Sunday, November 07, 2010

Huge Chiton at St John's Island

I went to St John's Island with a group of volunteers for an intertidal exploration trip. And finally, I saw an intertidal animal that I had always wanted to see!

Chiton (Acanthopleura gemmata)
This is a Chiton (Acanthopleura gemmata). While this animal may be rather common in some countries, we hardly see them these days in Singapore. This one here was about 8-10cm long. Chitons are molluscs from the Class Polyplacophora, and are characterised by having 8 overlapping plates on their back. Before this, I had only seen the smaller chiton species (less than 3cm long) in Singapore.

Chiton (Acanthopleura gemmata)
The moment I spotted it felt so magically. Just a few seconds before I spotted it, I was just telling another volunteer that I was really hoping to find it one day, though chances were slim. And then, it was there on a huge boulder!

Other molluscan highlights we found include this Galeommatid clam, likely to be a Scintilla philippinensis. In fact, several of these were found under a rock. They are able to move around by pushing using their muscular "foot".

Here's another species of Galeommatid clam. Should also be a Scintilla sp., though it was not as active as the previous one.

Gualtieri's Moon Snail (Natica gualtieriana)
Another nice find would be this Gualtieri's Moon Snail (Natica gualtieriana), which I seldom see on my trips. This fierce snail feeds on other shelled molluscs, such as smaller clams and snails.

Dolphin Snail (Angaria Delphinus)
There was also a Dolphin Snail (Angaria Delphinus) at the rocky shore. It got its name from the shape of its shell, which resembled a dolphin jumping out of water (with a bit of imagination).

Giant Top Shell (Trochus niloticus)
I could usually find Giant Top Shells (Trochus niloticus) here too. These huge shells are over-collected in some places to be made into buttons or for food.

Fan Seaweed Slugs (Costasiella spp.)
On some of the Fan Seaweeds (Avrainvillea sp.), I found a few Fan Seaweed Slugs (Costasiella spp.). Not exactly sure of the IDs of these slugs though. They certainly look somewhat different from the ones I have seen at Semakau. My guess is that the one on top is a Costasiella kuroshimae, while the one below is a Costasiella usagi. And it appeared that some of these slugs might have laid some egg capsules already, looking at the circular egg ribbon nearby!

Sap-sucking Slug (Thuridilla ratna)
There was a tiny Sap-sucking Slug (Thuridilla ratna) which I almost missed due to the currents.

Flatworm (Pseudoceros sp.)
The only flatworm I saw was this one, a Pseudoceros sp. There was just to much sargassum to really properly find things.

Giant Reef Worm (Eunice  aphroditois)
This Giant Reef Worm (Eunice aphroditois) suddenly appeared in front of me, grabbed a mouthful of seaweed, and then quickly retracted back into its burrow.

This animal may look like a worm to some people, but it's actually a fish. This is pipefish, and it's closely related to seahorses. Like the latter, the females deposit the eggs into a pouch on the males' bellies, and hence the males are the ones carrying the eggs until they hatch instead of the females.

Xylocarpus rumphii
I was really glad that I brought the volunteers to see this locally critically endangered plant - Xylocarpus rumphii. There were 3 of them on this part of the shore. It was flowering, but the flowers were way to high up for me to take any decent shots.

And why was I glad that I brought them to see this tree? It was because on the way back from this tree, I had to walk pass a huge boulder which had the chiton on it! That means if I had not brought the volunteers to see this tree, I could have just missed the chiton altogether!

This was certainly my lucky day!

P.S. Pai seh Martina. Did not blog about the Black Sea Cucumber (Holothuria leucospilota) as the only photo I took today was horrible.

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