28 December 2011

Mission anemone at Pasir Ris

I'm on a mission at Pasir Ris to take a closer look at some curious anemones, but also had a chance to have a quick look at the shore here.
There's a bloom of Sea lettuce seaweed (Ulva sp.), normal for this time of the year. Large areas are covered in mats of Nest mussels (Musculista senhousia).

Here a closer look at the tiny mussels. These tiny mussels build communal 'nests' with their byssus threads incorporating sediments, bits of broken shells and other debris. Large areas can be covered in such 'nests', pockmarked with little slits, each housing one mussel. After the massive flooding at Chek Jawa in 2007 that led to mass deaths there, mats of these mussels were also seen at Chek Jawa. Fortunately, yesterday I didn't see signs of mass deaths at Pasir Ris, although it has been a very wet monsoon season.
When the sun set, the stars came out. Sand stars (Astropecten sp.)! There were lots of them.
There were lots of pink Ribbon worms (Phylum Nemertea) on the sand. Some were very long, but others like this one with a black head were shorter. It took me a while before I realised I was shooting its butt instead of its head!
Here's a closer look at the head of the worm.
I came across a lively Razor clam (Family Solenidae) that was moving about on the surface with its large muscular foot. Wow, see how the base of the foot forms a kind of triangular wedge. This is probably how the clam manages to dig rapidly into the sand. Using the wedge to get a grip, then contracting to pull the smooth shell into the sand. The tube at the other end of the shell is its siphon.
Abundant on the shore were Tiger moon snails (Natica tigrina). I saw about twenty of them! I've never seen so many before on one trip.
My main mission was to take a closer look at these commonly seen burrowing anemones. Often seen in silty sandy areas, I've grouped all similar anemone here. But are they all the same? Dr Daphne Fautin, world authority in sea anemones, is kindly looking into these beasts and would like to know what they look like when alive. In particular their oral disk and body column.
Here's one that has pink tentacles. But structurally, it looks similar to the rest.
Another one that looks similar.
This one was tiny and stuck to plastic litter. I forgot to take a photo of its body column when I was in the field.
This one looks slightly different, but not much more.
When I took a closer look at it, there was a miniature sea anemone with it! Is the anemone a brooder and did it just spit out a 'baby'? I have no idea.
This one had black tentacles. But otherwise looks very similar.
There were other anemones on the shore too. Tiny anemones had settled on little snails. Here's one whelk (Family Nassaridae) with at least seven little anemones on its shell! Despite its burden, the snail was moving rapidly!
Here's another buried whelk with only its long worm-like siphon sticking out of the sediment, with at least one anemone stuck on its shell.
I also saw one very small Mangrove anemone with petals around its mouth.
There's so much more to learn about our shores!

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