Thanks to Teo Siyang and his team, these curious little purple sea cucumbers that we often see under stones have been identified!
They are Afrocucumis africana!
Considered a widespread and common sea cucumber, it is found in shallow tropical waters from East Africa, India, Southeast Asia, China, Japan and Taiwan to Australia and the Pacific Islands. It is found under loose rocks or coral rubble, clinging on with its tube feet.
The paper shows what its feeding tentacles look like! Something I've never seen as I usually see them out of water at low tide.
As well as the cool teeny tiny ossicles inside the sea cucumber!
Another thing I learnt from the paper is that these sea cucumbers multiply by fission, i.e., by dividing into pieces! Ouch! Here's a photo of another kind of sea cucumber doing this, from an awesome powerpoint by P. Mark O’Loughlin of the Museum Victoria.
Read all about this sea cucumber in the paper: Teo, S., L. C. S. Ng, S. M. Suen, A. F. S. L. Lok & P. X. Ng, 2010. Notes on the sea cucumber, Afrocucumis africana (Semper, 1868) (Holothuroidea: Dendrochirotida: Sclerodactylidae) in Singapore. Nature in Singapore, 3: 65–68. [PDF, 599 KB]
I've also updated the fact sheet on wildsingapore. I thought it's more appropriate to call it the "Little African sea cucumber". What do you think?
Thanks Siyang and team for the ID!