17 November 2008

Rare sand dollars and other surprises

We decided to explore a new shore today and were astounded by the amazing marine life there.Some parts of the silty soft shore were covered thickly in seagrasses; mainly Spoon seagrasses (Halophila ovalis) and Needle seagrasses (Halodule sp.).The seagrasses were teeming with tiny snails, which also dotted the soft silty sand so that it was impossible to walk without stepping on them.A closer look reveals that they are the delightful Dubious nerites (Clithon oualaniensis)! These are among my favourite snails and I so rarely get to see them.Here's a look at the underside (photo on the left) and a tiny bit of the body (photo on the right). The body is striped too, just like the other bigger Nerites (Family Neritidae).I find these snails fascinating because they come in an astonishing variety of patterns.The designs look like they've been patiently drawn with a tiny black marker!Some of the designs are really intricate.And colourful too! The variety seems endless.

The soft shore was also home to lots of moon snails! There were many Tiger moon snails (Natica tigrina) with their spotted shells. Many were in huddles: mating or fighting over food?There was also one Lined moon snail (Natica lineata). I seldom see this moon snail (although we just saw one yesterday at Changi).Indeed, it's been a moon snail fiesta recently and I saw this other moon snail that I've not seen before. It wouldn't come out of its shell so I couldn't see its body. I have no idea what it is!Another mystery snail was this beautiful snail that was ploughing through the soft sand. I saw several of them today! I've seen them in the past at Chek Jawa, but not in recent times. I also have no idea of its identity, but it sure is pretty. Another delightful surprise was this snail. From Tan, K. S. & L. M. Chou, 2000. A Guide to the Common Seashells of Singapore, it's possibly a Bufonaria sp. (Family Bursidae). I've so seldom seen one alive that I've not even done a page for this snail on Wildfacts. From Tan and Chou, "this undetermined species is rare intertidally and usually only seen in dredge samples taken offshore. Very little is known about them." WOW!And among the seagrasses was this Onyx cowrie (Cypraea onyx) which is listed among our threatened animals. Other snails that were abundant on the shores were the Banded creeper snails. There were lots of shells of the Gong gong (Strombus canarium) and of the Black lipped conch (Stombus urceus), inhabited by hermit crabs, but I couldn't find any live ones.

On the soft silty sand was this tiny flatworm.It looks like mobile phlegm. I have no idea what it is. On firmer sand were lots of tubeworms.

The sand was also dotted with little Striped bead anemones (photo on the left). There were several of the large Plain sea anemones (photo on the right). I seldom see more than one of these Plain sea anemones on a trip.There were several Haddon's carpet anemones (Stichodactyla haddoni) and those that were submerged had tiny anemone shrimps living on them. I saw one peacock anemone with its tentacles tucked into its tube, and only one Peachia sea anemone (Peachia sp.).

Soft sand is great for fishes like this flathead (Family Platycephalidae).
There was also one Whiting (Family Sillaginidae), and Andy saw a flatfish. Strangely, I didn't see any little gobies.

The soft sand was dotted with the burrows of snapping shrimps (Family Alpheidae). But I didn't see any other kinds of shrimps. There were a few small swimming crabs, though; and one large Stone crab (Myomenippe hardwicki) in a stone.On the high shore, I chanced upon this gaggle of Land hermit crabs (Coenobita cavipes). They were literally queueing to try out a new empty shell! Well, the queue quickly collapsed into an all out tussle.Here's a closer look at them. There were also lots of Striped hermit crabs (Clibanarius sp.) and lots of tiny little hermit crabs too.

Alas, though I looked, I couldn't find any sea stars. Not even the Sand star or the Common sea star.But there were lots of sea cucumbers. Only one of the Warty sea cucumber (Cercodemas anceps) (photo on the left), but many Thorny sea cucumbers (Colochirus quadrangularis) (photo on the right). I also saw buried Ball sea cucumbers (Phyllophorus sp.) but no Garlic bread sea cucumbers (Holothuria scabra).And I saw this strange sea cucumber. Perhaps it's the Orange sea cucumber? I have no idea.

But the best surprise was to see several Laganum sand dollars (Laganum depressum) of various sizes.Some were a pale pink, and all had a large and prominent petalloid in the centre. This rather pentagonal sand dollar is thick at the edges and at the centre, and thinner elsewhere.In this one, the structures on the undersides were clearer. The spines are longer at the edges.Here's a photo of another of these rarely seen sand dollars. The only time I saw them was on the Sentosa shore that has since been reclaimed for the IR. So it was a real treat to see them today!

Our shores are very much alive! Alas, all too often, raising awareness of our shores often leads to large groups of people going to these special shores. Careless trampling can hurt marine life. Other more destructive behaviour can be even more damaging. So perhaps, for the time being, we should leave this special shore alone.

3 comments:

  1. Thank you for sharing such wonderful photos of these beautiful creatures and f your experiences. I truly enjoyed it and appreciate it very much.
    Michelle

    ReplyDelete
  2. I just found a Laganum sand dollar at Palawan beach, Sentosa yesterday!

    ReplyDelete
  3. Wow, that's nice to hear! Thanks for sharing the find.

    ReplyDelete

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