Rockpooling

I have not been in the water recently but went good oldfashioned rockpooling instead a week ago. No ‘lifers’ but there is always something interesting to see. For instance, my first albino cushion star (Asterina gibbosa). This small species (these individuals are only a little over a centimetre) is incredibly common here. Btw, I must confess this shot was staged, I placed these seastars together. Below, a Candy-striped flatworm (Prostheceraeus vittatus), also about a centimetre. Next, the Yellow-plumed or Side-gilled seaslug (Berthella plumula). Another common species but it is difficult to get a decent photo of this blob! This mollusc has an internal shell and, interestingly, glands that secrete sulphuric acid when it is attacked. You can see a little slug right beside it, maybe a juvenile Sea Lemon. Berthella plumulaFinally a photo that I had wanted to take for a while: can you spot the crabs? One of the most common invertebrates here is the Furrowed Crab or Montagu’s Crab Xantho incisus. Xantho species are known as Pebble Crabs which is the name I prefer; although highly variable in colouration they are very good at blending in amongst the pebbles! How many can you spot? There might be a stray Risso’s Crab Xantho pilipes in there as well, as they are quite similar (except for a fringe of hairs on the legs and carapace) and also common here. High time to have a look again underwater as well.

hairy crab

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This weekend I stopped by Castle Beach in Falmouth to release some of my Snakelocks anemones (more about the aquarium in a next post…). Although the weather was bad, of course that did not prevent me from turning over some rocks. My curiosity was rewarded with another new find: a Hairy crab Pilumnus hirtellus. A beautiful little crab which is not uncommon but here it definitely is not as ubiquitous as the Furrowed and Edible crabs:

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I also found a Furrowed crab Xantho incisus with unusual coloration (perhaps because it had moulted but I did not check):

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low tide

The tides were good this weekend and so we went out to Gylly (Gyllyngvase) Beach in Falmouth, specifically the rocks to the west of the beach (I normally go to Castle Beach to the east):

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Although the tide was quite low, no special sublittoral species were encountered, but everything time you go out you still see something new. For instance, a newly moulted Furrowed crab, Xantho incisus pink and soft next to its old brown carapace: IMG_5469

There were very many small Blue-rayed limpets Helcion pellucidum (see also here) on the kelp:IMG_5412

A tiny Rissoa parva snail:IMG_5409

and a Painted top shell Calliostoma zizyphinum:IMG_5457

Some dark green Cladophora rupestris:IMG_5437

A fine red seaweed (I do not know which one) growing on top of Dulse Palmaria palmata growing in turn on top of kelp: IMG_5455

Three crabs

The diversity of crabs here in Cornwall is quite high: it is easy to spot more than five species in just a minute of rock pooling. The Furrowed crab Xantho incisus (or X. hydrophilus) has relatively large claws and can do a lot of posturing when disturbed but it is actually quite docile and never pinches hard:

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I have only once encountered the small crab Pirimela denticulata (but I must say I have not been looking particularly hard):

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The Broad-clawed porcelain crab Porcellana platycheles is extremely common under rocks. I have added a couple to my aquarium when I started but as they just hide under rocks that wasn’t a very smart idea. Months later when re-arranging a rock I found them again so at least they seem to do well in the aquarium:

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