Archive for the ‘Public Walks’ Category

So we headed off from NUS this time, carrying containers and all sorts of stuff to be used in activities with the MGS girls at Changi Beach. Arriving earlier than expected, we settled down at a small sheltered ‘hut’, and we noticed..


Ladybug! Henrietta, Kok Sheng and I got all excited wanting to snap shots of this tiny cute ladybug that was on the floor behind us. KS then put it on a leaf, attempting to take a more natural-looking shot :D


Slightly more ominously though, was a dead Mynah about two metres away from us. Poor thing already had ants all over it. Robert arrived shortly, bringing with him a moult from a Flower Crab, and two Sea Urchin tests.

Sea Urchins leave behind a calcerous test that is akin to a skeleton that an animal leaves behind as the soft tissue decomposes.

mgsThen the MGS girls arrived for their two hour workshop. Here’s a picture of Robert with his group – the Knobbly Seastars! A quick safety brief and off we went to the intertidal area!

A short introduction to tides led to a discussion on how intertidal creatures live in an environment where ranging temperatures, salinity and moisture all pose a challenge for survival.

The New Moon and the Full Moon are all times to take note of – thats when the tides are the lowest or highest in a month. Here’s more on Spring and Neap tides.

sea-cucumber-unknownSea Cucumber, unknown. This little critter was completely buried in the sand, and even without close inspection you can see the many thorn-like structures on its skin! Colour is drab brown to blend in with the sand where it usually lives.

sea-cucumber-thornyThorny Sea Cucumber (Colochirus quadrangularis) [Thanks Ron for the ID!] again, this time with its filter-feeding apparatus out for all to see. Looks like fireworks to me. Sea cucumbers are part of a group called Echinoderms, and these include the very popular seastars, sea urchins that people fear (coz of the spines), and sand dollars that most don’t know about.

Echinoderm means ‘spiny-skin’ in Greek, and this prickly nature is what most echinoderms have. Hard spines are clearly visible in sea urchins, smaller, less distinguished ones are present in sand dollars and seastars, and  most sea cucumbers lack hard calcerous spines.


The Striped Hermit Crab (Clibanarius infraspinatus) here is beautifully striped, and quite big too. This one got quite irritated with Robert and gave him a strong nip on the palm. As a hermit crab grows bigger, it also outgrows its shell – because of this, it needs to keep changing shells to accomodate its size. Refrain from picking shells at the beach because you could just be depriving a hermit crab of a home!


I nearly stepped on this Hairy Sea Hare (Bursatella leachii) – but thanks to Hen’s and KS’ shouting I froze in time. Some sea hares have internal shells, most have a pear-like body shape, and they seem to also be seasonal – sometimes you see many of them and sometimes even spotting one is difficult. This sea hare feeds on cyanobacteria and swallows large amounts of sand in the process, much like an earthworm!


Dragonet, (likely Callionymus schaapii). Don’t know anything about this fish, and finding on the web isn’t very conclusive. Anyone know anything about this one? There was some debate on whether it was a flathead or not. Thoughts? [Edit]

According to Ron, that’s likely the species name for this fish, and flatheads generally have a longer head, and dragonets have a shorter one.


Cake Sand Dollar. In the background photograph you can see tracks laid by a Sand Dollar, that is moving constantly through a thin layer of sand, feeding on organic debris as it does so. They are pretty common on our beaches, and quite brittle/fragile too! Do take note of where you step on when you are at the beach.


Spider Crab. Notice the pointed ends of the Spider Crab‘s legs, and how well camouflaged it is with its odd shape, and drab colouring (mostly sediment on its body here). An elusive creature, the Spider Crab is often difficult to spot as it minimises movement to avoid detection by other creatures.


Razor Clams, also known as Bamboo Clams, are able to ‘swim’ and bury into the sand if they’re needed to very fast, despite its elongated appearance that intuitively seems like its hard to burrow or swim efficiently. Siphons at the end of the soft body (the striped part you see here) jet water out, and are also part of an inward/outward flow of water from which they filter feed from.


Mantis Shrimps are not shrimps! They are even less closely related to shrimps than crabs are. Usually growing up to a length of barely 10cm, the largest specimens found could easily reach 30cm! Mantis shrimps got their common names from their strong and powerful front pincers – and so are largely grouped as Spearer or Smasher Mantis Shrimps. Some Smasher mantis shrimps have even been known to be able to smash their way through aquarium tanks that have not been reinforced!


Helmet Snail, (Semicassis bisulcatum). This pretty Gastropod was moving around when Henrietta spotted it – causing quite a frenzy where Ron and KS were jostling around to get a good picture of this unidentified species. As you can see from the border photographs, thats a sequence snapshot of the movement of the snail. (:


The MGS girls were exclaiming when this horseshoe crab was brought into the scene by Robert, who found it nearby. Already dead, there was a slight decomposing smell if you went too close.

This Coastal Horseshoe Crab (Tachypleus gigas) can be identified from its relatives through its triangular shaped tail (in cross section). The other HSC, the Mangrove HSC, has a conical shaped tail. The name HSC is actually a misnomer, as these ‘crabs’ are actually more closely related to spiders than crabs!

HSCs are very fragile creatures – and Robert was demonstrating the way HSCs flip themselves back up if they become overturned. Biotechnologies have recently discovered that the blood of a HSC can detect gram-negative bacteria (e.g. Samonella spp., E. coli, STD-causing bacteria), and because of this HSC numbers have dwindled as pharmaceutical companies who practice unsustainable harvesting of these creatures suck them dry of blood (pun unintended).


Certainly my first time seeing an outdoor workshop with secondary school students – it’s very heartening to see that our younger generations are still open to this kind of education: hands-on and traditional biology, the one that always captures people’s attention, and hearts.

Also keeps reminding me that knowledge really, shows us the extent of our own ignorance. Great trip!


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[Edit]: Thanks to Ron, there’s more information on the hard coral, squid and the Fiddler Crab’s name is complete now :D

An impromptu invitation by Luan Keng to join the public walk on Sunday led to a great walk with lots of pictures and marine animals seen (: Here it goes!


This tour of the landfill facility on Pulau Semakau saw us sitting for a slideshow presentation and a van ride of the island, passing by the marine transfer centre, the generator building, dumpster trucks that transport waste to the tipping cells that contain the ash, and the southern most tip of the island.


Shortly after the tour,  my group (Pufferfish!) was lead by June into the intertidal area, where we stopped by the Sea Lime tree for a taste of some of the riper fruits, and the group had their first encounter of mangrove trees (Rhizophora apiculata).


Right under a bunch of mangrove trees were Fiddler Crabs (Uca annulipes). Male crabs have one large claw (cheliped) that they use in aggressive territorial and courtship behaviour, by waving it up and down intermittently. The burrow seen beside the crab is actually its home.


Sponges (Phylum Porifera) are fairly common in the intertidal area, and they also come in many colours, bright and dull. And if they seem like plants to you, they are actually simple animals! Made up of a few types of cells, they do not have mouths or a digestive system! So how do they eat?

A sponge actually filters water for food, and as the canals in their branching structure narrow, microscopic organic particles, bacteria and plankton get taken up by these cells. Don’t get fooled and touch one though, some sponges can cause irritation – they’re not to be bullied!


We soon came upon the Tape Seagrass (Enhalus acoroides) that is the longest seagrass that can be found in Singapore’s shores – with leaf blades measuring up to 1.5 metres in length! A female flower and male pollen are shown here – male pollen float and raft along, looking like bits of styrofoam, and soon enough catch onto the flowers of the female. Fruits will form soon after.


Sea Cucumbers! (Class Holothuroidea) We saw a few types today, but only managed to get one on film – the Eye-spotted Sea Cucumber (Stichopus ocellatus).

Almost all sea cucumbers are detrital and/or filter feeders, which means they either feed on microscopic organic material, or plankton. Certain species, once degutted, dried and cleaned, are considered delicacies.


This Snapping shrimp has (unidentified) one enlarged pincer that it uses to create a loud bang (see here for more) that stuns or kills its prey. The actual mechanism involves a jet of water that shoots out from a socket within the pincer, generating a bubble that collapses with a bang as it stabilises, the entire process lasting all of 300 microseconds. The biggest one I’ve seen so far, this one was nearly 10cm long.


The Common Sand Star (Archaster typicus) is, as its name suggests, very common. This is less so today than in the past however, as land reclamation in Singapore has resulted in the loss of the original coastline. Often buried in the sand, a five-armed impression can usually be seen above where they are buried.

Though most seastars are found to be five-armed, it is not unusual to find a four or six-armed seastar as well. Seastars use a water vascular system instead of a blood circulatory system like ours, and hence will dry out and die if they are left out in the sun for too long.

As you can see from the index finger comparison, this is the size of a mature common sand star. Tube feet on the underside of seastars allow them to walk via the water-vascular system as well – and in addition, the common sea star also has spines that allow it to burrow quicker.


Noble Volutes (Cymbiola nobilis) have a beautifully zig-zag patterned shell and black and orange marked body, and this one we saw here is laying eggs. The eggs are translucent, and as can be seen, as big as the noble volute itself. Tiny baby snails will emerge from each egg capsule.

Due to over-collection by people as decorative shell items or even food, this animal is currently listed as ‘Vulnerable‘ in the Red List of Threatened Animals in Singapore.


Seen here from top and bottom views, is the charismatic Heart Cockle (Corculum cardissa), and is part of the family of true cockles. Contrary to popular belief, the Blood Cockle, or ‘See-Hum’ as many locals know it, is not a true cockle, but an Ark Shell (Arcidae).

The shell of this cockle is very thin and flattened out, evolving in such a way that it allows light to penetrate through – giving the zooxanthellae found inside enough sunlight to photosynthesize and produce food for itself. This symbiotic relationship (where both parties benefit) is not a very common relationship found in bivalves.


Moving along, caught and placed into plastic containers for easy viewing were some flatworms! Flatworms (Order Polycladida) are unsegmented worms and can be brilliantly coloured, sometimes seen crawling along the seabed or swimming beautifully with the edges of the flatworm fanning out like a spanish dancer’s dress.

In the top left photograph we have the Red-striped flatworm (Maritigrella virgulata) and the other is the Spotted Black flatworm (Acanthozoon spp.). Flatworms are actually very fragile, and easily tear, and if you look closely, you can see that the edge of the Spotted Black flatworm in this photo is torn off, where the white margin along the periphery of the worm is discontinued.


The Polka-dotted nudibranch (Jorunna funebris) ranges from about 1 – 6cm long, and feeds on sponges (see top) – making it a carnivore! Nudibranches are also incredibly diverse in pattern and colour, and belong to the phylum Mollusca, the same one snails, octopuses and clams are found in!

The name noo-dee-brank means ‘naked gills’, and the gills of this nudibranch have been pointed out here. The rhinophores seen in the picture are used as chemical detectors as they move along in the water – and you can see from the six photos by the side as it moves along.


The Knobbly Seastar (Protoreaster nodosus) is massive for a seastar, and like the Common Seastar featured earlier, uses a water vascular system. This seastar however, is extremely robust due to its heavily calcified body, and this deters predatory fish from eating it.

A popular icon used by Semakau guides, this pretty seastar was also intensely targetted by the marine curio trade for sale and use as a decorative item. Young juvenile knobblies are seldom found, and it is not certain if this is because they mature or reproduce slowly.


And its time or corals! In order of left to right, top then bottom, we have: Dead man’s fingers coral (Soft coral), Sunflower mushroom coral (Heliofungia actiniformis), Omelette coral, Hard coral (Goniopora spp.), Mushroom coral, Zebra coral (Oulastrea crispata).

Soft coral examples are the Dead man’s fingers and Omelette coral, and hard coral examples are the Zebra coral and Mushroom coral.


Corals are usually colonies of animals staying together, and are often explained as a HDB flat housing many animals called polyps, and each polyp creates its own little ‘house’ called a corallite, made of calcium carbonate, beside the other polyps. Above water, they retract back into their corallites for protection and to keep from drying out, but underwater, they come out to feed.

The polyps feed on plankton and microscopic organic material – but some polyps also contain zooxanthellae, single-celled green algae that photosynthesize and share this food with the polyp, that provides it shelter in return.


Free-living corals (not stuck or anchored onto the substrate [rock surface or seabed]) examples are the sunflower mushroom coral and the mushroom coral. This coral is also a solitary polyp, and not a colony of polyps (like the Zebra coral is).

The polyps of this species are considered the largest of all hard corals, and can be mistaken for a sea anemone.

Do take note: It is not recommended that you touch any marine life or corals, as some of them might have stinging cells or may spray out liquid that can irritate the skin. Corals also have a calcerous skeleton that may have spikes or spicules that can be embedded in your skin, causing inflammation or irritation.


The Fluted Giant Clam (Tridacnidae squamosa), is listed as ‘Endangered‘ on the Red List due to extensive over-collection and a rare sight. The wavy flutes, or scutes, that clam creates are used as a ‘platform’ for the clam to extend its fleshy body to face sunlight so the zooxanthellae it harbours can photosynthesize for food.

The Heart Cockle and the Giant Clam are one of the few bivalves that harbour zooxanthellae and receive food from it in this way.


This Tiger tail seahorse (Hippocampus comes) is listed in CITES II, which means its international trade is monitored. Unlike its appearance, the seahorse is a fish, and has bones on the outside as well as the inside. The outside skeleton is inflexible, and acts like armour.

Using fins on its cheek (pectoral) and back (dorsal), it maneuvers around and uses its tail to anchor itself. It does not have a tail or pelvic fin, unlike fishes – thus, they are slow moving creatures, and vulnerable to collectors. Seahorses around the world are endangered.


Spider conches (Lambis lambis) are large snails, and have fantastic camouflage despite their relatively large size and weight. These snails are listed as ‘Vulnerable‘ on the Red List, as local populations dwindle due to over-collection and careless trampling by visitors to the shores.

Conches use their muscular, narrow foot to right themselves if the tides overturn them, and can actually move quite fast. It is also suspected they have eyes that can produce an image (unlike other snails that just differentiate between light and dark)!


Common Hairy Crab (Pilumnus vespertilio) seen here has prickly pointed legs that are used to clutch tightly to rock or coral rubble, and can hurt if picked up like this. This is a male crab, as visible by the pointed (triangular) underside.

A distressed Squid (Sepioteuthis spp.) here has squirted black ink and the black ink cloud is floating beside it.

Sea Hare has cute wings on its back, and have rhinophores like nudibranches. They are, however, very different from them. Sea hares squirt out purple ink if stressed.

The Marine Spider (Desis martensi) is about 1cm in body length, and hides in air pockets among crevices of rocks during high tide, and uses its hairy legs to ‘walk’ on water and hunt for prey.


1. Heart Urchin
2. Fan Shell
3. White Collared Kingfisher
4. Upside-down Jellyfish

I could do the mixed photographs either way like this one (numbered) or the previous one (un-numbered). Do feedback on which is better!


June was guiding this group of 11 adults – some other groups had children that looked as young as 7 years old. At the end of the walk, feedback forms were given out and the participants, happy and tired after a long day, started to fall asleep on the ferry back to mainland Singapore.

A good day today! Bright, sunny, and lots of finds today (: My first OJT trip too, excited to start learning even more about these intertidal animals as I can. (:

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