By Gloria Seow, Education Committee Vice Chairperson
We gathered bright and early on 8 June 2019 at Changi Beach. Uncle Marcus Ng was our guide, assisted by Auntie Lena Chow. As advised by Auntie Gloria, all of us were togged out in covered shoes. Uncle Marcus even came in long sleeves and pants, a precaution against vicious sandflies. We avoided the use of insect repellent as we were entering the water and it would injure marine life.
The inviting expanse of the seagrass bed, exposed by the low tide, teems with intertidal life.
It is always a delight to find the Noble Volute, a gorgeous snail with zig-zag markings on its attractive shell. Its body is largely black with orange spots. As a predator, it feeds on clams. It has a restricted range of only Singapore and Malaysia as it does not have a free-swimming larval form (conducive to being carried by sea currents). As such, the Noble Volute is vulnerable to over collection.
Even when dead, its shell is useful, serving as homes for large hermit crabs. Hence, we should not collect shells from seashores as we would be depriving hermit crabs of suitable abodes.
Tiny Biscuit Sea Stars are relatively common on the seagrass beds. Larger ones are usually found on coral rubble.
The underside of the Biscuit Sea Star has orange tube feet tipped with suckers.
White Salmacis Urchin with short and sharp spines. It feeds on seaweed. This sea urchin can quickly gather various items, including seaweed and shell, to cover itself as a form of camouflage.
A hermit crab sitting on Mermaid's Fan Seaweed. This seaweed can be eaten and is used as animal feed, fertiliser and traditional medicine.
An unidentified shrimp.
A gangly-looking Elbow Crab with enormous pincers many times longer than its body.
Green Gum Drops Ascidians clinging onto seagrass. Each 'drop' comprises many zooids embedded in a common tissue.
Our best find of the day is the Spearer Mantis Shrimp, a formidable predator. On the left is its armoured tail while its head is partially hidden. Its huge pincers are akin to that of the Praying Mantis, hence its name. As a spearer, it has sharp spines on its pincers that attack at lightening speed to impale darting prey like fish and prawns.
Miliaris Cowrie with its mantle showing. The mantle can cover the shell completely such that it resembles a sea slug. The shell is glossy smooth and not encrusted because of the enveloping mantle. As a special organ, the mantle deposits a layer of pearl-like substance, and is responsible for the cowrie's colour, pattern and shell repair. The mantle also enlarges the shell. When threatened, the mantle retracts into the shell.
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