Monday, July 16, 2007

Hunt & Seek at Semakau on 15 July 2007

Finally, back to Semakau again! We had two very rainy walks last month, but thankfully the weather was superb last Sunday.

This time round, however, my role was different - I was the hunter-seeker!

This was my first time being a hunter-seeker at Semakau. I'm usually the guide. And what made this trip so special was, we started around 5 plus in the morning!

First time doing hunting-seeking, and some more had to do it when it was still dark! That was really quite a challenge.

First of all, how to find my way through the usual route to find the usual stuff when I could hardly see the landmarks? Progress was thus really slow in the beginning, as I had to try to find my way to the usual spots.

Even after finding them, there's another problem - how are the guides going to spot the route markers in the dark?

Fortunately, HSBC was also there conducting a walk, and as they had lots of volunteers, they were able to provide station masters. Thus, for the first few stations, we had station masters manning the stations.

My first task was to find the sand sifting sea stars (Archaster typicus). Many of the sea stars have migrated to the other side of the lagoon, but I was really hoping that I could find it at the usual spot before we cross the seagrass lagoon, so that the guides could talk about the colourful sponges there at the same time.

Was also worried that the sea stars on the other side of the lagoon may be harder to find as they could be some way off the usual route that we took. But luckily, I managed to find several of them just before we enter the seagrass lagoon.

And as it turned out, there were many of them right near the exit of the seagrass lagoon as well. So many of the visitors got to experience them twice.

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. So please remember not to take your time to admire it while holding it in your hand or a dry container!

After crossing the lagoon, the next task was to find the sandfish sea cucumber. This proved to be rather easy as well, as a huge one was right there a short distance in front of us. Apart from the sandfish sea cucumber, thanks to the other guides and HSBC volunteers, we found several other sea cucumbers too!

From top left going clockwise, we had the sandfish sea cucumber (Holothuria scabra), the stonefish sea cucumber (Actinopyga lecanora), the giant synaptid sea cucumber(Family Synaptidae), and the dragonfish sea cucumber (Stichopus horrens). The sandfish, stonefish, and dragonfish sea cucumber are all edible, though they must be properly treated to remove the toxins.

My next task was to find the onch slugs (Onchidium sp.), but as I was making way to the rocks where they were usually found, I saw a trail in the sand. Putting my hand into the sand at the end of the trail, this was what I scooped out.

It's a lovely moon snail (Family Naticidae). Moon snails usually hunt just underneath the sand surface for other little shells. You can see it has a smooth and beautiful shell, as it has a large foot which often wraps around its shell, and thus prevents it from being scratched. I placed the moon snail near the sandfish sea cucumber and moved on to find the onch slugs.

And there they were, feeding on the algae on the rocks. These slugs come out when the tide is low, as they actually breathe air with a simple lung modified from a section of the mantle cavity. The lung opens through a pore alongside the anus at its back end below the mantle.

More closely related to the land snails than the sea slugs, these slugs are thus also called marine pulmonate slugs as they are classified under the Order Pulmonata (in latin, ‘pulmo’ means lung). Most onch slugs hide in air pockets among rocks during high tide, but it was noted that some can also breathe a little through its skin (or mantle) under water. These slugs thus have to remain inactive during high tide so as to survive on that little oxygen they are getting.

Happen to chance upon an article which says that some onch slugs actually follow a mucous trail home after each feeding expedition. Does that mean that if you remove an onch slug from the rocks, then put it back on a different spot, it may not be able to find its way home.. and may... drown when the tide rises??? Oh no... that's a horrifying thought.

Anyway, on to my next target - knobbly sea stars (Protoreaster nodosus).

Found one of them quite quickly, and later one of the HSBC volunteers and one of the guides also found one each. These are among the biggest sea stars that can be found in our waters!

And just when I was setting up the sea star station, one of the NEA staff shouted to me that he found a sea urchin!

Some how he managed to scoop it up without getting free injections. It was a long-spine sea urchin (Diadema setosum). These sea urchins have long, sharp and brittle spines which break easily, so don't handle with bare hands! They normally graze on algae and also scavenge.

Moving on, I found what I think should be a mole mushroom coral (Polyphyllia talpina), which I forgot to take a photo, but you can see it at July's blog. Anyway, here's another type of mushroom coral I found - a sunflower mushroom coral (Heliofungia actiniformis).

Under the mole mushroom coral and most other hard corals, the sunflower mushroom coral is a single living animal, and don't live in a colony.

There were lots of soft corals too, including the omelette leathery soft coral (Sacrophyton sp.) below.

Unlike the mushroom corals which are hard corals, soft corals don't have hard skeletons, but instead, the polyps are connected by a soft tissue mass.

As I seek for interesting things among the corals and other marine life, I noticed that there seem to be lots of little octopuses (Order Octopoda).

I tried many times to catch the ones I saw, and finally managed to get the one above into a pail with help from some of the HSBC volunteers.

And not far from where I caught the octopus, I found one of its distant relative - a fluted giant clam (Tridacna squamosa)!

A giant clam harbours symbiotic algae in its mantle. During day time, the clam spreads out its mantle to allow the algae to receive the sunlight they need to photosynthesize. The clam will then obtain nutrients from the algae.

After finding all these bigger things, I was really hoping to find some of the smaller ones. Found quite a number of the Acanthozoon flatworms, but just couldn't seem to find any nudibranch!

Some how, I think I just need to get the engine to spot nudibranchs started.

Chay Hoon and Juanhui soon found a pustulose phyllid nudibranch (Phyllidiella pustulosa) which they show me. And somehow after this, I started spotting quite a number of nudibranchs too!

I saw several pustulose phyllid nudibranch too (above left) and one marginated glossodoris nudibranch (Glossodoris atromarginata).

The name nudibranch actually means "naked gills", which you can see on the back of the marginated glossodoris nudibranch (the flowery thing). One interesting fact about nudibranchs is that they are simultaneous hermaphrodites, meaning each of them has both male and female reproductive organs. They usually fertilise each other when they mate, though sometimes, one may take on a male role, and the other a female role.

While I was searching for the nudibranchs, I also saw this beautiful anemone. It was quite big, about the size of a huge merten's carpet anemone or magnificient anemone. This is the first time I'm seeing this, so perhaps someone can enlighten me on the species?

Anyway, sea anemones are related to corals and jellyfish. An anemone has stinging cells in its tentacles that can paralyse animals that got too close to it. The animal will then be moved to its mouth in the centre using the tentacles.

Apart from the huge unidentified anemone, we also found a carpet anemone (Stichodactyla sp.)

In a little nearby pool of water was an anemone shrimp (Periclimenes brevicarpalis). it will probably return to the anemone when the tide is higher.

Finally, it was time to go back. While I was cutting across the rubble area, I saw this cute heart cockle (Corculum cardissa).

Unlike most other clams which have their valves flatten like plates, this clam has its opening of the valves cutting across the centre of the 'heart'! It's no wonder that some people collect this shell while it is still alive, kill it and make the shells into little gifts. If the lovers knew how heartless the way their so-called "token of love" was made, will they still see it as a "token of love", I wonder?

All in all, it had been a very good trip with lots of interesting finds. Hopefully I didn't fare too badly playing the role of the hunter-seeker for the first time at Semakau :)


Beach Rover said...

The anemone probably a Heteractis crispa or Macrodactyla doreensis..

tHE tiDE cHAsER said...


JC said...

How big is the squamasa? Read that they can grow up to 16 inches. Look like u guys had fun.

tHE tiDE cHAsER said...

Maybe about 20cm? Have seen larger empty squamosa shells about 30cm wide, but don't think I've seen live ones more than 25cm wide in local waters.

Sursangram said...

Would you have an image of the sea cucumber,Acaudina molpadioides? Am looking for one to show it to my students.
Thank you.