26 April 2009

Short sunrise at Sekudu

Pulau Sekudu lies just off Chek Jawa on Pulau Ubin. Our last visit to this fascinating island was in Jul 08!
So we are anxious to see how it is doing, despite a 2am wake-up call.

There's a bloom of Sea lettuce (Ulva sp.) a green seaweed that seasonally occurs in large quantities. A soft carpet of the seaweed encircles the low water mark.
This is not necessarily a bad thing as the seaweeds provide food and shelter for a wide variety of creatures. There were lots of peacock anemones, some flowery sea pens, plenty of tiny crabs and shrimps and a wide variety of fishes. In fact, so many fishes that I've done a separate post about them.
And among the first things I come across are lots of White sea urchins (Salmacis sp.). They were large but often buried under seaweeds or camouflaged by the bits and pieces that they carry.
There were also a few Thorny sea urchins (Prionocidaris sp.) and Black sea urchins (Temnopleurus sp.). They were also well hidden among the seaweeds. We all tried to stay on sandy patches to avoid crushing these delicate animals.

Later on, I found out that the rest of the team also spotted the Pink sand dollar (Peronella lesueuri) which so far we've only seen on Pulau Sekudu. And Chay Hoon found a heart urchin!

Pulau Sekudu is a great place to encounter other echinoderms.
There were lots of Sand stars (Astropecten sp.). Both the ones with colourful designs, and the plain ones. Although generally found in sandy places, they were quite plentiful this morning among the seaweeds.As well as Cake sea stars (Anthenea aspera) of various colours and designs.And I saw a huge one! Here is the tip of my bootie (Size 7) for comparison.Another monstrous sea star was the Eight-armed sand star (Luidia maculata). This carnivorous star looks like it's searching among the seaweeds for something to eat! It only had six arms though. From the underside, it's clear it never had 8 arms. Hmm. Another thing I noticed was that the tube feet at the tips of the arms are long and skinny, unlike the club-tipped thick tube feet elsewhere along the arms.
Later on, I came across another Luidia maculata half buried in the sand. It too had only six arms and also lost tips of its arms. Unlike in the earlier sea star which was regenerating its broken arms, this one has yet to do so. It is important to remember that while sea stars can regenerate broken arms, they do so slowly. Meanwhile, they are disadvantaged. So please don't handle sea stars as they can purposely drop off an arm if they are stressed.

Chay Hoon also saw the Red scaly sea star (Nepanthia sp.)!

A relative of the sea star is the brittle star.And many were seen today. The one I saw only had its arms sticking out of the coral rubble, while its central disk was well hidden away. Often mistaken for bristleworms, the arms are flexible and have lots of spines. This one is probably the Blue-lined brittle star (Ophiothrix lineocaerulea) from the pattern on the arms.

Compared to their more attractive echinoderm relatives, sea cucumber are often ignored.It was great to see the Orange sea cucumber (which sometimes has blue stripes) and the Beige sea cucumber that looks like it's covered in sand. I still don't know what these sea cucumbers are. I also saw a Garlic bread sea cucumber (Holothuria scabra) and several Ball sea cucumbers (Phyllophorus sp.)

There were also lots of the large Haddon's carpet anemones (Stichodacylat haddoni). They were doing fine, all looking normal.
I also saw something that might be the Tiny carpet anemone (Stichodactyla tapetum) (photo on the right). It looks like a miniature of the much bigger carpet anemone species.There were also Swimming anemones (Boloceroides mcmurrichii) which actually CAN swim. As well as the anemone in the photo on the right which I don't see often.

Of course there were lots of crabs. Swimming crabs large and tiny (Family Portunidae) and large Stone crabs (Myomenippe hardwicki). As well as hermit crabs: large Striped hermit crabs (Clibanarius sp.) and one small Banded hermit crab.
But these fugly well camouflaged Sea toad spider crabs (Schizophrys sp.) I found most appealing. They have living animals stuck on their bodies and legs. And thus resemble encrusted pebbles that are easily overlooked.

Snails and other molluscs were also abundant. With very many Fan shells (Family Pinnidae) everywhere. Marcus also saw a variety of conch snails (Family Strombidae). These snails and clams used to be collected aggressively but since access to Pulau Sekudu has been restricted in Mar 08, perhaps the populations have recovered?I saw several of these pretty Pink moon snails today. All busy burrowing along the sand or even among the seaweeds. I still don't know what they are.

Evelyn also spotted the rare Bailer snail (Melo melo)!

Of course, there was a frenzy of nudibranch spotting ... by the other team members.The only slugs I saw were these Bryopsis slugs (possibly Placida dendritica). The 'hairy' projections on their bodies match the slender hairy seaweeds where they are usually found. I'm sure the others will blog about their nudis very soon.

There are a few mangrove trees that have settled among the huge boulders on this tiny islet.
In line with my current mangrove mania, I took the time to find out what they are exactly. There were two large Perepat (Sonneratia alba) with their feet below the high water mark.Higher up among the big boulders were a very large and well grown Mangrove cannon-ball tree (Xylocarpus grantum), two Api api bulu (Avicennia rumphiana), and one tree that seems to be Buta buta (Excoecaria algallocha).In addition, there were shrubs of Sea hibiscus (Hibiscus tiliceaus) and of Peria laut (Colubrina asiatica). Well, Pulau Sekudu's attraction is really its marine life. But still good to know it shelters some mangrove trees and plants as well.As the sun peeked out at the horizon, the tide came in and it was time for us to go home. We didn't even have time to check out the reef edge of the lagoon at the islet as the tide wasn't very low.

From our very short trip, it seems Pulau Sekudu is doing well. We should visit this islet more regularly to better document the diversity there and keep track of any changes that may impact it.

More about the fishes I saw today at Pulau Sekudu.

Other blog posts and uploads about this trip

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