Tuesday, June 9, 2009

Tanah Merah Sandflat

Tanah Merah before land reclamation used to a stretch of natural shore with malay villages along the coast. And among which, Mata Ikan used to be a wonderful sandy shore where scientific studies were even conducted to study zonation in a typical sandy shore and another study on intertidal gastropods in the early 1970s. A post from the Good Morning Yesterday blog shows the natural shoreline photo from the past and more details on what life used to be in the past.

Sometimes, I really want to take a time machine to visit our pristine natural shores in the past before they were impacted by reclamation, sedimentation, poaching etc etc etc. Though it is indeed impossible to do so, we can at least now help our next generation save what is left.

Though Tanah Merah sandflat is not natural (because it was reclaimed), it is also not dead at all! When I was there with some friends this morning, there was also a family out at the shore admiring the snails and other marine life.

We arrived much earlier before sunrise to catch the low tide and among the creatures sighted today will be the Sand collars of moon snails (Family Naticidae). The sand collar is actually the egg mass of the moon snails.

And this is a beautiful Ball moon snail (Polinices didyma) prowling in the sand. It has opaque white bands on its pair of tentacles.

Another pretty moon snail encounter on Tanah Merah sandflat will be the Lined moon snail (Natica lineata).

Yet again, this moon snail is prowling with its large body!

Moon snails are fierce predators. They feed on bivalves and snails. A moon snail wraps its huge body around the hapless prey to suffocate it. If this fails, it has a gland at the tip of its proboscis that secretes an acid to soften the victim's shell. With some help from its radula, a hole is created. The hole is usually neat and bevelled.

The numerous Button snails (Umbonium vestiarum) is definitely one of the main diets of moon snails at Tanah Merah.

Another predator of the button snails will be this Flower crab (Portunus pelagicus). It was interesting to see the crab handling the snail!

Another noteworthy scene witnessed about the flower crab will be this find by James where two seemingly different crabs actually belong to one crab. One is alive, the other is the moult!

Other than countless button snails, this Tanah Merah sandflat is simply just thick with Cake sand dollars (Arachnoides placenta). And once in a while, we encounter Sand stars (Astropecten sp.) which seem to be bigger at Tanah Merah as compared to other shore locations like Changi and Pasir Ris.

Andy and Collin later shared with me that they saw a large Common sea star (Archaster typicus)!

Later, there was a discovery of a white bucket with lots and lots of hermit crabs! We suspected that someone went around collecting them for fun, but eventually decided not to bring it home. Sigh. They were later all released back to the shore.

It's good for any ordinary people to visit and learn more about our shores and marine life. But sometimes, we just "love our shores to death" by doing more harm than help or appreciation.

Talking about hermit crabs, I caught this pair of Striped hermit crabs (Clibanarius sp.) orange-handed doing some hanky panky. We decided to left them alone to do whatever they want.

We do not collect dead snail shells home because hermit crabs need these shells for home!

And their shell also give an idea of the range of snails that are living in the shore, yet burrowed when alive and thus not visible unless they are occupied by hermits later.

There was this rather big snail shell occupied by a hermit crab and it seems to resemble somewhat of a Helmet and Bonnet snails (Family Cassidae).

Another interesting dead snail shell will be this Frog snail shell (Bufonaria sp.).

This longish and spiny looking shell yet also occupied by hermit crabs are quite commonly found on the Tanah Merah sandflat. They belong to the Rare-spined murex snail (Murex trapa).

And that's not all, there is another dead shell with hermit crab and it is the Japanese bonnet snail (Semicassis bisulcatum). All the above three snail species were seen live before in our shores too, though occurence were rather rare. As mentioned, this could be due to the fact that most of these gastropods tend to be hidden by burrowing into the sand.

Nevertheless, one can still find living snails ike this drill!

And also this living Spiral melongena (Pugilina cochlidium) was also spotted.

Other than snails and hermit crabs, there was a couple of wormy find!

First will be this cute little peanut worm (Phylum Sipuncula). In the past, peanut worms were once so plentiful in Singapore that they were collected and fed to ducks.

The second wormy find will be this Acorn worm (Class Enteropneusta). The worm itself is in yellow in colour and what it is doing is that it is excreting coils of processed sediments by sticking out their rear ends at the surface of the sand. What they do is that these worms swallow mud and sand and process these for edible bits. After which, excretion takes place!

The different colours of the sand seen here suggest that the deeper sandflat is more anoxic or with a different and darker substrate.

Only one type of sea cucumber was seen today, and that will be a couple of the Smooth sea cucumber.

Tiny brittlestars was also sighted, this time by James on an orange sponge.

There were some fishes swimming around and most were difficult to photograph. This rare shot I got is a shot of a juvenile Rabbitfish (Family Siganidae).

And I managed to sort of chased and took a photograph of this nice-looking and cute Gold-spotted mudskipper (Periophthalmus chrysospilos). It was solo and I didn't see any other mudskippers.

Ivan had an interesting encounter with the Blue-spotted stingray (Dasyatis kuhlii) and Collin also saw many other fishes as well. :-)

Last but not least, the special find of the day for me will be this pair of Spotted moon crab (Ashtoret lunaris).

The larger moon crab was using its claw to hold on to the claw of the smaller one. This seems to be a sign of mating.

What is disturbing today will be the top layer of oil patches that came in with the incoming tides. And we smelled something wrong as well. Was there an oil spill or a bad discharge from somewhere?

Though reclaimed shores are probably not as glorious as the now-non-existent buried natural shores, what is done is already done. Let's just leave them alone by not introducing anymore impacts and life will reclaim the dead shores again to make it to a beach which is living and exciting to visit!

More photos from today's trip in my Flickr gallery.


ts said...

It is a sign of mating. The bigger will grab on to the female during this ritual after which the female will go into its final moult and copulate.

If I rem correctly, the study was done on a different species but well the behaviour seems to be similar.

ts said...

Sorry, got a typo there, gee... I mean the bigger male.

Ria Tan said...

Wow, nice to hear about those tantalizing snail shells. We just have to keep a watch on this shore too!

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