Semakau Walk on 29 Jan 2010

Last Friday, we conducted our very first intertidal walk for the year 2010. My group was some students from MGS, and my group name was Flatworm.

The sky was really cloudy when we reached Semakau Landfill, but fortunately, the weather held.


After a tour of the landfill, we proceeded to the intertidal area. Once of the first animals I saw was this Orange Fiddler Crab (Uca vocans). This is a male crab, and it has an enlarged claw. This huge claw is somewhat like a handicap, as it required more resources to maintain, and also made the crab a more obvious target for predators. However, being able to survive with this handicap shows female fiddler crabs that it has the resources and superior genes to produce better offspring. And hence, the females tend to go for males with bigger claws.


Marcus' group found an Elbow Crab (Family Parthenopidae), which got its common name from the way its long claws appear, looking just like bent elbows. It has tiny hair on its exoskeleton which traps sediment, allowing it to blend into the surrounding.


Another crab which traps sediment is this Hairy Crab (Pilumnus vespertilio). This is not the shanghainese hairy crab that's served in restaurants though. In fact, this crab is usually mildly poisonous.


Here's the group crossing the seagrass meadow, a very important habitat with lots of food and hiding places that serves as the nursery ground for many marine animals.


At the edge of the seagrass meadow was this Gigantic Carpet Anemone (Stichodactyla gigantea). It's an animal, and uses its sticky tentacles to sting small animals, which will be brought to its mouth in the middle.


A pair of Anemone Shrimps (Periclimenes brevicarpalis) were found among the tentacles of the anemone. They hide among the stinging tentacles to seek protection from predators. Somehow, they are spared from getting stung by the anemone, as they have a layer of mucus around their body that somehow prevents the anemone from stinging them.


There was also a Sandfish Sea Cucumber (Holothuria scabra) at the edge of the seagrass meadow. This sea cucumber can burrow into the sand to hide from predators, and to seek for tiny organic particles to feed on. It is also the sea cucumber usually served in local restaurants. As they are toxic, they must be properly processed before they can be consumed.


There were hundreds, if not thousands, of Sand-sifting Sea Stars (Archaster typicus) at the sandy area. The colour of the sea star matches the surrounding so well, that it can be rather hard to spot them sometimes, especially when they are in the midst of burrowing.


The Funeral Nudibranch (Jorunna funebris) appear to be in season, as we saw a number of really huge ones. "Nudibranch" means "naked gills", referring to the flower-like gills on the back of most species.


I was quite excited to see that the hunter-seekers have found us the 2 juvenile Cushion Stars (Culcita novaeguineae). We have been seeing them rather regularly during our trips.


Here's the other one we found. Cushion stars are believed to feed on corals.


Since our group name is flatworm, I was really glad to see that our hunter-seekers have found us one Acanthozoon Flatworm (Acanthozoon sp.)! This worm is really flat, making it very fragile. However, being flat has its advantages - this worm can squeeze into very narrow crevices to escape form predator or to seek prey!


As usual, the Knobbly Sea Stars (Protoreaster nodosus) were the highlights of the trip. This sea star got its common name from the knobs on the top surface. It has a calcified armour to protect it from predation also.


And here's the traditional group shot with the knobblies!


Finally, we reached the reef edge and found our resident Fluted Giant Clam (Tridacna squamosa). This huge clam can grow to 40cm across!

At this point, the sky was turning rather dark, and we decided to turn back and head towards the main road. We got up the bus just in time, as it soon started raining!

We were really fortunate that it did not rain earlier, and we still had a great trip with lots of interesting sightings!