08 July 2009

Nem check at Changi

We're back on one of our favourite stretches of Changi early this morning under a full moon.
In the murky outgoing tide, there are lots of marine creatures. But today, I'm trying to check up on the sea anemone situation here.

There are lots of these fat sausage shaped anemones with cylindrical body columns and short slender tentacles. I've so far only seen these anemones on this part of Changi.
Usually, they are stuck on a shell occupied by a hermit crab, like this one seen on a trip last year. The sea anemone is often many times bigger than the hermit crab! But today most of these anemones were stuck to rocks and litter. While many of the hermits were truddling around on the shore without anemones on their shells.
I could only manage a partial shot of the oral disk of this one. It has pretty white stripes!
I have no idea what these anemones are. I'm sure Dr Daphne will help sort these and our other anemones out.

The usual anemone favourites were seen on the shore. Several of these tiger anemones with short, banded tentacles and a pair of maroon spots on the oral disk. The body column has lots of little bumps with a red spot.
As well as lots of these small anemones found in sandy places with stripes on their tentacles. Some have elaborate patterns on the oral disk.
Others are plain. Are they the same kind of anemone?
I saw one medium-sized Haddon's carpet anemone (Stichodactyla haddoni) and one tiny carpet anemone (may be Stichodactyla tapetum).
And also one swimming anemone (Boloceroides mcmurrichii). This animal can actually swim! It is basically a ball of many tentacles with a very short 'foot'. You can hardly see its mouth for all the tentacles.
And I saw this intriguing blob again. I have no idea what it is.
Among the large boulders were lines of blobs. These are little anemones that live in high places, probably the banded bead anemones.
It's tricky to look for anemones because there are other animals on the shore that are easily mistaken for them. In the photo on the left is a Peacock anemones (Order Ceriantharia) which is NOT a true anemone (Order Actiniaria). Peacock anemones live in tubes. In the photo on the right is a flowery sea pen (Family Veretillidae).
And everywhere in the murky waters and in pools were these branched tentacles that look very much like sea anemones. They are actually the feeding tentacles of buried sea cucumbers, probably the Ball sea cucumber (Phyllophorus sp.).
Here's more on how to tell apart animals with a ring of smooth tentacles and a photo index of blobs you might see on our shores.

In the quest for nems, I of course chanced on many other marine creatures. There was this really enormous blob which is a moon snail (Family Naticidae). It has a body that seems to be much larger than its shell! It was the size of my palm and the snail refused to retract into its shell so I couldn't see its shell structure.
And here's a pretty little shell! It looks like it was a baby Bailer volute (Melo melo). The shell is now put to good use by a small hermit crab.
Indeed, nothing is wasted on the shore. Empty shells are in great demand by hermit crabs who need to 'upgrade' as they grow bigger, or when their borrowed shells are damaged.

Here is a queue of patient hermit crabs clustered around what seems to be a recently demised snail. While a crowd of busy little whelks are cleaning out the previous occupant of the shell, the hermit crabs cling onto the shell.
These Common whelks (Nassarius livescens) sure were busy on the shore today. A whole bunch of them were hustling to get to this dead crab. The whelk's all-you-can-eat breakfast buffet has attracted them from far and wide, it seems. The seagrasses seemed to be doing well, looking lush and green. There were also some black sea urchins (Temnopleurus sp.) on the shore. While I checked out this part of the shore, the others were seeing stars at another part!

I also visited the rockier part of the shore which seemed oddly quiet. Hardly any sponges, and only one Crown sea star (Asterina coronata), although there were many patches of Zebra hard corals (Oulastrea crispata).

I said hello to a guy who was walking out into the water with a cast net. He said he was looking for crabs and prawns. There was a great deal of litter on the shore, and someone had dug two enormous holes in the middle of the seagrass area, possibly to look for worms.

Other posts about this trip
Changi beach - Checking every peacock anemone by James on his Singapore Nature blog

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