Jul 29, 2007

Sea anemones of Sekudu

Another early morning trip with Dr Daphne and the Sea Anemone Team, and wildfilms who abandoned filming for the Anemone Hunt. Again we (vainly) promised NOT to look at Other Lifeforms.

As soon as we landed, we came across these little tentacly creatures.There were lots of them, but Dr Daphne points out that they are NOT sea anemones and are instead Peacock anemones (Order Cerintharia). Cerianthids have an inner ring of shorter tentacles.

There were also some of the usual larger Peacock anemones (photo on the right) where the inner ring of shorter tentacles are more obvious.
We also saw lots of Swimming anemones (Family Boloceroididae) (photo on the left). These anemones are basically a ball of tentacles. You can see the little mouth in the centre of this one.

Dr Daphne told us that these swimming anemones can drop off their tentacles on purpose if they are scared. AND each tentacle can eventually regenerate into a complete new swimming anemone! But NOT ALL sea anemones can do this. In fact, very few can.

We also saw lots of Haddon's carpet anemones (Stichodactyla haddoni).There are identified by their very rounded tentacles that pack together closely on the surface, and by the unique pattern of long-short tentacles at the edge of the oral disk. Tiny transparent shrimp are often found on this sea anemone, often many shrimps on one sea anemone.

But THESE are the sea anemones we came for at Pulau Sekudu.Dr Daphne will take a closer look at them and let us know what they are. I've seen them in large numbers at Sekudu, in smaller numbers on Chek Jawa, and recently on the Sentosa shore that has since been buried under reclamation.

We also looked closely at the large boulders on the island and Dr Daphne found these blobs rather interesting.They were nestled among the mats of tiny clams that form a 'nest' with the byssus threads that they produce. Wow! Let's wait and see what they are.

We tried very hard to find the tiny green sea anemones that Dr Daphne found on seagrasses on Changi. But alas, failed to find any. They are probably really hard to spot.

As we walked, I asked Dr Daphne which came first, the sea anemones or the other tentacly cnidarians like corals? She believes while the first cnidarians were probably something like the modern sea anemone, the sea anemones that we have today are probably more like a solitary hard coral polyp without its skeleton.

In fact, she said, there had been a study where scientists reduced the calcium content of the water in a tank of hard corals. They found that the hard corals stopped producing a skeleton and also stopped their colonial growth and became more solitary. And when they raised the calcium content in the water, the corals reverted to a more colonial growth and resumed producing a skeleton! She also said studies suggest our hard corals today produce 80% less calcium in their skeletons than in the past.

It's just amazing what you can learn just by walking with Dr Daphne. She's such a great teacher.

We wandered off to the rather hard area where we seldom go, as we are usually distracted by the richer seagrass areas.
This area is full of zoanthids or colonial anemones. NOT true sea anemones, these animals can produce toxic substances.

Dr Daphne shared a story of how an aquarium keeper foolishly tried to get rid of zoanthids growing on a rock in his tank. He poured boiling water on the rock and inhaled the resulting steam. He landed up in hospital!! Another good reason NOT to keep a home aquarium?

Although we promised not to look at other animals, we couldn't help but notice the large numbers of white sea urchins among the seaweeds.The sea urchins have a habit of carrying things over themselves, like little shells, bits of dead coral and rubbish. Dr Daphne shared that the bodies of these sea urchin comprise of crystals that some how allow light to penetrate into the body. So they carry things as a kind of umbrella to protect themselves from the sunlight!

I also came across an intact skeleton of a dead heart urchin.
This relative of the sea urchin is an echinoderm, like sea stars. You can see the five part structure of the body in the five-petalled pattern where the tube feet of this animal emerges. The heart urchin is a burrowing animal and is rarely seen above ground. In fact I've only seen the living animal once. When alive, it is covered with spines, like a sea urchin.

Apparently the rest of the wildfilms crew also saw other stuff including their favourite slugs, even though they tried hard to only look for sea anemones. Ron shares more about the trip on his tidechaser blog.

Again, Changi seems much richer in sea anemones that Chek Jawa and Pulau Sekudu. Wow, who would imagine that?! Tomorrow, we'll be checking out Changi and I'm sure we'll see and learn more about the sea anemones there.

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