Jul 30, 2007

Sea anemones of Changi

Another early morning trip with the Sea Anemone Team. We're back on Changi!

Dr Daphne is reassured to see the large Haddon's carpet anemones (Stichodactyla haddoni), some of them with anemone shrimps!We also saw several of the much smaller Stichodactyla tapetum. We had always thought they were merely baby carpet anemones. Dr Daphne says they are in fact a separate species!They can be quite tiny, a little bigger than a seagrass leaf. And don't grow much bigger than the length of about 4-5 seagrass leaves across.

We also saw more of the 'strawberry' sea anemone (because it looks like a strawberry when its tentacles are tucked into its body column). This one was expanded. It has a pair of maroon spots near the mouth, not so obvious in this photo. Dr Daphne is already familiar with this sea anemone and we leave them alone.

Among the first-time encounters was this large plain sea anemone without any markings.Dr Daphne thinks it might be similar to one that we saw at Sisters Island a few mornings ago. But she'll have to have a closer look.

We are also eager to show Dr Daphne the sea anemones found on the shells of hermit crabs. It is only on Changi that I've noticed that lots of hermit crabs have sea anemones on their shells. There are usually lots of hermit crabs. Alas, today, we could only find this one large hermit crab, with a small sea anemone on it.

Dr Daphne shared that one of her colleagues observed in a tank that when an octopus was introduced into the tank, all the hermit crabs soon transferred sea anemones onto their shells. Without the octopus, the hermit crabs left the sea anemones alone.

When a hermit crab changes to a new shell, it may also transfer the sea anemones to the new shell.

Dr Daphne was also very interested in the tiny sea anemones found on whelk snails (Family Nassaridae). Whelks are scavenging snails with long 'noses' to 'sniff' out the recent dead. They can move quite fast once they get a whiff of a delectable carcass.

Many of the whelks on Changi had a tiny hitchhiking sea anemones on their shell. The sea anemone can be quite large compared to the size of the snail. It has pretty stripes.
I wondered how the sea anemone could 'find' the snail, and certainly the snail can't 'put on' a sea anemone the way a hermit crab does. The snail doesn't have pincers. Dr Daphne says this is one of the wonders of nature, that tiny sea anemone larvae can settle onto the correct place in order to grow up into a mature sea anemone. Often, the larvae are attracted to the snail by the chemicals that the snail produces.

Chay Hoon also found a brown blob (no photo, sorry). When we took a closer look at it out of the sand, it was very strange indeed! Dr Daphne is intrigued and will take a closer look at it in the lab.

We also saw lots and lots of Peachia sp. and left them all alone. Having properly looked for sea anemones, we now realise these sea anemones are quite common indeed.

And finally, after many back-breaking attempts to find them, Yu Chen finds the tiny seagrass anemones!
They are really tiny and he literally crawls on the sand to find them! Way to go YC!

Other sea anemone facts we learned today: Chay Hoon went diving at Hantu yesterday (immediately after the sea anemone hunt, she's amazing), and saw what looked like a sea anemone on a sea whip. We all thought she was mistaken, but Dr Daphne says this is quite possible!

We also wondered whether any sea anemones were parasites. Dr Daphne says the seagrass anemones above can be considered parasites. As larvae, they eat up the gonads (reproductive organs) of jellyfishes. When the jellyfish swims over seagrasses, the larvae drop off and settle on the seagrass and turn into adult sea anemones. Gross!

This stretch of Changi is very rich. There were lots of busy moon snails, which have smooth white bodies much larger than their shells. These white blobs were often mistaken for sea anemone blobs! To the frustration of the Anemone Hunters.

Among the seagrasses was also this rather large scallop.And another commonly encountered animal on this shore, the cuttlefish.There were also lots of moon crabs, including this pair that looked like they were up to making baby crabs.Another satisfying Anemone Hunt. And good weather too. We are convinced it is Dr Daphne that is holding the wet weather at bay.

Let's hope our luck holds for the trip tomorrow!

1 comment:

Anonymous said...

i think sea anemones r coooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooollllllllll NOOOOOTTTTTTTTTTT