The South-claw Hermit Crab – Diogenes pugilator

I found this tiny hermit crab scrabbling around in the seaweed and seashell debris of a sandy tide pool beneath Rhossili cliffs. I thought at first that it was just a very small, immature, specimen of the common hermit crab (Pagurus bernhardus Linnaeus) but as soon as I picked it up for a closer look I could see that it was something special because it had a large claw (cheliped) on the left instead of the right. There is only one species with this characteristic – the south-claw hermit crab, Diogenes pugilator (Roux). The mature specimens have a greenish carapace no greater than 11 mm in length.

According to Hayward and Ryland (1998) this crab lives in fairly sheltered sandy bottoms from low water spring tide level down to 35 m, on south and west coasts of the British Isles where it is described as common. It also occurs elsewhere from Holland to Angola, Mediterranean, Black Sea, and Red Sea. Mullard (2006) provides more information, saying that D. pugilator is only found in a limited number of places in Britain and Ireland because it is primarily a warm-water species and may be worthy of further study in relation to climate change since there are signs of it extending its range. It was first recorded in Britain “at Worms Head” from specimens provided by L. W. Dillwyn of Sketty Hall in Gower to Spence Bate in 1850 who described it in Annals and Magazine of Natural History.

The crab can quickly bury itself in clean, well-sorted sand on a gently shelving moderately exposed beach facing southwest where conditions are less turbulent than on steeper beaches. This crab has an interesting extra way of gathering food, in addition to scavenging or eating sediment. While mostly buried in the sand, it can sweep its hairy antennae around in an almost circular motion as a net to capture small edible particles from the water.

South-claw Hermit Crab

References

Hayward, P. J. and Ryland, J. S. (eds) 1995 (revised edition 1998) Handbook of the Marine Fauna of North-West Europe, Oxford University Press, New York, pp 434-437, ISBN 0-19-854055-8.

Mullard, J. 2006 Gower, The New Naturalist Library, Collins, London, pp167-168, ISBN0-00-716066-6.

Pebbles at Manorbier

Brightly coloured pebbles on the beach at Manorbier in South Pembrokeshire, Wales, with patterns of reflected light under clear sparkling water in a gently flowing stream.

Coloured pebbles under water on a sunny day

Coloured pebbles under water on a sunny day

Coloured pebbles under water on a sunny day

Coloured pebbles under water on a sunny day

Coloured pebbles under water on a sunny day

Hyalophora cecropia mating

Video

A couple of years ago while I was in Nova Scotia, Canada, we stayed at a delightful bed and breakfast called the Baker’s Chest in Truro. Besides memories of the beautifully furnished house and gourmet breakfasts, the well-maintained garden had a wonderful surprise in store. The owner pointed out that a large moth had just emerged from under the decking and was drying its wings on the wooden trellis. A few hours later, there were two moths. The first had been a female and the newcomer was a male, attracted by the pheromones that she was giving out, and now the two were locked in the slow moving and elegant mating embrace that you can see in the video. They are Hyalophora cecropia, also known as the Robin Moth, and are the largest native moth in North America, with a wingspan that can reach 15 cm or 6 inches across.

Thames flood-tide current 3

Video

As the tide flows upstream near high water on the River Thames in London, the down-flowing river is maximally conflicted, resulting in interesting movement and patterns of reflected light.

Click on the pictures below for a more detailed version.

Natural abstract water patterns

Natural abstract water patterns

Natural abstract water patterns

Natural abstract water patterns

Natural abstract water patterns

 

By the River Bank 2

View looking north along the river in the Cerne Valley

The Cerne Valley is becoming lush. April has seen prolonged periods of sun and warmth spurring on plant growth. The catkins have fallen and all trees are starting to flower and come into leaf. Along the river banks, the low-growing Butterbur that had been clustered on bare dredged-out chalk heaps are now concealed by dock, stinging nettle, and flowering Comfrey. Iris and Sweet Flag stand flowerless with their roots in the water. An isolated leaf curves downwards to trail its point in the river flow, creating fantastical patterns of reflected light, while the birds sing their hearts out and bees buzz lazily by.

Stand of Yellow Flag leaves on the riverside

Leaf of Yellow Flag trailing in the water flow

Macro-photograph of reflection patterns made by a trailing leaf in a small river

Macro-photograph of reflection patterns made by a trailing leaf in a small river

View looking south along the banks of the River Cerne