Semakau Inter-Tidal walk on 5 July 2008

Sixty Seventh Discovery Posting:

Over the mornings of the past weekend, I was over at Semakau land-fill island for another weekend of inter-tidal walks. And on Sat (5 July), I was guiding the group, Noble Volutes.

And the first 'discovery' of the morning was a group of common sea stars (picture below).
Discovery Note:
1. Their tube feet are interesting as they are used for walking, handle food as well as breathing, and probably to catch prey as well, talk about multi purpose!
2. Sea stars get stressed when out of water, this is because while we have blood circulating our bodies, they have sea water circulating their bodies.
3. They are not as common as their name suggests. This is due to past over-collection and habitat lost past and present. So don't take them away from their homes when you see them. =)
4. Some sea stars are predators that prey on worms, crustaceans and bivalves while some are known to eat decayed plant matters.
5. Many sea stars eat with their stomach outside their body. When doing this, their tube feet will pull the two shells of a bivalve apart. And while still attached to their prey’s body, they extend their stomach out through their mouths into the bivalve shell.

As the sunrise was really nice, I decided to take a Volute group photo with the sunrise as the background (picture below).

And very soon, Volutes got to meet one of their own kind, and it was laying eggs! Second 'discovery' (picture below)!

Discovery Note:
1. Volutes are carnivorous.
2. They prey on bivalves, enveloping the victim completely with their foot forcing the bivalve to finally open from exhaustion and lack of oxygen.
3. They can grow to more than 20cm and used to be common but now threaten due to 'harvesting' from humans and habitat lost.

Not far away, the third 'discovery', Volutes got to see another kind of sea snail laying eggs, a spiral melongena (picture below).
Discovery Note:
1. They seem to like to lay eggs on hard surfaces.
2. Each "petal" is one egg capsule.

It was also kinda of like a sea slug day, as we saw a few types of nudibranches, here's one kind which is not so commonly seen at Semakau, a platydoris nudibranch (Platydoris scabra), fourth 'discovery' (picture below).
Discovery Note:
1. 'Nudibranch' means 'naked gills'. The name comes from the flower-like gills found on the back of many nudibranchs. These nudibranchs use the gills to breathe.
2. Nudibranchs are related to snails. Little baby nudibranchs are born with shells, but they lose them when they become adults.
3. Most nudibranchs are carnivores, they eat immobile or small, slow-moving prey. Examples are sponges, ascidians, hard corals, soft corals, sea anemones etc. This particular nudibranch feeds on sponges if my memory serves me correct.

Fifth 'discovery' were two different kinds of mushroom corals (pictures below). Discovery Note:
1. Most mushroom corals do not form colonies like most other corals and some mushroom coral is usually made up of a single polyp (The ones shown above probably are).
2. Unlike most corals, most mushroom corals are attached to the reef/rocks only when they are small.
3. As larger individuals, they will detach themselves from the reef/rocks (if they had attached themselves to the reef) and live loose on the seafloor.

And just almost next to the mushroom corals, we spotted a sandfish sea cucumber or also known as garlic bread sea cucumber, sixth 'discovery' (picture below).

Discovery Note:
1. The popular Chinese name for sea cucumber is haishen, which means, roughly, ginseng of the sea.
2. They have a soft, wormlike body and can range from a few centimeters to even 90 centimeters in length!
3. To repel predators or when stressed, a sea cucumber might expel their innards or ‘vomit’. And if too much of their innards are expelled, they might die off as a result.
4. This particular species of sea cucumber is commonly harvested for food for the Chinese, but this has to properly processed before any consumption, as it is mildly poisonous.

And the star highlight of the walks would have to be the knobbly sea star, our hunter seekers (HW and LK) found us two today (picture below)! Btw, this is the seventh 'discovery'. Discovery Note:
1. They get their name from the knobs they have.
2. Although most of them are mostly red or orange in colour, beige or brown coloured knobbly sea stars have been spotted before also.
3. I have heard that they feed on lots of different things, I wonder if anyone knows what's their actual diet? A good topic for study probably, haha =P
4. Can you believe that a knobbly seastar might be larger than your face? It’s about 30cm across! (look at the picture below to get an idea)

Of course, a traditional group shot with the stars (a pun here probably?). And the last but not least eighth 'discovery', a sea urchin (picture below)! Discovery Note:
1. Upon first look, you might think that a sea urchin is sessile (incapable of moving), but this is not so, they actually use all the pointed tips to move around.
2. The pointed tips are actually spines connected to their skeletons.
3. Some sea urchins have venomous spines, so just to play safe, it is advised not to come into contact with the spines of any sea urchins.
4. The orange dot which you can see (picture above) is actually is anus, it's mouth (claw-like) is located on its underside.
5. Sea urchins belong to the same phylum of animals as the sea stars and sea cucumber, so they have no brains!
6. Their diet consists of plant and animal matter, including kelp, decaying matter, algae, dead fishes, sponges, mussels, and barnacles.
7. Click here to read more about sea urchins on the Chek Jawa guidebook, which is available online.

Finally, a look at the beautiful corals on Semakau (picture below). Thanks to all Volutes who made this trip another enjoyable trip despite I having to wake up around 330am in the morning =P.