21 September 2008

Crinoids at Hantu

Last night we were on a hunt for feather stars or crinoids! We were fortunate to join Tan Swee Hee and friends from the Raffles Museum of Biodiversity Research who were hosting experts on feather stars Tohru Naruse, Yoshihisa Fujita andMasami Obuchi . We decided to try Pulau Hantu as the best possible spot for finding these animals. And what luck, we found one on the high shore very soon after we arrived.

It was pronounced as rather rare. So it's good that we've been seeing these rather regularly on our Southern shores.Feather stars (Order Crinoidea and thus also called crinoids) are relatives of sea stars and belong to Phylum Echinodermata. They have many feather arms and are a great place for other animals to live on. Such as this tiny red polychaete worm which I really couldn't see in the field (even though it was pointed out to us) and of course, only saw it when I got home to process the photos.

The reef flat was really overgrown with sargassum but we managed to head out to a portion that was relatively clear of the seaweeds.And soon another one was spotted! The water was murky only because so many of us were standing around near it. This feather star is similar to the one we see on our Northern shores as well.And yet another gianormous one was seen soon after. In the great excitement of discovering the animals, I totally forgot to ask what they were. Oops. I was actually very relieved that we managed to see so many crinoids. A total of six. As these are quite rarely seen on the intertidal.

The researchers will also be diving our reefs, where they will have a much easier time at finding them. So we do look forward to learning more about these beautiful animals after their study.

As we had in our team Tan Siong Kiat, one of the authors of the recent paper on new Nerites in Singapore, we badgered him to tell us more about these snails.
And here are three Nerites commonly found on Hantu. These snails are identified by their undersides. The top one is Nerita albicillia, also called the Ox-tongue nerite because of 'pimples' on the broad underside resembles the tongue of a cow. On the left is Nerita chamaeleon and the right is Nerita undata.The special cowrie seen at Sentosa the day before was seen again! And Siong Kiat confirmed that it's Cypraea quadrimaculata! He says they are not really rare but not all that common either. Ah, we must really look at our reefs more carefully.Hantu is a wonderland of hard corals. And we weren't disappointed by the display of healthy and happy corals.There were several large colonies of this very pretty Galaxea sp.Always a delight, the carnation-like Pectinia sp.And a lovely colony of Euphyllia sp. with U-shaped tips to their tentacles.Among the hard corals were strange stuff like this yet-to-be-identified bright green seaweed.Colourful swimming crabs (the ferocious Thalamita spinimana) and large sea anemones. This Giant carpet anemone (Stichodactyla gigantea) had a False clown anemonefish (Amphiprion ocellaris) in it, but it refused to come out for a photo. There were also lots of nudibranchs up and about last night! This one is the commonly encountered Discodoris boholensis.A pretty Gymnodoris sp. Although it looks cartoonish and cute, this animal eats other nudibranchs!And for some reason, very many of these Platydoris sp. nudibranchs.Here's another one of them. The underside is plain white. They are possibly Platydoris scabra.
Also in abundance last night were this black flatworms with an orange and white trim on the edges, possibly Pseudobiceros hancockanus. I saw at least 10 of them! Flatworms can swim for a short distance, as this one demonstrated.There were lots of fishes everywhere, especially the annoying silversides. This half-beak with a shovel-shaped under jaw I've only seen often on Pulau Hantu.

Sijie got a shot of a strange flatworm, and a tiny sea anemone eating a fish.

Throughout the trip, there were many reminders to NOT Step on the Stonefish. And fortunately for us and the fish, we did not step on any. The Hollow-cheeked stonefish (Synanceia horrida) has spines that can penetrate booties and inject a very painful toxin. These fishes are very well camouflaged. Can you see it?Here's a close up of the eye (the tiny dot encircled by filaments) and the huge mouth in a permanent frown. This was a small one, about 10cm long. But these fishes can grow quite large and certainly inspires respect for our reefs.

More about the trip and how to ID crinoids also on the nature scouter blog

More about the crinoid experts on the Raffles Museum News blog

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