Sometimes, two of the tentacles near the mouth are prominently lighter. The tentacles are generally shades of brown with bands in darker brown or yellow. Sometimes those with spots, reddish tentacles or white stripes along the tentacle length are see. It has a short semi transparent body column and a small pedal disk which is not very sticky. It's scientific name is pronounced 'boll-loy-sir-roy-dee-des mac-moor-ree-eye'.

Tiny swimming anemones may sometimes be confused with Seagrass anemones which have translucent tentacles with tiny spots.

Does it really swim? Yes it can swim slowly by undulating its many tentacles in a coordinated manner. At low tide, these anemones are often seen loosely attached to seaweeds, or just lying freely on the ground. They are rarely seen swimming about. Possibly they are more active at high tide. Please don't pick up the sea anemone to force it to swim. Its sticky tentacles will come off in your hand and you may hurt the sea anemone.

Losing it: The swimming anemone can purposely drop of its tentacles if it is threatened. The dropped tentacle can wriggle, probably to distract the predator. This dropped tentacle can regenerate into a new swimming anemone after some time. However, almost no other sea anemone does this. So please don't cut an anemone into half hoping to get two anemones. You will instead get no anemone.

What does it eat?
The swimming anemone
harbours symbiotic single-celled algae (called zooxanthellae). The algae undergo photosynthesis to produce food from sunlight. The food produced is shared with the sea anemone, which in return provides the algae with shelter and minerals.


Sometimes with white band next to
the mouth and two paler tentacles.
Pulau Sekudu, Jun 06


Mouth is on a cone in the centre.


Changi, Apr 10

Short body column and small pedal disk.


Explosion of tiny swimming anemones.
Chek Jawa, Oct 10

Many had settled on seagrasses.

Adult (left) compared to tiny one (right).


Reddish with spots.

Cyrene Reef, Aug 11

Reddish with bands.

Cyrene Reef, May 12

Brown with white stripes.

Cyrene Reef, May 12

Swimming sea anemones on Singapore shores

Photos of Swimming anemones for free download from wildsingapore flickr

Distribution in Singapore on this wildsingapore flickr map


Pulau Ubin, Dec 09
Photo shared by James Koh on his blog.

Pulau Sekudu, Oct 11
Photo shared by Loh Kok Sheng on flickr.

Berlayar Creek, Oct 15
Photo shared by Lisa Lim on facebook.


Sentosa, Sep 11
Photo shared by Loh Kok Sheng on his blog.

Terumbu Raya, Jul 07
Photo shared by Marcus Ng on his blog.
 


Pulau Pawai, Dec 09
Shared by James Koh on his flickr.

Sisters Island, Dec 10
Photo shared by Loh Kok Sheng on his blog.

Terumbu Pempang Laut, Apr 11
Photo shared by Loh Kok Sheng on his blog.

Filmed on Sisters Island, Feb 10.

swiming anemone from SgBeachBum on Vimeo.


Filmed on Cyrene Reef, Dec 10.

Swimming anemone @ Cyrene Reef from Loh Kok Sheng on Vimeo.


Links References
  • Daphne Gail Fautin, S. H. Tan and Ria Tan. 30 Dec 2009. Sea anemones (Cnidaria: Actiniaria) of Singapore: abundant and well-known shallow-water species. Raffles Bulletin of Zoology Supplement No. 22: 121-143.
  • Erhardt, Harry and Daniel Knop. 2005. Corals: Indo-Pacific Field Guide IKAN-Unterwasserachiv, Frankfurt. 305 pp.
  • Gosliner, Terrence M., David W. Behrens and Gary C. Williams. 1996. Coral Reef Animals of the Indo-Pacific: Animal life from Africa to Hawaii exclusive of the vertebrates. Sea Challengers. 314pp.
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