25 May 2009

Changi shore: recovering from 'beach improvement'?

Another 2am trip for a super low tide on Changi! While the rest of the shore explorers did the more star-studded stretch of Changi, I decided to head off to another part. I've always meant to check out this tiny stretch of rocks on Changi, but always got there too late (the tide came in already). So this time, I trekked out to START at the rocky area.
It was magical to see a garden of sea fans at the rocky area! The rest of the seagrassy shore was also full of surprises.

This zippy little Spearer mantis shrimp (Harpiosquilla sp.) madly dashed among the seagrasses (as these animals usually do), then suddenly disappeared into the soft silty sand.
Only to pop out again, with just its eyes and antennae sticking out. Quite cute I suppose, unless you happen to be its breakfast wandering by.

Another predator roaming the grassy meadows is the octopus. And this one was trying to drag something into its lair.
It's a crab! I'm not sure if the crab was one that was already dead, or if the octopus had actually killed it earlier.

I have often seen this small purplish octopus in our seagrass areas in the north.
It has a smooth head which I've never seen change texture, and is usually a plain purplish shade. It doesn't make weird patterns on its body.

I also often see this rather large octopus in the seagrass areas in the north. Unlike the small purple one, this one has a large head, compared to its tentacles. But it also has a smooth head and tends to be pale beige with mottles.
The one I saw today was 'walking'! It raised its entire head above the ground and was moving on its tentacles! I've placed both the purplish and beige octopus with smooth heads in one fact sheet. Just for convenience of display. It's hard to distinguish octopus species from a photo.

It was a nice surprise to see this octopus on this shore, my first encounter here.
This one, as you can see, has quite dramatic patterns on its body and its head has 'hairy' textured extensions. And it has two tiny white spots just beneath the large eyes.
It changes its colours rapidly.
And even the texture of its head, here it is with a smooth head! I've seen this octopus commonly on our Southern Islands, and also seen it at Chek Jawa and Pulau Sekudu. But this is my first time seeing the two-spot octopus on Changi.

This snail with spines is rarely seen alive. It too is a predator!
The Rare-spined murex (Murex trapa) eats clams and other snails. It belongs to the same family as the Drills (Family Muricidae) and can also drill a hole in the shell of its victim.

The Frog snail (Bufonaria sp.) is also rarely seen.
It is also a predator, and some species appear appear to feed on tube worms. These have an extendible proboscis and large salivary glands, that are probably used to anaesthetize the worms in their tubes; the worms are then sucked out and swallowed whole. Slurp!!

The Moon snails (Family Naticidae) are fierce predators too, also drilling holes into the shells of snails and clams. Today I saw one that I've not seen before.I tried to take a photo of its operculum (the door that shuts the hole in the shell after the snail retracts into the shell).
But it wouldn't tuck its body into its shell. In fact, it didn't seem to move much at all. Did it just recently die?
I came across a shell of what seems to be a similar snail. The shell is quite thin and rather flat. I have no idea what kind of moon snail it is.

Predators can look harmless and pretty as a flower. Sea anemones are mistaken for vegetables but are actually animals that may kill and eat other animals.
This yet to be identified sea anemone is only commonly seen on Changi. Particularly on this shore. So it was nice to see some of them. It has pretty red tipped bumps on its body column, and its tentacles are banded so it resembles a tiger.

It was a delight to see the Glass anemone (Doflenia sp.).With long transparent tentacles, it looks like it's made of blown glass!
I saw another one with reddish tentacles! Other anemones that were seen include some Haddon's carpet anemones (Stichodactyla haddoni), some smaller carpet anemones that might be Stichodactyla tapetum, some Peachia anemones (Peachia sp.) and of course lots of banded bead anemones on the rocky parts.

Other cnidarians seen on the shores include many Common peacock anemones most with an entourage of Phoronid worms (Phylum Phoronida). The Banded peacock anemones were also present. I only saw one small flowery sea pen (Family Veretellidae).

This fugly fish under a rock sure looks like a predator.
The Toadfish (Family Batrachoididae) has a face only a mother could love. It sulks under rocks to wait for passing morsels which are engulfed in jaws that expand suddenly into a cavernous gape. Prey is usually swallowed whole!

The tiny little Copperband butterflyfish (Chelmon rostratus) has a pointed mouth to suck up small prey.
It was nice to see this little fellow sheltering in a pool to await the incoming tide.

Not all predators are large with big teeth. All marine flatworms are carnivorous. Being absolutely flat, there is no where for their prey to hide. They can slither into any crevice, slide between any shells no matter how tightly clamped.
The one on the left is the Blue-spotted flatworm (cf Pseudoceros indicus) while the one on the right is the Blue lined flatworm (Pseudoceros sp.). There were many of these little worms on the rocks which were encrusted with sponges, ascidians and other sedentary lifeforms.

It was nice to see the Purple-spotted yellow flatworm (Pseudoceros laingensis).
I haven't seen one of these for a while.

Today, I saw lots of brittle stars who were unusually rather listless and did not slink away at the first sign of torchlight.
These three large brittle stars were draped on a brick in the middle of the silty shore. Some were upside down. I have no idea what is happening.
A closer look at the under and upperside suggests they might be the Blue lined brittle star (Ophiothrix lineocaerulea).

I also saw some of these brittle stars with arms that resemble a bottlebrush.
The central disk is thick and star-shaped.
Indeed, these animals are relatives of the more familiar sea stars. Alas, I didn't see any weird sea stars. Just lots of Painted sand stars (Astropecten sp.) and one tiny Biscuit sea star (Goniodiscaster scaber). Other echinoderms include a few Black sea urchins (Temnopleurus sp.) and White sea urchins (Salmacis sp.). There were a lot of Ball sea cucumbers (Phyllophorus sp.) all over the shore as well as many Thorny sea cucumbers (Colochirus quadrangularis) and Pink warty sea cucumbers (Cercodemas anceps).

Among the placid grazers that were plentiful today was the Geographic seahare (Syphonota geographica) and their pink egg strings that resemble a tangle of noodles. Also abundant were Gong-gong (Strombus canarium).

The most amusing find for me today was this odd crab. I observed some movement in a large blob.
It was a small crab attached to a very large thing.
A gentle look and it was a sponge crab (Family Dromiidae). It had decided to use a large living ascidian as a disguise! The ascidian didn't look very happy about it though.
This is what a happy ascidian looks like. I call it the Thumbs up ascidian (Polycarpa sp.) because that's what it looks like when its happy.

What made me really happy today was seeing the garden of sea fans. And also to see that this shore seems to be recovering from 'beach improvement' that I encountered in a visit in Dec 08. At that time, a huge pile of sand had been dumped on the beach. But today, the pile is gone and the nice soft silty shore is back with lush growths of large Spoon seagrasses (Halophila ovalis) and soft shore specialists like the anemones, brittle stars, octopuses and other delightful animals.

While I was out on this shore, Kok Sheng and Chay Hoon and friends were on another having a day full of special echinoderms!

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