Back to Cyrene Reef

Yesterday, I was back to Cyrene Reef with a few other RMBR volunteers. It's been a while since I last visited this little reef, and thus I was really quite excited about the trip :)


Cyrene Reef is a patch reef that is only exposed during very low tide. We set off when it was still dark, so that we could reach the exposed reef at first light.


And here's our boat! Took this photo when I was sitting in the rubber dinghy on my way to the exposed reef.


One of the nicest thing about Cyrene is the numerous Knobbly Sea Stars (Protorester nodosus). Interestingly, I could still remember during my first trip here, the whole gang of us walked all around the reef and we only managed to find 1 of them. But during my second trip a few months later, somehow their population went into an explosion, and we started seeing them every where!


This Knobbly Sea Star unfortunately only had four arms left.


I found this Knobbly Sea Star on the soft coral, and had initially thought that perhaps it was just sliding over it. But when I picked it up and looked at its underside, I noticed that its stomach was out and there were still little bits of particles stuck to it. Was the sea star feeding on the soft coral?


Found this knobbly which somehow looked like an albino - the usual knobblies normally have darker nodules, but this one is the same colour all over.


After a while, SY found the Pentaceraster mammilatus - a sea star which I hadn't had a good photo yet.


SY also found this other sea star which looked a bit weird. It has much smaller nodules and thinner arms.


On the upperside, it has web-like patterns which resembles those of the Pentaceraster mammilatus.


At the tip of its arms on the underside, there were little spines that was not typical of Protoreaster nodosus.

Is this a new species, or is it a hybrid? If it is the latter, it can really be a little worrying, as hybrids are usually infertile, i.e. they cannot reproduce! Hybrids may compete with the original species for food and other resources, but since they can't reproduce, they may end up causing the population of the original species to be reduced as the latter were out-competed!


Seemed like SY has quite a bit of sea star luck, as he also spotted this Cushion Star (Culcita novaeguineae).


And at the sandy shore, there were lots of Sand-sifting Sea Star (Archaster typicus). The above 2 has paired up, getting ready to release their eggs and sperm into the water. Studies shown that the actual spawning may occur 2 months after the pairing.


Among the seagrass, I found a Stonefish Sea Cucumber (Actinopyga lecanora). On other islands, I mostly find them hiding among rocks or corals, and rarely among seagrass.


There were quite a number of Black Synaptid Sea Cucumbers too.


RH found this Flatworm (Acanthozoon sp.), which obviously got its common name because it's very flat! It is thus able to slide into tiny crevices to hide from predators or to seek for prey. Flatworms generally feed on small or sessile animals.


Sometimes mistaken to be flatworms, this is actually a Leaf Slug (Elysia ornata). It feeds by sucking the sap of the Bryopsis algae, and is able to retain the chloroplast and use them for photosynthesis!


AP found this little Hairy Sea Hare (Bursatella leachii). Seasonally common, we can sometimes find hundreds of them on some of our shores!


I did not have much luck with nudibranchs for this trip, and only found 2 of them. The Funeral Nudibranch (Jorunna funebris) is a cute little slug that always reminds me of Snoopy when I see them.


The Black-margined Nudibranch (Glossodoris atromarginata) was the other one I found. The term "nudibranch" means "naked gills", refering to the flower-like gills on the back of most species.


We spotted a Mosaic Crab (Lophozozymus pictor) among the seaweed. This is the most poisonous crab in Singapore, and studies shown that the poison from one crab can kill as many as 42,000 mice!


I had thought that Thunder Crabs (Myomenippe hardwickii) feed only on shells by cracking them with their huge claws, but apparently they catch fish too! In fact, the little fish it had in its left claw was still alive when I witness this scene.


There were quite a number of Cauliflower Coral (Porcillopora sp.) colonies, and I found little crabs living in many of them.


Cyrene Reef also has many mushroom corals. The above is a Mole Mushroom Coral (Polyphyllia talpina). It is a colony of many coral animals actually, and not just a single animal! The little tentacles you can see above belong to many tiny coral animals called polyps.


SY spotted this sea anemone that was somehow out in the open, instead of being attached to any hard surface or had its body column buried in the sand.


Soon, tide was rising and it was time to go. On my way back to the boat, I came across this disused quadrat lying among the seagrass. I was contemplating whether I should take it back with me to dispose it properly, but I noticed it had already became a micro-habitat with a colony of zoanthids stuck to one corner, and various algae, seagrass and sponges etc stuck to various places. I didn't want to kill those marine life, so decided to just leave it there.

On the whole, it was great to be back at Cyrene Reef!