Monday, July 16, 2007

Semakau Inter-Tidal Walk on 15 July 2007

Seventeenth Discovery Posting:

(Entry @ 28 Dec 2007: Sixth 'discovery''s ID may be wrong, it might be a a colony of Euphyllia corals and not Heliofungia (mushroom coral), thanks to Ria for pointing this out)

After last month's very wet visits to Semakau, all of us were hoping for a clear morning for the walk. And the clear night sky (around 5am, the time we were meeting) was a first indication that we were going to have great weather. Now we just need the luck to 'discover' many things.

The group i was leading was 'clown fishes' and it was a small group, they were a family and this was the second time that they were going to Semakau (for the family's Dad, it was his first time)

Anyway, let's talk about the first 'discovery' of the morning after we 'hit' the inter-tidal zone after 'bashing' through the forest trail in the dark. Lots of common Sea Stars (picture below).
Discovery Note:
1. Although people commonly call them star fish, we prefer to call them sea stars. As they are not fishes.
2. If you look on the underside of the sea star, you will find the tube feet of the sea star.
3. These tube feet are used for walking, handle food as well as breathing, talk about multi purpose!
4. Sea stars get stressed when out of water, so please don’t take them out of the water for too long.

5. Some sea stars possess more than 5 'limbs', as you can see from the picture above.

After we crossed the sea grass lagoon, we saw the second 'discovery' which was a sandfish sea cucumber (picture below).
Discovery Note:
1. Being related to the sea stars, sea cucumbers have a soft, wormlike body and range from a few centimeters to 90 centimeters in length.
2. Unlike the sea star, however, they have no arms but use a cluster of tube-like feet around their mouth to gather food.
3. To repel predators or when stressed, a sea cucumber might expel their innards or ‘vomit’. And if too much of their innards are expelled, they might die off as a result.
4. The sandfish sea cucumber is the species of sea cucumber which people consume. But they contain toxins, so it must be properly prepared before consumption.

Just a few foot steps, we spotted the third 'discovery', an unknown anemone (picture below).
Discovery Note:
1. Anemones have stinging cells which might harm you if you touch them. So rule of thumb for anemones, don't touch them with your naked hands.

The fourth 'discovery' was spotted by the young 'clown fish' (forgot to get his name, sorry...). A ribbon worm.
Discovery Note:
1. Some can reach a length of 30 meters with a body diameter of only a few millimeters.
2. They seem to have existed on earth for 500 million years.
3. Usually they feed on scavenges and dead animals.

4. A ribbon worm has a proboscis to snap preys. Some are even armed with a piercing stylet that can inject a toxin to their preys.

As the HSBC green volunteers were also conducting a walk for some students on the same morning, we had more available hunter seekers, as a result...

Three knobbly sea stars turned up~ Fifth 'discovery'!

Here's the traditional group photo shot with them (picture below).
Discovery Note:
1. Their name comes from the presence of knobs on their topside.
2. Although they are brightly coloured and covered with knobs and spikes, they are not venomous, so you can touch them!

3. But still, please handle them with care as they are a threaten species.

Sixth 'discovery' had left me wondering for a while on what was it. But after a short contact with my trusty tool, i found out that this was a mushroom coral with its tentacles extended out (picture below).

(Entry @ 28 Dec: This might be a colony of Euphyllia corals instead of Heliofungia) Here's a sunflower mushroom coral which we also saw nearby the mushroom coral (picture below).Discovery Note:
1. Most Mushroom corals do not form colonies like most other corals and most mushroom coral is usually a single polyp.
2. Unlike most corals, most mushroom corals are attached to the reef only when they are small.
3. As larger individuals, they will detach themselves from the reef (if they had attached themselves to the reef) and live loose on the seafloor.

Ron who was the chief hunter seeker of the day then soon found a stonefish sea cucumber (picture below). Seventh 'discovery'. Discovery Note:
1. The stonefish sea cucumber is also known to be harvested for food. But not as popular as the sandfish sea cucumber.

As we 'clown fishes' had explored all the things that were pre-spotted by our hunter seekers, i decided to lead my group near Ron and Luan Keng, just in case , they spotted anything. =p

And they did, a giant clam! Eighth 'discovery'! Prof Leo Tan who was there with all of us on Semakau also then proceeded to give a introduction on the giant clam (picture below).Discovery Note (Addition information from
1. They are the largest living bivalve mollusc and also known as the bear's paw clam

2. They can weigh more than 227 kilograms and measure as much as 1.2 metres across, and have an average lifespan in the wild of 100 years or more.

3. An interesting symbiosis occurs between a unicellular green alga ( Zooanthella ) and the clam. The algae live in the tissues of the clam's siphon and mantle; they are able to obtain the sunlight needed for photosynthesis because the clam lies with its valves opening upward and part of the thick, purple mantle extruding over the shell.

4. In addition, there are crystalloid vesicles on the mantle surface that let in sunlight, thus allowing the algae to live deep within the tissues. The clam uses the algae as a supplementary or perhaps even a major source of food.

Just after Prof Leo finished his introduction on the giant clam, JH brought over a unknown fish which Robert found to check if Prof Leo
could help us to ID it.

According to Prof Leo, this is a 'baby' scorpion fish (picture below). Ninth 'discovery' of the day. Discovery Note:
1. Scorpion fishes have large, heavily ridged and spined heads. Venomous spines on their back and fins with a groove and venom sack. Well camouflaged with tassels, warts and coloured specks.

2. Some scorpion fishes can change their colour to better match their surroundings.

3. Scorpion fishes are not aggressive, but if threatened they will erect their dorsal spines (which is venomous). If danger continues they flee, usually very fast but only for a short distance and then quickly settle back and freeze.

Straying off for a moment, i took a photo of the stag horn coral
(picture below). A favourite.
Tenth and eleventh 'discovery' were nudibranches spotted by Ron. A phyllid nudibranch (picture below) . A marginated glossodoris nudibranch (picture below). Discovery Note:
1. They are sea slugs without a outer shell.
2. They did had a shell when they were young but it slowly disappears as they mature.

And here's a photo of a sponge from a few cm above the sand level (picture below). Twelfth 'discovery'.
Discovery Note:
1. Sponges are simple animals, because they do not have a mouth, gut or other organs nor a brain.

2. But they have a simple body structure which can perform all the functions of an animal.

3. Sponges are sometimes mistaken for corals. For a simple check, take note that sponges have many little holes and few big ones.

4. Sponges have tiny hard, sharp spikes throughout their bodies.

5. These spikes not only provide support but also make them an unpleasant mouthful.

As we slowly walked back towards the shoreline. We suddenly heard a shout from Ron. "Heart Cockle (picture below)". I looked at my group and checked with them if they were interested to check that out.

"Why not".

So here's the thirteenth 'discovery'. =)
Discovery Note:
1. The cockle lives in sand and mud in shallow water.
2. All cockles are hermaphroditic, which means they possess both the male and female sex organs.

Walking near back to the sea grass lagoon, a warty sea cucumber (picture below) laid there waiting for us. Fourteenth 'discovery'. There seem to be a number of sightings of sea cucumbers on this walk.

Discovery Note:
1. Also called the peanutfish, dragonfish or golden sea cucumber in the sea cucumber trade.
2. They supposedly have an unusual defense mechanism where they can become completely limp and eventually disintegrating all together if taken out of the water for too long.
3. However, if they are not done it too much, they have the ability to reverse this process and recover.

As we crossed the seagrass lagoon, another sea cucumber was soon spotted. A synaptid sea cucumber! This was my first time seeing this . Wow~ fifteenth 'discovery'. Discovery Note:
1. It has no tube feet except for highly modified ones that form the oral tentacles.

2. It has a very thin, delicate body wall that feels sticky to touch. The stickiness is not due to mucus or other adhesive, but to other hundreds of tiny, anchor-shaped ossicles located in the skin.

After ending the inter-tidal walk, all visitors were then ushered to the Southern most part of Singapore, which is also the Southern most part of Singapore which the public can have access to (picture below).
Finally, after the land-fill tour and a video presentation by NEA, the trip ended and all of us headed back to main land Singapore for a well-deserved lunch.

And Thanks to all the 'clown fishes' for being such a great group and everyone else on this trip.

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