Discovery @ Chek Jawa on 23 Dec 2007

Thirty ninth Discovery posting:

(Entry @ 28 Dec 2007: Correction for the ID for seventh 'discovery', thanks to Ria for pointing out the mistake)

My back was still a bit aching after yesterday's (22 Dec) clearing net session at Belayar Creek, Labrador. However, it would not stop me from being able to go to Chek Jawa Inter-tidal area for the first time!

But first we were to gather at the Ubin Volunteers Hub and at there, Ron spotted a caterpillar, first 'discovery' (picture below). However, after a little picture search here and there, i am still unable to ID this, could someone help me? Thanks!
Very soon, we headed out to Chek Jawa and we made a short walk around the mangroves on the boardwalk before heading down the stairs to the inter-tidal area.

Here's a photo from the inter-tidal area of the boardwalk and you can see 20m tall Jejawi tower in the background (picture below).Side note:
In this posting, i'm not going to list everything i saw but i'll show some rare finds and try to introduce everyone to the echinoderms i saw, i'll also try to explain what are Echindoerms.

So, what are Enchindoerms?
Discovery Note:
1. The echinoderms are a group of animals that includes sea stars, sand dollars, urchins, feather stars, brittle stars and sea cucumbers.
2. They are simple animals, lacking a brain and complex sensing organs.
3. They have a water-vascular system (humans have a blood-vascular system) which pumps water through the madreporite.
4. The madreporite is an opening used to filter water into the water vascular system of echinoderms.
5. And they have tube feet which they use to attach to objects, for protection, as well as to obtain food.
6. They have radial symmetry and most can regenerate lost limbs.

The first echinoderm of the day is a sand dollar (picture below). Second 'discovery'.
Discovery Note:
1. Sand dollars belong to the same class as sea urchins, class Echinoidea.
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.

Third 'discovery' is a brittle star which is another example of an echinoderm (picture below).
Underside of the brittle star (picture below)
Discovery Note:
1. Brittle Stars belong to the class Ophiuroidea.
2. Related to and like the sea stars, they have five arms and a central disc.
3. 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.
4. Brittle stars use their arms for locomotion. They do not, like sea stars, depend on tube feet.
5. 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.

Fourth 'discovery' is a rare sight which i've have been lucky enough to see it at Changi beach recently. A bubble shell or headshield slug, a Hydatina amplustre (picture below).
Discovery Note:
1. The front of the head shield is developed into a pair of tentacles on each side.
2. It has a shell with alternating pink and white spiral bands, separated by narrow black lines.
3. Worms are part of its diet.

Fifth 'discovery' is a 'naked' hermit crab (picture below). However it was dead when i found it. =( It had probably died due to an attack from a predator when it's inside its home (an empty shell) or when 'naked' thus making it an easy target. Lesson of the day:
Don't pick sea shells from the sea shores , thus hermit crabs will have homes to live in.

Class Asteroidea of the echinoderms refers to the sea stars. And sixth 'discovery' is a sand star (picture below)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.

Seventh 'discovery' is a sea star that i've seen with my own eyes for the first time, a cake sea star (picture below)!

Entry @ 28 Dec: ID for this sea star should be Gymnanthenea laevis.Discovery Note (Updated):
1. Large block-like superomarginal plates define the border of this sea star.
2. Notable features of the upper surface are prominent spine-like tubercles on the central radial plates and sometimes it can be found on some of adjacent plates too.

Another class of echinoderms, the Holothuroidea refers to the sea cucumbers. And eighth 'discovery' is one sea cucumber, this is probably Colochirus quadrangularis (picture below). Discovery Note:
1. This is a small sea cucumber. Often less tan 10cm in length.
2. It has bushy tentacles that are used to strain plankton and suspended organic particulates from the water.

That about warps everything up. And we were quite lucky today as it only started to rain cats and dogs after we got on the van back to the jetty on Ubin.

Would like to thank Luan Keng for making this trip possible + the kuey and everyone else for coming along today! =)

Reference:
David J. W. Lane & Dider Vandenspiegel. A Guide to Sea Stars and other Echinoderms. Singapore Science Center, 2003.