Saturday, December 10, 2011

Feather stars and commensals at Little Sisters

One of the reasons that make me look forward to visiting Little Sisters Island is definitely the numerous feather stars that can be found on their reef.

I visited the smaller of the two Sisters Islands about two weeks ago and had a great time looking at the different kinds of feather stars.

Inspired by the previous trip at Beting Bronok where we found strange commensals on the Feather stars (Order Comatulida), James and I spent more than an hour to closely observe what else can we find living on feather stars. Indeed there are creatures found living on the arms of this particular feather star!

Can you see the banded-looking organisms found attached to the arms of the feather star?

These organisms seem to be rather well camouflaged against the lines found on the arms.

James later found an even smaller crinoid / feather star! And there is also something living on it as well!

Here is a closer look at the brown spot.

According to James' blog, these commensals are actually worms. They are likely to be Myzostomida, obligate symbionts of echinoderms (very commonly crinoids). Myzostomida come in a few types, some reside in their hosts while others cling to the outside. 

The external ones can be further separated into those that move about freely on their hosts, those that sit mainly at the disc of the crinoid, and elongate ones which cling to and move along the crinoid arms and pinnules.

The most common type of feather stars found on the reefs of Little Sisters Island is the bright red type. Here's showing you a collage of 4 different red feather stars in a sequential closing of arms position.

Among these red feather stars, we also found more living stuffs such as this unknown organism.

There was even a tiny colourful brittle star (Ophiothela danae)!

More feather star photos! This is a juvenile red feather star.

And I'll end off the series of feather star photos with this gorgeous black, brown and white feather star!

Some parts of the reef at Little Sisters are crowded with life and full of different colours. You can find sponges, soft corals, hard corals and zoanthids in this garden.

There were also several Barrel sponges (Xestospongia testudinaria) on the shore.

At first, I thought this was a weird hard coral but it is soft to the touch. Is it some kind of sponge or soft coral or ascidian? Hmmmm...

It was kind of difficult to photograph these black Cave coral (Tubastrea sp.) as there always seem to be some kind of reflection in the water. Otherwise because of the black coloration, one can easily observe silt floating near the coral.

After struggling a bit with my DSLR camera and with the constant crashes of the waves, I managed to get feeble shots of the black cave corals with their tentacles extended.

It was difficult to do that for the orange cave corals as they usual are found at deeper and darker corners of the reef. So I used my underwater camera to take pretty shots of these corals.

We saw quite a number of slugs such as this Ornate leaf slug (Elysia ornata) found among the seaweed.

This Pimply phyllid nudibranch (Phyllidiella pustulosa) is rather common on our southern shores.

As usual, Chay Hoon lives up to her name and found this unknown tiny slug that is definitely less than 1cm long.

Ria showed me her finds of what looks like the China moon snails (Natica onca) which we have only seen at Cyrene Reef previously.

We ended the reef walk with this find of the Land hermit crab (Coenobita sp.) at the high shores.

It is definitely a blessing to have rain-free trips for the 3 consecutive trips during that week. Thank God for that! :-)

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