Sunday, March 7, 2010

A Walk into the Mangroves

112th Discovery Posting:

About 2 years ago, I attended a sharing session on a study done on face-banded sesarmine from a professor. I cannot remember the name of the professor but I do remember that he mentioned that he studied these crabs in Mandai Mangroves. And from then onwards, I held this hope that I would get to see these crabs up close and also visit Mandai Mangroves. I never managed to catch a sight of these crabs in my mud 'dips' in mangroves and never could find out the exact location of Mandai Mangroves until today...

Today (7th Mar), with the guide of some friends, I had the chance to explore the Mandai Mangroves and find the face-banded sesarmine crabs.
Will focus more on animals this posting since I did not really take photos of plants. =D

As we walked into the mangroves, one of the first few organisms we spotted, First 'discovery' will be mangrove horseshoe crabs (picture below).
One of the misconceptions we might have about the horseshoe crab is that it's a kind of crab due to its name. Actually, the horseshoe crab is more related to spiders and scorpions. An interesting fact about the horseshoe crab is that it has existed on Earth even before the dinosaurs! And if you are wondering if that pointy tail of it is as dangerous like the tails of stingrays, you need not worry. Their tails are not for stinging but for helping themselves to flip over if they end up underside down.

If you are interested to read more about them, click here.

The second organism, a small one was first spotted by RY. It is a mangrove big-jawed spider if I am correct (picture below). Second 'discovery'.
They are spiders commonly found in our mangroves. You might not spot them as they stay motionless on a leaf or branch and their stick/branch-like appearance. Although both genders of this kind of spider has big jaws, the males jaws are particularly elongated and are equipped with a spur each. They help them in locking the jaws of the female during mating.

After about a slow walk into the mangroves, I finally come across the face-banded sesarmine crabs (pictures below)! Third 'discovery'!Their name is as such due to the bright green or blue (I think I saw yellowish ones as well) band on their faces. Very interestingly, the bands on their faces can reflect light! And a study suggests that the different colours of their bands plays a role in sexual recognition. It is reported that the males of these crabs (to be more specific: 2 species) have more intense blue facial bands while the females have more green facial bands.

To read more about them, click here.

In conclusion, Mandai Mangrove is a really nice mangrove where you can find a great number of crabs and a number of mangrove plants (including rare ones). However, it is not for the average urban dweller, as you will get really muddy and even sink then stuck in the mud at times. And of course, the stink of mud after the trip and mosquito bites. All other things aside, it is a great mangrove. =D
Thanks to everyone who made it for the trip. I bet all of us had a nice and muddy time! =P

Tuesday, March 2, 2010

Semakau over the last weekend of Feb

111th Discovery Posting

It has been a mini hiatus from blogging recently and now I'm back!

On this recently passed weekend, I visited Semakau twice for two different reasons. Both were for Project Semakau, however the Saturday trip was for a transect monitoring session while the Sunday trip was for a guided trip for schools where I was to be a hunter seeker.

This entry is a summary of some of the things which I found or saw.

First up is something which I managed to spot for 2 days in a row, the spider conch (pictures below). First 'discovery'.
Normally, it is quite hard to spot the spider conch as they are well camouflaged amongst the reefs or rubble area. Their camouflage can come from the algae growing on their shell and even sand which covers it. Once flipped over, you can see that its shell is actually really pretty. That is why people collect their shells and at the same time, people collect them for food. Additionally, places for them to live in are hard to come by in Singapore now due to development. So due to these reasons, they are now considered uncommon in our waters.

Another uncommon marine organism in Singapore is the knobbly sea star. Semakau is one of the few places where one can find a significant number of them. Here are some of the knobbly sea stars I saw on Saturday (picture below). Second 'discovery'.
The knobbly sea star's name is as such because of the knobs present on its body. It is believed that these knobs deter predators from eating them. However, fishes like the puffer fish are known to eat them.

The knobbly sea star is also somehow one of the highlights of Semakau or any other inter-tidal walks. This is because they can grow up to about a width of 40cm wide, so they can be a 'BIG' star.

Beside the knobbly sea stars, you can also find cushion sea stars on Semakau. Here are some juveniles (picture below). Third 'discovery'.
Here's a 'adult' sized cushion star (picture below).It's always a joy to see a big cushion star as they are more commonly seen by divers in deeper waters. For the juveniles, they probably like to hide in the seagrass area before moving deeper into the reefs once they are of the right size/'age'. They have been reported to feed on organic particles found in the sediments, immobile animals and even on corals.

And of course, not to forget the common sea star (picture below). Fourth 'discovery'.All sea stars (which I know) has a water vascular system. This is like our blood circulatory system where blood is pumped all around our body. But instead of blood, the sea stars pump sea water around their bodies. So it is best to handle the sea stars in sea water if you want to touch them.

The last thing I wish to write about is this nudibranch which I have never seen in Singapore. It's a Varicose phylid nudibranch (Phyllidia varicosa). Fifth 'discovery'.The phylid nudibranchs are said to be one of the most toxic nudibranchs. It is said that if they are stressed or feel endangered, they will release a toxic chemical into the waters near them. This toxic can kill a whole fish tank of fishes if ever released into one. So to be on the safe side, don't ever handle this nudi.

That's about warps up this posting. Thanks for reading and everyone who were on the trips on both days for making it another great weekend out.

1) KS's entry for the Sunday trip: