Sunday, July 15, 2007

Discovery @ Changi Beach on 14 July 2007

Sixteenth Discovery Posting:

(Entry @ 16 July 2007: New information about the moulting of crabs and Update of facts thirteenth 'discovery', thanks to Ron for the info)

What were you doing on Saturday early morning at 3am?

Catching a late night movie? Partying at a night spot? Sleeping?

But some Semakau guides and i were at Changi Beach doing exploration along the shoreline during the low tide.

And the first thing that caught our eyes when we stepped on the shoreline was this green 'thing' covered with sand, what was it?

A flip and the answer was revealed. A turtle~

To be more specific, a teenage mutant ninja turtle (picture below)! Hahaha. What was this doing there? Looking for the other three ninja turtles? =p
Anyway, the first 'discovery' of the 'morning' was a stripped hermit crab (picture below).
Discovery Note:
1. I haven't seen this kind of hermit crabs on our southern shores before. I wonder is it 'native' to our northern shores.
2. Empty Sea shells are potential homes for hermit crabs, so please don't pick any shells from the seashore.
3. To quote from a famous tongue twister, "Sally sells seashells on the seashore.", we say, "Don't buy the seashells Sally sells on the seashore" =)

Within a few steps away in the sand was the second 'discovery', a ball sea cucumber (picture below).
Discovery Note:
1. They are seldom seen as they are buried beneath the sand.
2.They are sometimes washed ashore among piles of seaweeds, so try not to step on seaweeds during inter-tidal walks or keep your eyes wide open.
3. And remember to put them gently into a pool of water if you see an exposed ball sea cucumber.


As we squatted down to take better photo shots of the sea cucumber, we looked around the sea grass around our feet and found that there were a number of 'baby' brittle stars measuring about 2 cm in diameter (picture below). Third 'discovery'!
Discovery Note:
1. Related to and like the sea stars, they have five arms and a central disc.
2. As the name suggests, the arms of the brittle stars are rather liable to break. This is actually an escape mechanism. They can regenerate their arms, but slowly.
3. Brittle stars use their arms for locomotion. They do not, like sea stars, depend on tube feet.
4. Brittle stars move fairly rapidly by wriggling their arms which are highly flexible and enable the animals to make either snake-like or rowing movements.
5. Brittle stars can reproduce asexually by self-division.

6. Just brought a book on sea stars, so if i'm not wrong, this should be the Ophiothrix fumaria.

Walking on, someone soon spotted a sand star (picture below). This is the fourth 'discovery'.
Discovery Note:
1. The tube feet of sand stars end in points instead of suckers.

2. These pointed tube feet push down powerfully allowing Sand star to ‘race’ rapidly over the sand and burrow quite quickly.


Ron soon then spotted a pair of moon crabs, doing their bit for nature... mating (picture below). =P Fifth 'discovery'! But as soon we got close, the male moved away from the female. Did we disturb them? Oh, i hope not...
Discovery Note:
1. Instead of the usual walking legs we see on crabs, all four pairs of legs of the moon crab are paddle like.
2. This helps the crab to swim and used as spades to quickly bury themselves into the sand.

I do wonder if the moon crabs swim faster than swimming crabs since they have 8 'paddles' instead of 2 that swimming crabs have. Can anyone enlighten me?

After reading TC's blog, he mentioned that on a new moon, loads of crabs would moult. It was quite true as the night had a new moon and there were loads of crab moult along the inter-tidal zone. And we were lucky enough to see a newly moulted crab (picture below). Sixth 'discovery'~

(Entry @ 16 July 2007: More crabs are known to moult during full moon nights.)
Discovery Note:
1. Did you know that soft shell crabs that some of us eat are actually crabs which just moulted?

A pipe fish (picture below) was the seventh 'discovery'.
Discovery Note:
1. Pipe fishes belong to the same family as the seahorses and have similar practices and diet.
2. Like the seahorse, the male pipe fish carries the eggs.
3. Pipe fishes lack a pouch, so the eggs are glued to the underside of a male's tail or abdomen.

As I slowly walked with my feet in the water and trying my best to spot things and not to step on anything alive, Luan Keng called
out to me and told me they spotted a flat fish! I haven't seen it with my own eyes before. So here is it (picture below). Eighth 'discovery'! Discovery Note:
1. The larval flatfish has its eyes and mouth located in places just like other fishes. But as it develops, one eye and the mouth move to the upper side of the fish.

2. Being flat, they can lie just beneath the sand with only their eyes sticking out, while they ambush to wait for their prey (bottom-dwelling worms, clams, crabs and shrimps) to appear.

After photographing the flat fish, i continued my exploration and soon spotted a sea pen (picture below). My first sighting for this, okay, this is the ninth 'discovery'.
Discovery Note:
1. They got their common name due to their resemblance to feather quill pens.
2. A single sea pen is actually made up of many polyps, just like corals.

3. By the way, they are cnidarins like corals and jellyfish.

Further exploration then yield sightings of a number of sea urchins
, here are 2 different ones (pictures below) and tenth 'discovery'. Discovery Note:
1. Sea urchins have sharp spines that deter most predators and us from touching them.
2. The urchins we saw were using its spines to attach sea weeds around its body to camouflage itselves.
3. The spines are actually moveable and may be used for walking.

And on a sandy part of the zone, Ron spotted a geographic sea hare (picture below). Eleventh 'discovery'.Discovery Note:
1. They are often overlooked as their appearance enables them to blend in with the seaweeds or they may lie buried in the sand.
2. They can swim by flapping the sides of its body.

Twelfth 'discovery'
was a moon snail with its body expanded outside its shell (picture below).
Discovery Note:
1. Moon snails are able to inflate its body with seawater as it emerges from the shell and the fully expanded body can be much bigger than its own shell.
2. The Moon snail is able to warp its huge body around its prey to suffocate it.
3. It can also secrete an acid to soften its victim’s shell. A hole is then eventually created in the shell with its radula.
4. The Moon snail generally feeds on snails and clams.

A little while after i wondered away from the moon snail, TC called out to me and asked to check out something. Oh, from the looks of it, a new moon night isn't only great for moulting but also mating (picture below). haha. Thirteenth 'discovery'.

(Entry @
16 July 2007: The two flower crabs are not actually mating, the male crab was probably guarding the female, waiting for her to molt before they can mate. Thanks to Ron for info again) Discovery Note:
1. The male should be the smaller crab.
2. In nature, at times, the males are smaller than the females and maybe more 'attractive' in appearance than females.

Fourteenth 'discovery'
was something that i didn't had a great photo the last time i visited Changi beach, so here is it, discoverers, the sand dollar (picture below).Discovery Note:
1. Sand dollars are echinoderms, in short, they are related to the sea stars.
2. Living sand dollars are coated in fine, harmless spines that made them very velvety.
3. The spines are movable and are used to dig into the sand or move around.
4. The dense layer of spines also helps to keep off sand and silt so there is a flow of oxygenated water across the body.

As i shone the torch Luan Keng lend me into the water, i saw pairs of small red spot reflections. A closer look reveal these to be shrimps.
Fifteenth 'discovery' is a photo shot of one (picture below).
Discovery Note:
1. As i switched off the light to rest my eyes, i saw short bursts of green flashes coming from these shrimps. Wow, natural flash lights.

An anemone that swims. Would you believe that? Yap, i did saw one. A swimming anemone (picture below), let's count... sixteenth 'discovery'. Discovery Note:
1. This anemone often looks like a ball of tentacles and it doesn't have a long body column that is buried in the ground like the carpet anemones or peacock anemones.
2. Instead, it may be perched on seagrasess. This anemone can swim by undulating its tentacles!

There seem to be a number of anemones we saw. Here's one which most of us think that it's an anemone but not sure what is the ID (picture below). Seventeenth 'discovery'.
As we started to head back towards our starting point as the tide was coming back in, someone spotted this sand star in the process of feeding (picture below). Eighteenth 'discovery'~Discovery Note:
1. As you notice, this sand star has only four legs, but it is able to regenerate its 'missing' leg although it takes a while.
2. The part where you see some shells is where the sand star's mouth is located at.

Nineteenth 'discovery' was something out of the norm. A lady beetle on a sea grass? (picture below). Why was it doing here?Discovery Note:
1. Commonly called as lady birds or lady bugs, but scientists prefer to call them lady beetle. As they are bettles.
2. They are generally considered useful insects as many species of lady beetles feed on pests in gardens, agricultural fields, orchards, and similar places.

3. A few species of lady beetles are pests though, but they are known to be found in the region of North America and Europe.

4. Some people consider seeing them or having them land on one’s body to be a sign of good luck to come, and killing them presages bad luck.

The last thing we saw was spotted by Robert. Twenty 'discoveries', wow! A ghost crab (picture below). And it was so nice to let us take a number of photos before racing off and borrowing into the sand.
Discovery Note:
1. These crabs are called ghosts because of their ability to disappear from sight almost instantly, scuttling at speeds up to 16 km per hour, while making sharp directional changes.
2. Ghost Crabs live in deep burrows above the waterline.
3. They come out of their burrows to feed at night.
4. They are known to eat small particles of dead plants, animals, algae and micro-organisms.


It was really an eventful 'morning' for the amount of things we saw. Thanks everyone again~

So you can 'discover' that our Changi shores are much, indeed, really 'alive' but ... the sad note is that this is also a favourite site for poachers to gather marine life...

1 comment:

tHE tiDE cHAsER said...

Actually, it's observed that more crabs molt during a
full moon
, though many also molt during new moon.

Hmm... anyway, also not sure if the two moon crabs are actually mating or performing some courtship ritual, but am sure the flower crabs are definitely not mating. Flower crabs mate face to face. The male crab is probably guarding the female, waiting for her to molt before they can mate.