Jun 19, 2008

Frogfish on Changi

5am and within minutes of arriving on the shore, Chay Hoon finds a frogfish! Changi is indeed an exciting shore, with marvellous surprises especially if you have keen eyes. Or just lucky to be with Chay Hoon.This rather rotund fish with a woeful expression is probably a Spotted-tail frogfish (Lophiocharon trisignatus) on account of well, the spots on the tail. One thing Chay Hoon and I noticed is that it doesn't have scales. Indeed, it has a loose prickly skin instead.

It also has 'paws'! Its pectoral fins have an 'elbow' and look like hands complete with fingers. Its woebegone expression, helpless waddles and large paws makes it quite an endearing fish.
What is really cool about this fish is that it goes fishing! With a lure!

The lure is at the top of its head and is made up of the first of the three spines of the dorsal fin that is modified into a rod or stalk (called the illicium) tipped with a fleshy, fluffy or otherwise attractive bit (called the esca). This bit is wriggled, jerked and waved about so it appears to be a tasty little morsel. While the fish itself remains motionless and looks just like a lump of rock. Unsuspecting creatures that attempt to eat the lure are instead eaten by the frogfish!

The victim is usually swallowed whole in one gulp of the frogfish's huge mouth. The frogfish can expand its mouth cavity to 12 times its normal resting volume in less than a second, making this one of the fastest capture mechanisms in the animal kingdom.

Chay Hoon remarked that she has been afflicted by frogfishes lately and has been encountering them quite often. Today, alas, she wasn't afflicted with slugs and we didn't see any. And very sorry Kok Sheng, but we saw zero sand stars. And we did look for them.

But we did see several of these white little flatworms with a border of blue spots. They look like living Delftware china. The two different individuals in the photos below were wrapped around something spherical. Could they be eating the blob-like animals? These blobs are ascidians and commonly seen on rocks and hard surfaces.Indeed, flatworms are carnivorous. Immobile encrusting animals are among their prey. The mouth of a flatworm is on the underside of the body, in some, towards the centre or the back end of the body. Being flat, most flatworms most can't 'swallow' their prey. Instead, the pharynx (a part of the gut) is pushed out through the mouth. Either the pharynx engulfs the prey outside the worm's body. Or digestive juices are injected into the prey and the resulting liquefied meal is then sucked up.

Possibly one of these processes was taking place. I don't ever try to pry off flatworms from hard surfaces. They are very delicate and will tear apart if they are touched much less scraped at.

The rocky shores of Changi are particularly teeming with porcelain crabs.With a flat body and pincers, porcelain crabs squeeze into nooks and crannies and shelter under stones. They come in all sizes and scuttle away instantly when they are disturbed.
I saw these really REALLY tiny porcelain crabs, and even what looks like a moult, under a stone. After looking under a stone, be sure to replace it gently the way you found it so you don't crush any tiny animals.

This handsome red porcelain crab is bigger compared to the other little brown ones. It has very long antennae and really large pincers which are richly patterned.
The porcelain crab is not a true crab. True crabs belong to the subgroup Brachyura and have four pairs of walking legs.
Porcelain crabs belong to subgroup Anomura (which includes hermit crabs) and have only three pairs of walking legs. The fourth pair of 'legs' are highly reduced and folded to the sides of the body (you can see the short tabs on this large porcelain crab). Porcelain crabs got their name from their tendency to drop limbs when they are scared. So please don't harass the crabs.

We also explored the soft silty shore which now has a lovely carpet of Spoon seagrasses (Halophila ovalis). There were several fat Geographic seahares (Syphonota geographica) trundling about, with their pink bee-hoon like egg strings here and there.
There were also lots and lots of peacock anemones (Order Ceriantharia). These anemone-like animals are not true anemones. They build tubes to live in and are thus sometimes also called tube anemones.On Changi especially, the peacock anemones often have little black feathery worms with them. These worms belong to Phylum Phoronida and are usually called phoronid worms. I wasn't sure before seeing this, but from the photo above, it looks like the worms are embedded in the tube of the peacock anemone. Do the worms hurt the peacock anemone? I have no idea.Another thing we found out today is that the worm has a very long body column! I posted more information about phoronid worms that were seen at Pasir Ris.

This shore reminds me very much of Dr Daphne the sea anemone expert who visited us last year. Because some of our common sea anemones found there were very interesting to her! This one was apparently new to Dr Daphne and is still yet to be identified. It is quite common on this stretch of Changi. It has yet to be seen on our southern shores. So Changi might be home to some special anemones.There were also lots of swimming anemones (Boloceroides mcmurrichii). These sea anemones actually do swim!
I thought this little sea anemone clinging to a seagrass blade was another swimming anemone.But a closer look revealed a spotted body column (which turned out to be bumps actually).And the tentacles were armed with lot of tiny little bumps which I suspect could be batteries of stingers. I didn't touch it but there was a little cut on my finger and I think something in the water from the anemone made it smart for a while.

I wonder what this anemone is?

There's so much to learn from even this little stretch at Changi.

Unfortunately, this shore is affected by regular dredging at the narrow mouth of Changi Creek.The last round of dredging was in Mar 08, involving some pretty large equipment stirring up the sea bottom and silting up the surrounding water. At that time, a bumboat operator said the earlier dredging did not work because the wake from the passing bumboats washed the sediments back into the channel. So now, they are trying to do something else involving building some sort of wall.

As the sun rose, the tide came in and it was time to go home.How many more sun rises does this shore have before it is 'improved' for beachgoers and other shore users?

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