I saw a little Masked Crab (Corystes cassivelaunus Pennant) on Knoll Beach at Studland the other day. It was an unusual sighting for that location. The crab was alive – but lucky to be so. It had buried itself in the wet sand to survive the rigours of exposure at low tide. There are not many other places for an animal to hide on this part of the beach.
The small crab, only a couple of inches long, would probably have stayed out of view until the tide came in again – except that this was the afternoon that several schools decided that it was just the right moment for the students to run on the beach while the sun was shining. The youngsters pounded their way along the shore and one of them stepped on the very spot where the crab was sheltering. Being disturbed by this close encounter, it surfaced, all covered in wet sand, as I walked past it and eastwards in the direction of Shell Bay.
I was surprised to see this same little seashore creature again as I made my way back along the water’s edge going westwards. I know it was the same crab because it was almost the only live thing I found, and certainly the most interesting. It was one of those days when there was not much at all newly washed ashore: a few fresh clumps of spindly red seaweed, some brown Sea Oak and strands of kelp, a few pieces of translucent green Sea Lettuce, and some clusters of Slipper Limpets. Lots of empty bivalve shells.
On this second meeting with the Masked Crab, the creature was more active and had got rid of the sand which had been covering it before. It was waiting for the waves. I have seen this activity previously in Masked Crabs on Rhossili Beach on the Gower Peninsula. The animal sits facing the sea, using its legs to brace itself against the oncoming water. Its two fringed antennae can be joined together to form a single tube and this was projecting forwards and upwards – looking very much like an angler holding a fishing rod. It was fascinating to watch the way to crab parted and then joined the antennae, moving them side to side as if using them to gauge the speed and timing of the next wave. The antennae form a breathing tube when the crab is buried.
I took a few photographs of the Masked Crab and some short video clips which you can see below. I hope that you will appreciate that it was a bit difficult to film the crab in action because of its small size and the necessity for recording it in such a low position – plus the imminent drenching of both the crab, the camera, and the photographer.
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