Jun 5, 2008

Zoanthids of Pulau Hantu

5am and we're back on the shore with Dr James, this time at Pulau Hantu.We find more examples of the zoanthids we saw yesterday at Kusu Island.

There is Palythoa tuberculosa that looks like a rubber mat and coats rocks and rubble. This zoanthid can take on different forms. Some are smooth and unfragmented.
Others are highly fragmented and look almost like pomelo segments! Dr James confirmed that this zoanthid does sometimes purposely break off pieces that are washed away and eventually settle down to start a new colony. It is believed that they mostly reproduce asexually (by division or just expanding the colony). In fact, there are problems in understanding how zoanthids reproduce sexually.
They also come in different colours, some have tinges of other colours such as green.

These zoanthids include sand in their bodies and feel a bit rough to the touch. Dr James elaborated that the sand grains are actually incorporated into the body and not stuck on the outside. Different species of zoanthids may select different sizes of sand grains.

Dr James shares that not every colony of this zoanthid is toxic. Some may have the toxin and others may not. The toxin is being studied for applications in human medicine.

This is another Palythoa species, Palythoa mutuki. Unlike the rubber mat zoanthid, these have more distinct body columns.But they too have a shared base of tissue, as you can see from the close up in the photo on the right. When they are out of water, the tentacles are tucked into the body columm.When submerged, you can see the broad oral disc fringed by short tentacles.
The polyps may be closely packed against one another.And come in different colours. This clump was found near a mangrove tree!

This is a Zoanthus species, those we saw were mostly Zoanthus sansibaricus.These zoanthids don't include sand in their bodies so the surface is smooth to the touch.Here's a closer look at the much smaller polyps.The Zoanthus polyps are also embedded in a common tissue, although this is sometimes hidden by a layer of sand or sediments.

As we looked for zoanthids, we came across other marine life that resembled zoanthids.Zoanthids often crowded next to other kinds of marine life such as sponges, hard and soft corals. This Palythoa tuberculosa is growing next to a brown sponge that, at low tide, looks very much like the zoanthid colony.Here's a close up of the sponge on the left photo, and the zoanthid on the right photo.

The Goniopora hard coral also resembles zoanthids.Its polyps are also a circle of short tentacles on a long body column.But a closer look will reveal the hard skeleton (photo on the left).

Here is another ball of Goniopora hard coral.Another hard coral that looks like zoanthids at first glance is the Galaxea hard coral.A closer look will reveal the hard skeleton that form tall tubes.

And here's a hard coral that looks like Palythoa tuberculosa at first glance.A closer look reveal the hard skeleton that is in the shape of small mounds. The polyps emerge as tiny flowers in the centre of the hard mounds. This hard coral is probably Astreopora sp., a member of the Family Acroporidae.

In the silty sand, there are sometimes tiny sea anemones.That may be mistaken for zoanthids as they grow close to one another. But closer examination will show that they are not connected to one another like zoanthids are.

We also showed Dr James this intriguing colony of animals. I've seen it sometimes on our shores.It's not a zoanthid and Dr James thinks it might be a hydrozoan. Wow! There's really a lot more that we can learn about our common marine life.

As we looked for zoanthids, we also came across many amazing reef animals. Kok Sheng has shared all the spectacular finds on his wonderful creations blog. So I'm just going to highlight a few.

At first mistaken for a mantis shrimp, this creature is a Ghost shrimp (Glypturus sp.)It is very rarely spotted and Dr James says it's a "Hantu Shrimp". Wow, he also speaks Malay. I'm very impressed.

There were lots of fishes in the pools left behind on this very low tide. Including this very pretty filefish.I don't know what kind of filefish it is.

And along the reef edge were these spectacular balls of spines! Diadema sea urchins usually have all black spines. But this has white spines and some spines that are banded!Another one further down had long black spines but short pale spines!Wow, I wonder what they are?

We did quite a long circuit of Pulau Hantu as the tide was very low and long. Pulau Hantu's shores are magnificently alive although they are right next to the major industrial installations on Pulau Bukom and Pulau Busing.

Other blog entries about this trip
Zoanthid hunt at Hantu on Kok Sheng's wonderful creations blog.

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