Semakau Field Trip on 18 Oct

Last Saturday, we conducted a training field trip for our volunteers, and my group this time round was Pufferfish.

The tide was horribly wrong when we reach the shore - the coral rubble area should have already been exposed, and it was still under water when we reached! We had to spend quite a bit of time on the upper shore before tide was low enough for us to proceed.

Despite the tide being different from what was stated in the tide table, we fortunately still see a lot of interesting stuff. Here's just a quick listing of some of them.


This is no giant fish scale, but a window pane shell (Family Placunidae). Mind you, it was still very much alive too.


Is the beehoon-like thing next to the gong gong its eggs?


The ocellated sea cucumber (Stichopus ocellatus) is one of the more commonly seen sea cucumber on Semakau. It has lots of 'eyespots' on its top side, which are basically dark papillae surrounded by a lighter ring. Many sea cucumbers have such papillae, which are believed to possess some sensory functions or to help the sea cucumber move around or hold to the substrate.


So is the sandfish sea cucumber (Holothuria scabra). This is the one that you'll usually find in restaurants, but note they must be processed to remove the toxins in them before they can be consumed.


In the seagrass meadow, a synaptid sea cucumber was busy slashing its tentacles around, picking up organic particles to feed on.


Our hunter-seekers found us a very pretty noble volute(Cymbiola nobilis). This snail is a predator of other smaller shells.


Wow! A swimming anemone (Boloceroides mcmurrichi)! Haven't seen one during a guided walk for quite a while. It is able to swim by pulsating its body.


Found this little squid swimming among the seagrasses. The seagrass meadow is an important habitat for little animals, since there are lots of food and hiding places. Anyway, the squid actually changed colour a few times when we were looking at it, probably trying to camouflage itself into the surrounding.


Some of my group members spotted this pair of moon crabs (Ashtoret lunaris). With all their legs being flattened at the tip, it was able to burrow very quickly into the sand, using their legs like spades.


As per usual, there were lots of sand-sifting sea stars (Archaster typicus) after we crossed the seagrass meadow. This is probably one of the most common sea star in Singapore, and can be found on several of of northern and southern islands. We rarely find it on the mainland shores though.


The resident gigantic carpet anemone (Stichodactyla gigantea) was still at the same spot. It had lots of sticky tentacles with stinging cells, ready to sting any little animals that got too close to it.


And just nearby, a little ovum cowrie (Cypraea ovum) was slowly sliding over the rocks. Its smooth and shiny shell was covered by its mantle, which had a dull colour and allowed it to be camouflaged.


Several dragonfish sea cucumbers (Stichopus horrens) were spotted at the coral rubble area and seagrass meadow. Like other sea cucumbers, this one breath through its anus too.


Without a trained pair of eyes, it can be quite difficult to find the hairy crab (Pilumnus vespertilio) among the sand, rocks and dead corals.


Swimming crabs can be identified by the pair of paddle-shaped legs at the rear, which allows them to swim very quickly. The above is probably a blue swimming crab (Thalamita crenata).


A flatworm (Acanthozoon sp.) was creeping over some sargassum when we saw it. And as the name implies, it is really flat! Apart from slithering over the substrate, this flatworm can also swim by flapping the sides of its body.


Some of my group members spotted this little gymnodoris nudibranch (Gymnodoris rubropapulosa). While it looks soft and cute, this sea slug is actually a hunter of other slugs, including others of its kind!


As it got darker, the octopuses also started making their appearances. Octopuses are probably the smartest invertebrates around, and research shows that they can recognise shapes and open jars to search for food.


Fortunately, though the tide was a little high, we still managed to find the fluted giant clam (Tridacna squamosa). This clam has symbiotic algae living in it, which can photosynthesize and pass on some of the nutrients to the former. In return, the clam provide the algae with shelter and also nutrients from its metabolic waste.


On the way back to dry land, we spotted this pretty mosaic crab (Lophozozymus pictor). This is the most poisonous crab in Singapore, and possibly the world, and there has been cases of fatalities from consuming this crab.

Well, it has certainly been a great trip on the whole, despite the higher than expected tide.