Saturday, September 29, 2007

Semakau Walk with Dunman High

This evening we finally had our very first evening walk at Semakau Landfill for the season! It's certainly great that I didn't have to wake up like 4 or 5 am in the morning for a change :)

I had a group of enthusiastic Sec 4 girls with me from Dunman High. Our group name was supposed to be mudskipper initially, but Luan Keng decided to change it to clownfish instead.

I was thinking, shucks, seemed unlikely that we would see the animal that gave us our group name this time round. I was pretty sure that I would have better chances finding a mudskipper rather than a clownfish.

True enough, one of the first animals we saw was this mudskipper (Family Gobiidae). While they could stay out of water, mudskippers are not amphibians, but fish! So how do they manage to stay out of water then? Like the way we carry an air tank when we go for scuba diving, they carry "water tanks" instead. The "water tanks" I'm referring to are their gill chambers and mouth. Mudskippers thus can't stay too far from water so that when the oxygen in the "water tanks" run out, they can replace the used water with fresh sea water.

Thought this was a rather cute photo and thus decided to snap it :)

We were keeping really still, waiting for the fiddler crabs (Uca sp.) to come out of their holes.

Near the crab holes, I found this little land hermit crab (Coenobita cavipes). Unlike the crabs that we normally eat, hermit crabs are not true crabs, and have a soft abdomen. Thus, they need to find shells to tuck their butts in for protection. So if you are out there on the shores, please don't pick up any shells, or you may be depriving some hermit crabs of their protective shells, and they will have to run around naked! That makes them very vulnerable to predators.

Talking about hermit crabs always reminds me of pet shops selling them as pets. These pet hermit crabs are collected from the wild, and Singapore alone imported thousands and thousands of them every years! Imagine if these goes on, they may actually be gone from the wild in future at their places of origin! While I have no issue with people keeping pets, I certainly hope that the sales of pets collected from the wild should be minimised, if not prohibited, because it will severely affect the ecosystem, and drive a wild species to extinction!

We also saw a number of living sea snails (meaning, with no hermit crab attached, at least while they are alive...). On the left is a spiral melongena (Pugilina cochlidium). There was a clam attached to its foot. Could it be feeding on it? Hmm... On the right is a noble volute (Cymbiola nobilis) laying eggs! It's always encouraging to see animals feeding and reproducing, because that just shows that our shores are very much alive!

Before we crossed the sea grass lagoon, we also saw several sand-sifting sea stars (Archaster typicus). Sea stars move around on their little tube feet. As a sea star uses sea water to support its body and move its little tube feet, it is thus very stressful for them if you take them out of sea water for too long. Amazingly, if a sea star loses its arms to a predator, it can actually regenerate it, as long as the central disc is not damaged.

And here's a group shot of my group crossing the seagrass lagoon! Seagrasses are like the forests in the sea! While many animals live in the forest on land, many sea creatures live among the seagrasses because there are lots of food and hiding places there. That makes it an excellent nursery ground for many animals too! Do you know that many of the fishes that were served on our dining tables live at least part of their lives among seagrasses?

As we walk on, we encountered several species of sea cucumbers. From top-right clockwise, we have the dragonfish (Stichopus horrens), sandfish (Holothuria scabra), a synaptid sea cucumber (Family Synaptidae) and ocellated sea cucumber (Stichopus ocellatus).

Sea cucumbers are made of a tissue called catch connective tissue which allow them to keep their body soft when they are moving around, but yet in an instance, they can turn rock hard to protect themselves when they feel threatened. And do you know that a sea cucumber actually breathes through its anus?

Along the way, we also saw a gigantic carpet anemone (Stichodactyla gigantea). An anemone is actually an animal! It has a mouth in the middle, and it has stinging tentacles to paralyse little fish and other animals that get close to it. Now, will we find a nemo among the tentacles?

And YES we did! The clownfish group managed to spot a tiny clownfish! Can you see it some where near the middle? Sorry for the poor quality of the photo, but I could not spend too much time trying to get a good photo like my other non-guiding trips. This is actually an ocellated clownfish (Amphiprion ocellaris). Actually, it is not really the same species as the one you see in "Finding Nemo", but a close relative.

Semakau was a great place to see corals, and we saw lots of beautiful hard corals. On top, we have the corals that live alone, a mushroom coral (Fungia sp.) on the left and a sunflower mushroom coral (Heliofungia actiniformis) on the right. At the bottom, we have the ones that live in a colony. Think of each huge coral like an apartment building, and each hole on the coral has a little coral animal (also known as a polyp). And these animals build their apartment themselves with calcium carbonate, unlike most of us who need other people using machines to build our houses for us! On the left, we have a boulder coral (probably Favia sp.), and the other is an anemone coral (Goniopora sp.). Each little flower-like thing is a polyp!

Semakau also has huge patches of soft corals. On the left is what we called the dead men's fingers (Sinularia sp.), and on the right is the omelette leathery soft coral (Sacrophyton sp.) These corals have lots of little polyps living together in a shared leathery tissue.

Our hunter-seekers were really good today, and they found many interesting animals for us, including the colourful flatworms (Pseudoceros sp.) on the left and the little octopus (Order Octopoda) on the right. A flatworm has a very simple but well-defined brain, and several studies have been conducted on some species to better understand how brains work! The octopus, on the other hand, is believed to be the brainiest invertebrates! Experiments have shown that they can be trained to distinguish between different shapes and patterns.

This piece of dirt-like thing is no dirt, but a little seahorse (Hippocampus sp.)! I've seen seahorses many times, but I still get excited whenever I see one. Imagine this little seahorse hiding among seaweeds covered with silt - it will be almost impossible to spot! What a master of camouflage!

Our hunter-seekers also found us a blue-spotted fantail ray (Taeniura lymma). These rays have a spine on their tails, which can easily puncture your skin and inject venom inside, causing great pain. So when you are out there on the shores, do watch your step, because these rays often hide under the sand and will give you a nasty jab if you accidentally step onto them!

At this point in time, it was turning dark, and we had to head back soon. I quickly brought my group to yet another of my favourite animals.

This is a fluted giant clam (Tridacna squamosa)! These huge clams have tiny little algae living in them. The clam will provide carbon dioxide for the algae, while the latter will photosynthesise when there is sunlight, and provide oxygen and food for the clam.

It was really unfortunate that it was turning quite dark already, and we had to head back. There are still so many things to see! Actually, even though I have been to Semakau Landfill so many times, there are still many places which I haven't explored yet. Semakau Landfill is just too big to be explored within a few days, and we still see new things every now and then!

In fact, the best way to explore it is probably to become a nature guide, and I do hope some of the visitors in my group today will be keen to become nature guides in future :)

Updates:My DHS visitors have sent me the group photos!

Here's my group - Clownfish!

And here are all the participants from DHS!

See also:
- July's entry at his Where Discovery Begins blog.
- Kah Chine, our hunter-seeker's entry at her Walking Loka blog.

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