01 April 2013

Hermit crab view of Changi Beach

This morning I took a really REALLY close look at the seagrasses at Changi. I was literally crawling along the entire beach.
Here's what the beach looks like from below. There were lots of Striped hermit crab (Clibanarius infraspinatus) on the shore, many had lots of little Drill snails stuck on their shells.

Here's a young Fan clam (Family Pinnidae), the shell is translucent against the morning sun.
There were several White sea urchins (Salmacis sp.) dotting the seagrass meadows. As usual, they were carrying things including seaweeds, seagrass leaves and other bits and pieces.
Although the sand bar may appear dead and lifeless, there's all kinds of animals buried beneath. Sometimes, you may see signs of them on the surface, such as these sea stars.
There were a few Sea pencils sticking out above the sand. Each stick is a colony of animals and usually only commonly seen at night, retracting into the sand during the day.
There was a bloom of Sea lettuce seaweed on the shore today. And for the first time, I noticed lots of Bazillion snails (Batillaria zonalis) on a small patch of seaweed.
Wow, this is a very large Sand collar, with my foot for scale! These stiff plasticky feeling flat coils are the egg mass created by a Mama moon snail (Family Naticidae). She produces mucus which combines with sand and hardens into this shape. Once the eggs hatch, the collar disintegrates. So an intact collar is full of baby snails!
I saw this huge slimy Naked moon snail (Sinum sp.)! My first time seeing one with a brown shell and the first time I've seen one at Changi. [Correction! Tan Siong Kiat took one look at it and said it isn't a Sinum sp. It is either Polinices melanostomoides or Polinices melanostomus. Although it does have a huge body, unlike Sinum sp., this has an operculum]
There were also many different kinds of Olive snails (Family Olividae) which started to emerge in numbers from the sand as the tide turned. Today, I also saw many large dead Hammer oysters (Malleus sp.) but only a few Window pane clams (Placuna sp.).
There were of course the usual critters of the seagrasses: Pink warty sea cucumber (Cercodemas anceps) and Thorny sea cucumber (Colochirus quadrangularis), Cake sand dollars (Arachnoides placenta), Plain sand stars (Astropecten sp.). I also saw a broken shell that might be of the intriguing Watering-pot shell (Verpa penis), which so far, I've only seen on this shore.
The entire purpose of the trip was to find samples of bryozoans growing on seagrass blades for the upcoming Bryozoan and Hydroid Workshop. Alas, after peering at what felt like nearly every blade, I only found one tiny suspicious patch on a Fern seagrasses (Halophila spinulosa).
And another suspicious patch on Spoon seagrasses (Halophila ovalis).
There were all kinds of tiny snails and scummy stuff stuck to the seagrass blades. As well as this teeny tiny baby carpet anemone (Stichodactyla haddoni)!
These 'sticks' are the bare stems of Fern seagrasses, all the leaflets having fallen off. There were large areas on the beach where this had happened. Oh dear.
The water is clear at minimum tide. Here's Needle seagrass (Halodule sp.), which is now quite dominant on the high shore.
I left as the tide came in, and the sand bubbler crabs (Scopimera sp.) were also very busy processing sand and leaving delicate patterns of sand balls on the high shore.
It was a glorious morning, fishermen were all ready to start fishing when the tide turned.
My last trip here was in Dec 2012. Changi is one of my favourite shores, rich in all kinds of a marine life.

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