Aug 1, 2007

Sea anemones of Kusu Island

The Anemone Team is back on the shore, on a clear moonlit morning at Kusu Island! With lots of enthusiastic support from wildfilms and beachfleas as well, we head down to the check out the special anemones on this special island.

The Magnificent anemones (Heteractis magnifica) are indeed well named! They occur in numbers at Kusu.
These large sea anemones with rather fat tentacles and often colourful body columns are homes to False clown anemonefishes (Amphiprion ocellaris). I wasn't patient enough to wait for the fishes to show themselves, but Kok Sheng got lots of photos of these delightful fishes on his wonderful creations blog.

Dr Daphne is reassured to see them again. She was here many MANY MANY years ago (before Independence!) and saw these anemones in numbers on Kusu Island too.

Today, Kusu is still an amazing place both above water and under. See Commensal crazy at Kusu by Juanhui about a recent dive at Kusu.

The Great Carpet Mystery

Dr Daphne confirms that the large sea anemones that look like shaggy rugs that we see on the intertidal are Giant carpet anemones (Stichodactyla gigantea). They are NOT Stichodactyla mertensii, as I had thought all along. Oops.These large carpet anemones are homes to anemonefishes (like the one at Sisters Island) as well as anemone shrimps (like this one above).

Aargh! But how do we tell S. gigantea from S. mertensii?! (I hear you Kok Sheng)

Dr Daphne says anything we see on the intertidal is probably S. gigantea because she hadn't seen a single S. mertensii on all her intertidal trips here. She says S. mertensii tends to settle in deeper water among living corals, and holds its oral disk completely flat against the surface (not in folds).

She says S. gigantea tends to be found in the intertidal among coral rubble (rather than living corals); its oral disk is not held flat, usually in folds. And its tentacles are usually constantly vibrating. She says elsewhere, their tentacles are so sticky that the tentacles will pull off if you touch them. But in Singapore, our S. gigantea doesn't seem to do that (we tried a few times with several). She's not really sure why.

Both S. gigantea and S. mertensii have contrasting bumps on the body column. The bumps can be colourful or not. The body column can be colourful or not. Dr Daphne says for sea anemones, colour and patterns are not a reliable way to distinguish the species as these vary even within species.

The sandy shore of Kusu's lagoon had many of the Giant carpet anemones. Including this rather small one at the mid-water mark!The shore also had several of the more familiar Haddon's carpet anemone (Stichodactyla haddoni). (Which sparked off some really bad "hadn't I told you" jokes). This anemone looks more like short-pile carpet with short, sometimes almost rounded tentacles, often packed so closely together that the anemone appears to have a smooth surface. Its oral disk is also usually fringed on the edge by a pattern of alternating long-and-short tentacles. These anemones are also homes to anemone shrimps.

As we explored the area outside the seawall (only possible at the lowest super low tides), we came across this Snaky sea anemone with fat snaky tentacles.
Dr Daphne confirms this is Macrodactyla doreensis, by looking at the underside which has eye-shaped white dots on the body column. I couldn't take a photo of this as the water got murky.

We also saw lots of the very common Frilly sea anemones (Phymanthus sp.).And the team managed to get some smooth tentacled ones too, so Dr Daphne can make a thorough study to find out whether all the different shapes are indeed different species. She says it could also be that the different shapes and colours could be different stages in the sea anemone's development.

But this is the Anemone Team's Holy Grail: 'Condylactis Not'.
We call this so because it is NOT a Condylactis, which is what I foolishly thought it was. It is a very nervous sea anemone and very difficult to sneak up on and catch for a closer look. We saw four today and got none. Sigh. Photos were taken, but the recovery effort failed. Anemones, after all, are not as helpless as they might first appear. Even four highly evolved beings find it difficult to catch one.

Dr Daphne also found a whole bunch of sea anemones high up on the seawall. They don't look like much all tucked up and blob-like. And I probably will never get to see what they look like underwater as by the time they are submerged, it's high tide! That's how high up they were. These anemones are quite tough indeed!

The reefs also have anemone look-alikes to confuse the Anemone hunter.These are zoanthids or colonial anemones (Order Zonathinaria). They are NOT true anemones, although Dr Daphne looks carefully and finds one or two true anemones in this packed crowd of non-anemones!!

There are also fluffy, feathery things that might at first glance appear to be sea anemones.The bluish feathery creature is some sort of soft coral. It is also sometimes brownish (like the smaller clump in the centre). The yellowish clump is another kind of soft coral.

In the second lagoon, there were lots of small feathery creatures too. These are fanworms!The animal looks like a segmented worm and lives in a tube. But unlike other icky worms, it has on its head a flamboyant ring of fine feathery tentacles, like a cabaret dancer!

As usual, despite best attempts to focus on them 'nems, we come across some other special creatures. For me, it was this pretty moon snail that I've also seen on Changi as well as at Pulau Semakau. It seems to like seagrass areas. It has a pretty pink front portion, and the foot has a white lacy pattern.

Yuchen found these amazing nudibranchs that I've never seen before.Some nudibranchs can drop off parts of their body if they are scared. That's probably why there seems to be parts missing of this nudibranch. Well just have to wait for Chay Hoon or Ron to tell us what this slug is.

As we were just about to go home, I finally found the teeny TINY sea anemones that I remember seeing at Kusu before.They are minute white specks. Of course, the first time I 'found' them was when I got home and enlarged a photo I took of a shrimp and realised that it was surrounded by tiny stars in the seagrass!
They are really very small, and I spent all morning trying to find them. Dr Daphne has very sharp eyes and notices there are brown ones as well as white one! Wow!

We've sure seen a lot of sea anemones and learnt so much from Dr Daphne. Tomorrow, one last day out for the Anemone Hunt!



Hmmm...The nudi looks like platydoris scabra

tHE tiDE cHAsER said...

Sure looks like Platydoris scabra. Have seen it at Semakau as well :)

Here's a photo of the one I've seen. A bit out of focus though. Pai seh :P

ria said...

Wow! Thanks Slug Experts! It was quite a special slug indeed.