Pasir Ris: some mysterious finds

3am and Chay Hoon and I decide to check out the rest of the large Pasir Ris shore. There's larger patches of seagrasses there!The shores are rather soft, but teeming with life. In the rather clear waters of this last of the morning super low tides, there are swimming crabs, sea stars and hermit crabs.Lots of hermit crabs! In huddles here and there. Hmm, I wonder what they're up to?

And a super abundance of sand stars (Astropecten sp.).
In various sizes from tiny to large.For some reason, I saw a lot of them upside down today. I also saw the remains of a disintegrated star. Was it attacked? Or is something else happening to them? There were also many with lost arms, like this poor star with three regenerating arms.

The masses of black short-spined sea urchins (Temnopleurus sp.) was seen again.These sea urchins 'carry' stuff like shells, which is why there are so many clam shells among the sea urchins. I'm not sure why they gather in groups like this. They seem rather smaller than usual for it to be for mating. Possibly for protection?

A mystery echinoderm was this purplish sea cucumber in the middle of the sand flat.I have no idea what it is.

And a mystery fish!It has a very long first dorsal fin and pretty colours on the tail and the rest of the dorsal fin. I tried to take a closer look at it but the fish disappeared into a burrow as soon as I approached.

There were also several of these large beautiful shells on the shore.The shells are empty. I have no idea what kind of snail made this shell and where they live. In deeper water? Burrowing in the sand?

Another puzzle were these clumps of bubbles on the sand. Several were seen, like delicate glass ornaments.

Another glassy marvel is this beautiful sea anemone which I call the glass anemone because it reminds me of blown glass.It's also sometimes seen on our other northern shores. It is one of our common sea anemones that have yet to be identified.

This soft shore is full of all kinds of different anemones. Including this odd little dark anemone that I've not seen before.
A closer look reveals rows of bumps along the body column.And pretty yellow spots in the centre on the oral disk, as well as along the short arms.

These soft shores remind us very much of Changi. As in Changi, there were also some peacock anemones with attendant black phoronid worms, several small and large carpet anemones some with tiny shrimps in them. The sea pens are not abundant here, I saw only one stick-like Virgularia sp. Also missing were brittlestars, biscuit sea stars, thorny sea cucumbers and mantis shrimps that we regularly see on Changi. Although there were lots of sand collars, I didn't manage to find any living moon snails.

There were not many moon crabs (Family Matutidae) at Pasir Ris. I saw this rather 'weedy' moon crab. It was still alive, although it wasn't very lively.Its body was not only overgrown with seaweeds, but also had other little animals living on it. I'm not sure what's happening. Is the poor crab sick? Paratised by some nasty parasitic barnacle? On Changi, we usually see this situation more on the swimming crabs and not the moon crabs.

There were several Sentinel crabs (Macrophthalmus sp.) on the shores.In the same larger group as fiddler crabs, these crabs also have eyes on long stalks. But their pincers are equal sized.

Further up on the higher shore, there was this other crab in a burrow, also with long eyestalks.Is it also a Sentinel crab or some other crab? I have no idea.

And what a lovely surprise to come across a seahorse (Hippocampus kuda)!A very pregnant papa seahorse he was!

Chay Hoon found SIX of these little black yellow-spotted Gymnodoris nudibranchs!
These little nudibranchs require a keen eye to spot as they are tiny and well camouflaged.

She also found several of these odd looking flatworms.There were lots of them out and about this morning. Even blind me saw some of them. The odd thing about them is the pair of 'tentacles' sticking out of the body. I have no idea what kind of flatworm this is.

We had a pair of these flatworms in the box to take closer photos of them ...Suddenly the little one attached itself to the big one and a tangle of twisting ensued. Oops. Possibly there is something going on to do with baby flatworms?

Flatworms are hermaphrodites. Each flatworm has both male and female reproductive organs. So when two flatworms meet they can exchange sperm. Shortly after twisting about for a while, the two flatworms calmly separated and moved off in separate directions.

Wow, what a fantastic morning out on the shore. More questions than answers, but that goes to show how much more there is to learn and discover about our shores!

As we were exploring, a friendly passerby with a plastic bag approached us. We showed him some of the fascinating marine life there. We asked about the contents of his bag and he showed us a dead fish, several hermit crabs and sea stars. He intended to try to use them as bait, 'for fun' in his fishing later on at high tide. We persuaded him to return all the other marine life and just use the dead fish. He was very friendly and agreed to do so.

Pasir Ris Bliss: Stars!

3am and I'm on Pasir Ris alone. It's my first time on this shore but have heard from Kok Sheng that there's lots of sand stars there. My job this morning is to take photos of them and their measurements. And wow! There sure were lots of sand stars!They came in all kinds of colours, in various sizes,And all kinds of patterns too.Sand stars belong to the genus Astropecten. We're not sure if the one with the pretty patterns on the arms are a different species from the plain ones. It takes close study by scientists to sort out issues of species. So I'm glad Kok Sheng is on top of this question.

The sand star has large flat spines along the sides of the arms. There are also large squarish plates on the sides of the arms.The upperside of the body is covered in tiny patches of bristle-like structures. The white spot is the madreporite; water is sucked into the sea star through this seive-like structure. The mouth is on the underside with grooves along the arms, through which emerge pointed tube feet.

Some of the sand stars had little white snails on them.Even tiny sand stars like this one. Which is why the snails looked relatively large. I believe these are parasitic snails. I'm sure Kok Sheng can tell us more later on. I've seen these snails on the sand stars at Changi as well.

While most sand stars have five arms, there are some with four arms. Elsewhere, I've seen them with six arms too. Here is a four-armed sea star in the little measuring tray that I used to take quick photos of them before returning them.Alas, today, I saw many sand stars with broken off arms. Otherwise, though, they seemed healthy. They did not have 'rotted' wounds or lesions or other signs of disease.

Sea stars can purposely drop off an arm if they feel threatened. This is how they might escape a predator that has chomped on an arm. Or if a stone happens to roll onto an arm.

For this reason, those of us studying stars should NEVER pick up a sea star by the arm. Even big ones like the Knobblies. We should gently lift them by the central disk.After taking their measurements, we should quickly put them back where we found them.

Unless there is a good reason for doing so, it is best not to touch sea stars, especially not to remove them from the water. Taking photos with them out of the water is not a good way to promote care for our shores. Those of us who love our shores should avoid doing this and avoid encouraging people from doing this.

I took measurement of nearly 40 sand stars! I stopped after heeding the protestations of my aged knees and back. So sorry Kok Sheng.

There were also other stars on the shore (which was sprinkled with large rocks), including several Crown sea stars (Asterina coronata).
And I came across one medium sized Cake sea star (Anthenea aspera). How nice to see this star on a rather silty shore.There were also other echinoderms. A few buried ball sea cucumbers (Phyllophorus sp.), and black sea urchins (Temnopleurus sp.). LOTS of black sea urchins!This gathering of very many sea urchins stretched all the way out into the deeper waters!We've seen this sort of gathering of black sea urchins on Changi as well. But it has been a long while since I've come across such a gathering.

The black sea urchin has short black spines. And tends to 'carry' things such as bits of shells, dead leaves, seaweeds and other debris.
Like other sea urchins, the mouth is on the underside. The black sea urchin often has a long banded worm-like thing curled around its mouth. I've seen this several times also on the black sea urchins on Changi.
Quite creepy actually! I have no idea what the worm-like thing is or what its relationship is with the host sea urchin. Yet another mystery that needs more study!

Pasir Ris Bliss: more critters!

Besides stars and urchins, the Pasir Ris shore was also alive with all kinds of other animals!Under the scattered stones and rocks there were octopuses! I saw two of them, but just their arms sticking out from under a large rock. They seemed quite large and appeared to be the kind that we see on Changi, rather plain and smooth, unlike the more colourful ones we see on our Southern shores. The tide was very low so they weren't out hunting.

What was out hunting though, was this Tiger moon snail (Natica tigrina).Moon snails love to eat button snails. I looked and I looked (because Kok Sheng is interested in them) but didn't see any button snails, not even on the small sand bars nearer the low water mark.

The shores were lively with Flower crabs (Portunus pelagicus) of all sizes, and I saw this large Moon crab. The old scientific name of this crab is Matuta lunaris and now more and more people refer to it as Ashtoret lunaris. Here's some details from the stunning Systema Brachyurorum Part 1 by Peter Ng et. al (2008) in The Raffles Bulletin of Zoology, "an increasing number of workers have chosen to recognise ... Matutidae and Calappidae as two taxa as distinct families ... Until more work is done, we take the somewhat more conservative approach and keep the Matutidae and Calappidae in one superfamily, Calappoidea."

Quietly having little parties in small groups of two or three were lots of tiny little hermit crabs.These are probably the Tidal hermit crab (Diogenes sp.). There were not that many Striped hermit crabs (Clibanarius sp.) unlike at Changi.

Another cuddly couple was this goby and snapping shrimp!Some gobies live together with a snapping shrimp in its burrow. The more keen-eyed goby keeps a look out for danger and annoyances (such as shore explorers). Meanwhile the short-sighted snapping shrimp does the house-keeping on the burrow like a little bulldozer. It was dark and I guess they don't equate a weak torchlight with danger. But after this flash photo, they both disappeared into the burrow in a flurry of sediments.

The pools were thick with tiny little gobies. There were the usual Brown shore gobies (Drombus triangularis) and Shadow gobies (Acentrogobious nebulosus). But here is a pretty goby with little red spots whose name I don't know. Lacking a name doesn't stop us from admiring it.

Worms might seem icky to many, but I find marine worms quite fascinating.These fluffy worms with a double fan in trendy pink and black belong to the Phylum Phoronida. The phylum has less than 20 species! That's a really small phylum. Consider that fishes, birds, gorillas, us all belong to one Phylum Chordata. These Phoronid worms are often found with Peacock anemones (Order Ceriantharia) and indeed, this bunch was found near the bottom of a Peacock anemone that had retracted into its tube.

While bending over to take photos of sand stars, I noticed this colourful tube worm making a quick foray outside its tube.Isn't it pretty?! With iridescent body and feathery gills. OK, we got to ignore the scary tentacles on the head.

And here's a bunch of stuff sticking out of the sediments. I see this all the time and still haven't got a clue what they are.Probably the tentacles of some sort of worm. I also saw a short and small ribbon worm (Phylum Nemertea) with stripes, and of course, lots of bristleworms.

But the shore was truly teeming with tiny little sea anemones of all kinds.Thanks to having to keep bending down to measure the sand stars, I got a good look at them, even these very tiny ones!And there were two of these beautiful large sea anemones that I've not seen before. They had a inner ring of intriguing lobed structures.
I've seen something similar, but these were transparent with white markings and seen near mangroves at Kranji and at Sungei Buloh. We must bring Dr Daphne to Pasir Ris when she's next in town!

The short stretch of Pasir Ris that I went to today was mostly soft and silty with scattered rocks and stones. There wasn't much on the stones aside from a sprinkling of sponges and some seaweeds. Although there were a few tiny patches of hard corals!
This is Zebra coral (Oulastrea crispata) that is often seen on our Northern shores, but in tiny colonies.

There were also few small patches of Spoon seagrass (Halophila ovalis) with big green leaves, like the kind we see at Changi.There's much more of the shores to explore on Pasir Ris, and we must certainly find some opportunities to do so.