03 August 2011

Creepy killer barnacles on Changi

Barnacles may seem harmless, but there are some that are insidious parasites of crabs! These gruesome parasites creep into the crab, living on it and hijacking the crab into producing their eggs!
Here's one victim of the parasitic barnacle! How do we know this?

Because of the parasite egg sacs emerging from the crab. The parasitic barnacle (Thompsonia sp.) grows through the body of the host crab like a root system. The parasite affects the crab's reproductive system such that the crab becomes infertile. The parasitic barnacle eventually produces tiny egg sacs that emerge through the crab's joints. Exhausted by the barnacle, parasitised crabs usually come to an unhappy end. Thank goodness these barnacles don't infest humans!
Changi has nice stretches of seagrasses, home to all kinds of intriguing animals.
The seagrasses are dotted with many colourful creatures. As usual, there were lots of Thorny sea cucumber (Colochirus quadrangularis), and many small carpet anemones some of which might be Tiny carpet anemones (Stichodactyla tapetum) while others might be Haddon's carpet anemones (Stichodactyla haddoni).
Also abundant today were Gong-gong snails (Strombus turturella), Window pane clams (Placuna sp.) of all sizes, and small to medium sized Fan clams (Family Pinnidae).
There were also many Swimming anemones (Boloceroides mcmurrichi), which do kind of look like seaweeds and can be overlooked. Buried in the sand were a few Peachia anemone (Peachia sp.), all with white body columns. I didn't see any other kinds of sea anemones today. I saw some sea pencils and a few cerianthids (Order Ceriantharia).
Here's another carpet anemone with sea cucumber in the midst of the seagrass meadow.
I continue to see many T-shaped hammer clams (Malleus sp.) here. These animals are bivalves, the hinge is on the T-shaped part. This one had a chiton on it!
The chiton is also a mollusc! This is more obvious when we look at the underside. Like many snails, it has a broad foot.
I found the empty shell of a Watering pot shell (Verpa penis) which was originally thought to be extinct in Singapore. Marcus later found another empty shell. Looks like they are still very much alive on Changi!
This strange animal is not a worm. It is actually a mollusc and actually a bivalve or clam. There are two tiny oval shapes which are all that remains of the two valves of this strange bivalve.
While I saw some Cake sand dollars (Arachnoides placenta), I didn't come across any Pink sand dollar (Peronella lesueuri) today, except one dead one. I thought I saw some White sea urchin (Salmacis sp.) in deeper water, but I didn't see any on the higher shore. Strangely, neither Marcus or I saw any sea stars. We also did see any seahorses.
Today the tide wasn't very low and was late, i.e., at sunrise. So perhaps this is why we didn't see as many animals as we did earlier this month.
Some parts of the seagrass meadows were covered in a layer of brown scummy growths. But the seagrasses seem generally alright. There seems to me to be a lot of Needle seagrass (Halodule sp.), almost as much as the Spoon seagrasses (Halophila ovalis).  The Fern seagrasses (Halophila spinulosa) was sparse today.
Today we didn't come across any driftnets as we did on our previous trip here. I hope the shore keeps well until we get a chance to visit it again.


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