Where are the sand stars?

Was back to Changi this morning with Ron and Yikang. We thought we could do a quick survey of the sand stars (Astropecten sp.) and the button shells (Umbonium vestiarium) for my project. However this morning, we couldn't really find any sand star at the beginning. This is perplexing!

After a thorough hunt by the three of us, only about four or five quite small sized sand stars were found. I'm glad at least there are some. Usually the whole shore is covered with numerous sand stars so we don't know why there was so little of them found. Many questions were raised on my mind.


Nevertheless there were a few other interesting creatures found like this ghost crab.


Several geographical sea hares were also found along the sand and seagrass areas.


Though peacock anemones are not true anemones, their beauty definitely cheers me up.


The find of the day must be this tiny green sea star that I spotted while looking for sand stars. Though not visible in this photo, the central area has knobs forming a ring. It is highly suspected that this is a juvenile knobbly sea star like those found at Changi by the other shore friends before. Glad I could see it for myself.


The underside or the oral view shows the tube feet with suckers.


This part of Changi was still relatively quiet this morning and while the sun was beginning to rise, the trio decided to quickly get a cab to check out another part of Changi where many sand stars were found just two weeks ago.


The entrance to this second stretch is quite rocky and immediately while entering, we found this group of thunder crabs aggregating. Looks like a drama.


I have no idea what have they done or why they are gathering like that? Hehe.


Ron quickly found a stunning orange-red rock star (Asterina coronata). It looks like it is carrying the rock... erh that takes some imagination to picture that.


Putting it into a pool of water made this stunning star relaxed.


We found a total of five rock stars in quick time. Wow! This is another one.


One more, clinging on to the rock.


Peacock anemones are also found at this part of Changi, they are really beautiful.


This is a swimming anemone (Boloceroides mcmurichii) that is quite small in size.


This one is bigger, with longer tentacles as well.


Carpet anemones are no exception. Many were spotted on the two stretches of shore visited today.


This is the ONLY sand star found on the second stretch of Changi shore. The previous batch of five sand stars were not photograph as we were rushing.


The sun rises, the tide returns and off we went for breakfast.

So where are the sand stars?

Were they burrowing deeper? Were they deeper downshore? Were they predated on? Were their prey missing? Did the poachers collect most of them away?

We also hypothesized it might have something to do with the moon. Given the two weeks ago (new moon), plenty of sand stars were found while one month ago (full mooon) only one pathetic sandstar was found on the same place.

However, after a quick check at last year's sand star sighting in Chek Jawa and Changi, the moon does not really affect their activity and spotting by us. Seems weird.

Could it be because of their prey are missing or have moved down to deeper waters? The sand stars mostly eat button shells (Umbonium vestiarium) which we did not find today as well.

According to Berry and Zamri (1983), it was stated that "progression of this cohort (of button shells) indicated that young settling in May-June grew to full size (11-13mm diameter) by January-March the following year and that virtually all died during their second year, presumably having spawned in March-May". This paper also stated "the older cohort were always more abundant upshore than downshore except in May 1982".

Could the absence of button shells in May cause the lowering number of sand stars? Will heavy recruitment of button shells in June/July means the return of sand stars?

There are so many questions unanswered, hopefully we will know why soon.

Reference:
Berry, A.J. and Zamri bin Othman (1983). An annual cycle of recruitment, growth and production in a Malaysian population of the trochacean gastropod Umbonium vestiarium (L.). Estuarine, Coastal and Shelf Science 17: 357–363.

Changi rocks

At 0430, a small group of four checked out Changi early this morning. I have not visited this part of Changi before and it's a bit more rocky. Though seemingly there is no life from far, you will be surprised to find lots of life teeming underneath the rocks or at the crevices.


Other than the bigger blacker anemone on the right, can you make out the numerous invisible looking smaller ones?


Chay Hoon very quickly found this flatworm. The blue edge is actually not continuous. Look closer and you will find that it is made of of many blue dots lining at the edge of this beautiful flatworm.


Just beside the flatworm, I found this pretty nudibranch (Chromodoris tumulifera) which I encountered before at East Coast.


Soon, Ria, Chay Hoon and I each found one of this really stunning Hypselodoris nudibranch. I have never seen it before.


This one looks not so dark compared to the above one.


And Chay Hoon found the third one possibly eating at the blue-green coloured sponge.


Underneath rocks are teemed with life. Other than tunicates and sponges, you can also find tiny and cute porcelain crabs.


This crab is very interesting. A bit similar to velcro crab with bits of stuff like sponge on its body. But we don't know what exactly it is.


This hoof-shield limpet (Scutus sp.) was also found underneath rocks. Heard from Ria that is not common. It usually envelops its flat shell in its huge body and is often mistaken as slugs. My first time seeing this guy. :-)


This cowrie looks like the guy in the previous photo and also was initially found underneath rocks.


Yet again, under another rock, Ria found this lovely pair of snapping shrimp. The mama is carrying eggs, can you see? Wow.


It's a shame to say I've never see a rock star (Asterina coronata) before. They are usually found on or underneath rocks.

According to Dr Lane's "A Guide to Sea Stars and Other Echinoderms of Singapore", its small size (radius about 2cm) and dull, mottled colouration make it easily overlooked and could be more common than supposed.


Looking at the underside, this is the oral view of the rock star.


More than four of such rock stars were found on the rocks today. That's very exciting.

Basically underneath rocks are great places for creatures to hide is because that they will not be exposed to sunlight or air and can be kept moist at the same time.


Hydroids are also growing quite well at this shore, thus emphasizing the importance of wearing long pants or else the stings will ensure your leg to look like a horrible one. Haha.


I'm amazed to see so many live blood cockles on the substrate. But to think twice, don't think it's really safe to eat. :P


There are also several green and whitish corallites attached onto rocks. Wonder what species of coral is this.


Though no soft corals were found this time, there are still hard corals encrusted onto the rocks of the shore.


Ivan shared with us his find of this interesting sea cucumber which till now we don't know what is it.


It's interesting to see that octopus from the northern shores tend to be greyish pink, perhaps because at most of the time, there's not much rubble for it to change colour to.


Sponges come in different colours and this one in stunning red indeed attracted my attention. Pay attention to its surrounding and you might spot a greyish fishy looking creature.


This fish is long and looks eel-ish. Haha. Any idea what is this?


It's heartening to find different lifeforms on the shore. Within a snapshot frame of this photo, many animals are represented. And we didn't position them like that. There are ascidians, sea cucumber, a rock star and also a Hypselodoris nudibranch. Wow, that also adds the nudibranch count of Hypselodoris species to four.


Towards the end of the exploration, we found plenty of bristle worms. They are also known as fire worms. Why fire? You will know it since you are warned not to touch it.


One may wonder, what on earth feeds on these nasty worms? I'm glad the answer was revealed instantly when we spotted a swimming crab feasting on one. Soon, another crab approached to join the feasting.


A predawn (yet sleepy :P) trip usually ends with a stunning sunrise! What a great way to start a wonderful day in the morning.

Changi indeed rocks and is fascinating. Will be back tomorrow to check out the softer part of Changi. Too bad no astropecten sand stars were found today. Was there today mainly to document and recce for the sand stars.

That means more work to measure and document them tomorrow. Hahaha.

Sleepy humans, lively Sisters

Another low tide arrives and at a very early morning of Vesak Day, the gang set off from Marina South Pier at 3.15am for Big Sisters Island. That means we all got actually very minimal or for some, even no sleep.


Today's tide wasn't very low but good enough to see lots of fishes swimming in the lagoon. As usual I am horrible in fish ids. It will be great if there's help to get them identified.


This is the clearest shot of a fish about 8cm in length.


There was a very nice reef fish which was spotted before at Little Sisters, I took out my camera, and when I snapped, it already was swimming away. Sigh, this is the only shot I have.


Moving over from fishy business, we have the sticky business. This black sea cucumber ejects white threads when disturbed. And Jerald was asking at the end of the trip what happened to his track pants with lots of white sticky thread. We bet he has stepped on one unknowingly. Ouch.


Evelyn and Vyna were marvelling at the crabs making out aka mating. The male is huge as you can see.


Another crab here which is not as commonly seen, the mosaic crab. It is not edible okay, if you want to ask can eat or not. But you can eat anything if you want, at least once.


There were a lot of flatworms! This tiny one was spotted by Vyna.


Yet another one by Vyna!


This bigger black with orange dots flatworms was discovered by Yuchen.


And finally I found a totally black coloured flatworm with orange fringing at the sides.


We also encountered the leaf slug which I didn't bother to take a photograph given the not so low tide and murky waters when we stepped around. But I managed to take a photo of this Glossodoris atromarginata nudibranch.


I was looking at a toadfish with Evelyn (no photos, too murky) and then Jerald and Vyna called me as they found an octopus. And when the octopus was moving it, it looks impressive.


This is the SAME octopus, but totally different coloured compared to previous photo. They are indeed master of camouflage.


Liana pointed out to a snail that has a pink shell and beside it is a baby anemone that is very small. Very cute.


This snail is interesting as it is bright orange in colour and I've not seen it before.


Turning it over, we found that it is alive!


There was another snail found by Chay Hoon and this one is really pretty. I'm sure Ria will blog more about it soon.


Beside the pile of acorn worm pool, Chay Hoon and I found this slimy long thing. Could this be the acorn worm itself? I wonder.


Anemones are cute, including this tiny one. We also saw the Gigantea and Haddon's carpet anemones.


I believe the FIND of the day is this giant clam (Tridacna squamosa) growing on top of faviid coral. This species can be distinguished by the presence of large leaf-like fluted edges on its shell called 'scutes'.


A closer look reveals the mantle tissues which acts as a habitat for the symbiotic single-celled dinoflagellate algae (zooxanthellae) providing a major portion of its nutrition. During the day, the clam spreads out its mantle tissue so that the algae receive the sunlight they need to photosynthesize.


Moving the attention more to homosapiens, here's Evelyn's sketch on the sand, Big Sister aka Da Jie Dao in chinese.


Most of us were quite sleepy especially towards the end... Haha, especially Liana :X


Yuchen got cut by an unknown object and immediately, he received medical attention from many of us. That's how efficient and helpful we can be.


I believe he has lost a bit of blood. Arrgh.


As the tide returns, a morning glow shines behind St Johns Island.


And its a very beautiful sunrise!


Stunning sunrise over St John Island.


More sunrise, this time taken together with Singapore Straits.


And the sleepy humans continue to catch up with their sleep while the lively Sisters shore continue to thrive and embrace the start of a new day.