01 August 2012

Colourful Changi with Motherload of Seagrass anemones

Changi is an easy place to explore on the mainland, with lots of colourful marine life. The only catch is we need to go out at super low tide, which happened at 3.30am this morning!
A great encounter: the Pink warty sea cucumber (Cercodemas anceps) and the Thorny sea cucumber (Colochirus quadrangularis), BOTH with their feeding tentacles extended. A nice photo to show the differences between these similar looking creatures. Today we also came across lots of Seagrass anemones and some strange snails we've never seen before.

Another colourful creature that recently became common on Changi is the painfully pink  Pink sand dollar (Peronella lesueuri). Often buried just beneath the sand, I saw more of these today than the usually more abundant purply Cake sand dollars (Arachnoides placenta).
I saw two lovely Noble volute (Cymbiola nobilis), hunting for buried prey with their swiveling siphon. These beautiful animals look so handsome alive and I'm glad they were not taken away by the small group of other people who were also on the shore. On my last trip here in May, I saw a clam make an amazing escape from a hunting Noble volute.
I didn't see many sea stars today, just a few Painted sand stars (Astropecten sp.) and one small Biscuit sea star (Goniodiscaster scaber). But Marcus saw a Common sea star (Archaster typicus).
Other colourful creatures include sea cucumbers. I saw two Remarkable sea cucumbers (Holothuria notabilis) and several orange sea cucumbers. There were lots and lots of buried Ball sea cucumbers (Phyllophorus sp.) and Smooth sea cucumbers.
I was a little confused by this tangle of weird bumps until I realised I was looking at a half-buried Beige sea cucumber with its feeding tentacles extended. The other lump is an encrusted shell occupied by a hermit crab.
As usual, I tried out the new intertidal survey method on this shore. It really does force me to observe the shore more closely. During the survey I saw lots of large Window pane clams (Placuna sp.) many of them very large, and Fan clams (Family Pinnidae), several Hammer oysters (Malleus sp.), many Ball moon snails. There were also lots of White sea urchins (Salmacis sp.), with much fewer Black sea urchins (Temnopleurus sp.). Also patches with many sea pencils, while Ball sea cucumbers (Phyllophorus sp.) seemed everywhere. I only saw a few flowery sea pens (Family Veretillidae) and some cerianthids (Order Ceriantharia). Here's a slideshow of the transects for today's survey.
Compared to my last trip here in May, I noticed there is a lot less seagrass today and the shore seems a lot sandier. Although all the seagrass species were still there: Needle seagrass (Halodule sp.), Spoon seagrasses (Halophila ovalis) and Fern seagrasses (Halophila spinulosa). It was dark during our trip, so I'm not sure if this is because the sand bar had shifted, thus the lagoons with seagrasses are no longer created on the shore? I'll  be back here on Friday and have a look at the situation in daylight.

The special finds today include the Motherlode of Seagrass anemones! I've been finding these tiny anemones in ones or twos on various shores by painfully looking at seagrasses closely. But this morning, Marcus found a small patch teeming with them!
Although at first glance they do resemble tiny Swimming anemones (Boloceroides mcmurrichi), the Seagrass anemone has a rather longer body column with lots of bumps. Its tentacles are also more spotted while the Swimming anemones tend to have more banded tentacles. To add to the confusion, the Seagrass anemone also 'swims' by undulating its tentacles, but not as vigorously and only for a very short while. I observed one Seagrass anemone moving to a new position by reaching out with its tentacles, then unclamping its foot and pulling itself to its new spot with its tentacles to re-attach its foot to its new location.
When alarmed, the sea anemone may to contract its body column and flatten out against the seagrass blade.
I took a much closer look at these fascinating creatures. The body column can extend quite a bit, the bottom is usually opaque with bumps while the animal is transparent near the top. The tentacles have fine dark rings where they attach to the oral disk. And it seems to have a narrow thing in the middle of its mouth that it can extend out of the mouth. This thing has 'fingers' on the ends, which reminds me of the fingers in the middle of the mouth of a  Peachia anemone (Peachia sp.). The anemone produces quite a lot of slime when it's disturbed.
There were also other tiny sea anemones stuck to seagrass blades on the shore today. But these are probably baby Carpet anemones (Stichodactyla haddoni) as they have short stumpy tentacles on a broad oral disk and very short body column.
These tiny anemones were stuck to the shell of a hermit crab! They look like a small version of the huge sea anemones found on hermit crabs.
Amid the excitement of looking at anemones on seagrasses, I almost dismissed this odd looking thing next to the sea anemones that looks like a rather coarse and lumpy sea anemone. It turned out to be some kind of slug! Chay Hoon will be sorting out its identity soon.
Another exciting find was this strange snail that none of us have seen before. There were two small ones chasing a larger one. Mating time?
Mei Lin found one with a nicer shell. In the others, the darker colouration had peeled off leaving behind a white shell. We have no idea what these are.
Mei Lin also found this clam which I've never seen alive before. Since we've just attended Dr Tan's awesome Bivalve Workshop, must make an effort to find out what it is. Of course, it's still alive so we can't mess around with its insides, but from the beautifully sculpted shell, it seems be Placamen calophylla a kind of Venus clam (Family Veneridae).
It's amazing what we can discover and learn even though we visit our shores so often. The tide turned well before dawn and everyone went back to work at sunrise. MORE predawn trips over the next two days. It's tough, but we love the morning trips and will miss them when they end in September.

The rest of the team also had marvellous sightings which I'm sure they will share soon.

Today, the Malaysian press reported that the car ferry system that leaves from the nearby Changi Ferry Terminal will resume by the end of next year. Let's hope the increased traffic doesn't affect this lovely shore.

Posts by others on this trip
  • Mei Lin shares about her two trips here as well as her busy week at a conference of taxonomists


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