Thursday, November 13, 2008

Maxima giant clam at Jong

I finally got to visit Pulau Jong! It is the PAU (bun) island that we always see from the boat whenever it passes by to Semakau.

According to a local legend behind the island's name, a Chinese junk was attacked by Malay pirates one night where the island now is. Just as the pirates were about to board the junk, the captain awoke. When the captain saw the pirates, he uttered such a frightful yell that the sea spirit turned the whole junk into an island.

This small looking island is not just a piece on land with forest, but during low tide you can see its reef extending outwards.

In fact, it is a very charming island in my own opinion with its shape and coastal landforms.

It has natural caves that are carved out when waves hit against the lower resistance portion of the rock formation. You can see the fault lines also very clearly. Like the cliffs at Tanjong Rimau of Sentosa, the formation is pinkish because of iron. It reacts with sea water and result in iron oxide which give it the pinkish reddish glow.

On these magnificient natural cliffs are many types of coastal plants.

And there is one that has purple fruits though I have no idea what is it.

Other coastal plants you can find at Pulau Jong include this seashore pandan.

And also the sea lettuce.

I always cannot resist not taking photographs of the white flowers of the sea lettuce.

On the rocky shores, life is teeming! Each black spot is actually a snail!

Among the many snails and nerites you can find at the high shore, there is this beautiful nerite that is pink with patterns on it.

By looking at the underside, Ria knows the id, which I cannot remember the scientific name already by now.

There are also top shells found at the rocky area.

Instead of the usual egg crabs, the red eyed reef crab is quite common at Jong.

Not forgetting the flora portion, we also saw a couple of seagrass species including this spoon seagrass.

However echinoderms are not too common here, except for the black sea cucumber which are numerous on the Jong-ky shore.

Nevertheless I saw this leafy slug beside two of the black sea cucumbers.

I didn't get to see many nudibranches though except for this polka dot nudi. Later, Chay Hoon shares with us that there are very tiny Gymnodoris slugs on the seaweed which I gave up photographing without trying given my camera's not too excellent macro. Mei Lin got a good shot though, and I hope she can share with us soon.

If you ask us what is most prominent and significant in Pulau Jong, we will reply in unison, "Soft corals!".

Indeed there are MANY large soft corals around the intertidal reef area of Jong. Much more than their hard corals. If you ask why, I personally feel perhaps it's due to the stronger currents??

Just beside another large patch of soft corals, Ria found something special! Can you spot it?

It's an adult giant clam of about 30cm in length! When opened in water, the colourful mantle looks really gorgeous! It's great to have Mei Lin (aka "giant clam girl") to be with us as we get to also somehow see giant clams. Click here to see her pretty face at the Wildshores of Singapore blog.

This girl told us that this is most likely Tridacna maxima which we intertidal people have never seen before (or got it properly identified). The previous sighting was at Raffles Lighthouse during diving in 2003. Now, we are the fortunate few to be able to see it!! Wow!

Next, we had a tough task trying to identify whether it is the elusive T. maxima. Here's the diferent parts that were analyzed to check its identity.

We had to check for its structural makeup and found out that this giant clam has closely stacked and small scutes (fluted projections out from the shell surface) in contrast to the more commonly sighted T. squamosa that we see at Semakau and other southern shores. Also, the surface area of the mantle looks more elongated. This is true because the common name of T. maxima is elongated giant clam.

With the double confirmation by Dr. Peter Todd and Karenne Tun from Marine Biology Lab, NUS, indeed this is the second living elongated giant clam found in our very own local waters (the other at Raffles Lighthouse).

Becauses surveys of our water are not intensive and due to possible misidentification of giant clams, we might have more of this T. maxima which is wonderful!

Below are more photos of this fascinating giant clam.
This is the excurrent siphon which is to clear their excretory products. Mei Lin is studying whether these siphons can probably also aim and squirt water at predators. Indeed, Andy was squirted when he tried to video the clam.

How then can they know that there are predators? This is because they can see! Look closely and you can see the eye spots of the giant clam in this photo (clue: look for the tiny spots at the top).

The giant clams are more colourful than you think. The underside of the mantle can be bright yellow or green, and there's a hint of it from this photo.

I still can't believe that we saw this fascinating giant clam! Yea, finally we can declare that we have seen all the three giant clam species in Singapore intertidally.

And it's so coincidental that when Mei Lin first joined us for southern shore trips, we get to see this rare giant clam that she can helped to find its identification.

1 comment:

Mark Burton said...

I have just seen your blog about "Jong Island" (well thats what we called it). As a young boy My family and another family use to spend every sunday on Jong, that would have been about 1968-1971. Sunbathing, swimming, snorkeling and cooking food on a small fire. I am so suprised at your photographs I have seen. Jong is not how I remembered it. When I was on the island 40 years ago, the water was crystal clear, the reef was untouched, the small beach was covered in "Hermit Crabs" and all you could see.. is sea! no landfill, no oil tankers and no industry plant. I saw my first shark on jong and I was on Jong the first time I saw Concorde fly over. I will look to see if any of my family have any photographs of Jong from 40 years ago just to show how beautiful the island was back in the good old days.

Mark Burton

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