Monday, October 01, 2007

Pulau Semakau - 29th & 30th Sept 2007

During the year end in Singapore, the low tide are occurring during the evening time instead of early morning during the early half of the year.

This weekend, I was at Pulau Semakau for both consecutive days for the walk (my OJT). Was assigned to Samson's (Sat) & Ron's (Sun) group.

For those who are wondering how do we get to Pulau Semakau since it is the furthest south of Singapore where general public can visit. We boarded on a fast boat like the one shown below at Marina South Jetty and it take ~30mins to reach. Doesn't it look like those Police fast craft? :P
As per normal, part of the trip to Pulau Semakau always includes the Landfill tour. No exception this time.

Can you spot the Central Business District? :D

After the Landfill tour, we proceed to the intertidal wetland for the guided walk. While reaching the mud/mangrove area, we saw lots of small hermit crabs gathering together. Most likely they have gathered to change out their shell. I wonder if these hermit crabs still perform the ‘shell fights’ during such mass gathering.
While still at the mangrove area, nearby there is a mangrove tree. Under the shade of this tree, there are yet anther mass gathering of crabs. This time round, its the Fidders Crabs (most likely the Orange fiddler, Uca vocans. Many of the males (with large claws) are actively waving their claws in an attempt to attract the female crabs.

Our hunter seeker for Saturday had a great find, A Moon Crab. Moon Crab normally burrow just below the surface during the day and will only forage for small shellfish, worms and other animals at night. Thus the reason why we hardly see them during morning low tide walk. Even the evening walk are rare.

During this weekend, we will able to spot 3 different species of Sea Cucumber. Below is the sandfish Sea Cucumber. Sea cucumbers are echinoderms—like starfish and sea urchins. They feed on tiny particles like algae, minute aquatic animals, or waste materials. When threatened, can discharge sticky threads to ensnare their enemies while some even go to the extend of mutilating their own bodies as a defense mechanism by jettison some of their internal organs out of their anus. Luckily the missing body parts are quickly regenerated.
Another interesting find on Saturday, a marine Fireworm. A fireworm is a type of bristleworm. It can grow up to 30cm in length. This worm has groups of white bristles along its side. The bristles are hollow, venom-filled setae which easily penetrate the flesh and break off if they are been handled. IT will result in intense irritation in the area of contact, hence the common name.
Marine Snails are very common in any marine habitat. They belong to the class gastropoda which includes the sea slugs. Below is a whelk snails with an Anemone on it shell. They reminded me of the "PomPom Crab"which has small anemone on its pincher. This relationship between 2 different species living together is known as Symbiosis. Symbiosis has 4 general kinds;
- Mutualism where both species benefits.
- Commensalism where only one species benefit while the other is unaffected.
- Parasitism where only one species benefit while the other is harmed.
- Neutralism where neither species benefit nor harmed.

For this case, it could be either Mutualism or Commensalism since the anemone might just be taking a free ride to food source (Commensalism). However, the anemone could also be helping to protect the snails from prey as it can sting (Mutualism).
We also spotted a few other species from the class gastropoda like the Volute and Sea slug (unfortuntely was not able to get a pix of it). This particular Volute is laying eggs. Can you see the formation of its eggs?

There is also a spotting of flatworm. Flatworm are not related to sea slugs or other molluscs although it look very similar to a sea slug without the exposed gills. Flatworm are active carnivores and scavengers and are commonly found feeding on dead, injured animals, colonial animals and soft-coral.One of the highlight of the walk, the Octopus. Octopuses have eight arms (not tentacles) with suction cups. They also have a beak located in their mouth, similar to those found on birds, which they use to kill their prey and bite them into pieces. Octopuses are highly intelligent, probably more intelligent than any other order of invertebrates. It has been doucmented before that a Octopus is able to open a screwed bottle cap to hunt for its prey.
Whenever we are on the inter tidal area, we can always hear some clipping/clapping sounds around us. These sounds are actually made by the Snapping Shrimp. The snapping shrimp produces these loud snapping sound by an extremely rapid closure of its snapper claw. It previously commonly believed that the sound is generated when the two claw surfaces hit each other.

Pulau Semakau is one of the inter tidal area in Singapore where we can find lots of corals, both hard and soft. Below is one the Long Tentacle Mushroom Coral, most likely a Heliofungia.
Beside corals that have colony of animals living together. There are also Zoanthids which are commonly known as button polyps or colonial anemones. Zoanthids are radially symmetrical and are made up of two basic tissue layers and possess salient "stinging" cells. Their body cavity formed by the tissue layers bears series of tentacles around a single body/mouth/"anus" opening/mouth.
All in all, it has been a fruitful weekend. Saw a number of new things that I have not seen before. Sadly got to wait till year for the next trip. Just how lovely is the sunset there......