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.
Then 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, 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.
Thorny 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!