Thursday, February 12, 2009

Baby horseshoe crab at Pasir Ris

Yesterday evening I was at Pasir Ris Beach. Though this shore has been visited several times, there are still surprises awaiting for us to discover.

A baby horseshoe crab (Family Limulidae) was found by Chee Kong. And it is as small as about 6mm! I have never seen such a small one before.

Even the tail of the horseshoe crab is only beginning to grow out of its exoskeleton. This tiny creature swam short distances using their swimmerettes and gill flaps. Very exciting!

Chee Kong again found another horseshoe crab and though it is much larger as compared to the 6mm one, this horseshoe crab is still considered juvenile as compared to their full size as an adult.

Asian date mussels (Musculista senhousia) were much more abundant this time as compared to previoys trips. They form mats over the shore through their byssus threads which act to trap sediments. This eventually forms the mats of mussel beds. Each bivalve looking thing in this photo is an individual mussel embedded on the substrate (except for the one above).

For the first time, I photographed the mussels filter feeding in action.

The structure that this Asian date mussel used to filter feed is very intricate and this is the first time I noticed it. Such is the beauty of tiny creatures if you bother to look real close.

There were also many more plain sand stars (Astropecten sp.), probably a response from the increase of mussel bed coverage.

There was also another special find of this juvenile cake sea star (Anthenea aspera) which made my day on top of the cute baby horseshoe crab. :-)

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