20 April 2010

Sentosa: Staid blobs and galloping star

This morning, we are glad to show Serina of the Tropical Marine Science Institute (TMSI) some of the ascidians on Sentosa. She is preparing for the workshop on ascidians next month.
Here's some of the common ones usually seen on our shores: Little blobs that look like green gum drops, the red striped 'Thumbs up' sea squirt, yellow clustered blobs and some that form layers.

Although Ascidians look like blobs, they are quite complicated creatures. They have organs (like a heart, digestive system) and when they are in their larval stage, they actually have a primitive spinal chord. So they are grouped together with us vertebrates! But they lose this chord as they settle down and become immobile bags that suck in water to filter out edible bits.

Many ascidians are colonial, like the one below. The tiny holes in the slimey layer are the in-current holes of the individual animals, called zooids. Serina shares that the yellowish star shaped things are shared out current holes where stuff is chucked out of the colony.
Some form beige layers (the blobs on the left of the photo) and Serina tells us that these incorporate their feces into the common tissue. Eeks.
Other ascidians are solitary and large. Often looking like sausages, like this orange one.
We spend a bit of time looking under stones where ascidians are often found. So we also encounter other creatures that hide here. Such as this pretty blue-lined flatworm (Pseudoceros sp.).
I also saw several cowries, including this mama Wandering cowrie (Cypraea errones) which was humped over her eggs. See the yellow spots under her large foot? This is why we shouldn't disturb cowries (or other animals) found under stones.
A stone is a great place to attach to, so there are all kinds of animals growing on top of a stone too. Such as these corallimorphs (left photo) and colonies of zoanthids. And this is why we must always put stones the way we found them after gently having a look under them.
Also hiding under stones are bristleworms. While next to stones are pretty fan worms.
There are also all kinds of other animals on this shore. Chay Hoon spotted this small Giant carpet anemone (Stichodactyla gigantea), while there were several large Haddon's carpet anemones (Stichodactyla haddoni) on the sand flats. Tucked in the rubbly areas are nervous Wriggly star anemones and lots of Frilly anemones (Phymanthus sp.).
We also saw fishes! In the pools and water's edge were lots of these little fishies. I don't know what they are. A bunch of them got stranded on the sand, probably by the outgoing tide.
There were also large schools of Crescent perch (Terapon jarbua) swimming in the seagrass meadows.
And once again, we saw an empty egg capsule of either a shark or a ray.
In the water, Chay Hoon spots a rather large Pygmy squid (Idiosepius sp.). It can change colours rapidly!
Sentosa also has echinoderms! There are Common sea stars (Archaster typicus) and Cake sand dollars (Arachnoides placenta) on the sandy stretches. I noticed the sand dollars here leave a yellow stain. I must remember to see if this happens with other sand dollars elsewhere.
But the most special star of the day was found by Chay Hoon! It's the Galloping Sand Star (Stellaster equestris).
It has a very pretty underside and little tube feet with sucker tips.
Read all about this star on Chay Hoon's blog.

I also checked out some of the rare plants seen on this last large natural cliff on Sentosa.

Right opposite this shore, we could see the massive reclamation project at Pasir Panjang to develop a new container terminal there.
Here's a closer look at the huge piles of sand and works going on there.
Other major projects nearby include the construction of a massive boardwalk next to the bridge to Sentosa.

Let's hope these works don't seriously affect these special natural shores on Sentosa.

Other blog posts about this trip
Chay Hoon's colourful clouds

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