An empty Common Spider Crab carapace

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Spider Crab shell: An empty Common Spider Crab carapace, outer surface with spines, tubercles, and orange-red pattern, from the strandline at Studland Bay, Dorset, UK - part of the Jurassic Coast (1) 

I think this empty Common Spider Crab carapace (Maja squinado (Herbst.) is particularly pretty. It has been moulted by the animal which has outgrown its shell. Crab shells like this are a very common find on the strandlines of beaches. I found this one at Studland Bay in Dorset. It is a rather small carapace, only about 70 mm maximum, so a young individual. A large mature specimen would have a carapace 200 mm long by 150 mm wide.

The circular, convex shell is edged with strong tapering spines, with shorter, blunter spines and tubercles or bumps over the general external surface. This rough, spikey, outer layer is also covered with a brightly-coloured, irregular and abstract pattern in hues of red, orange and brown. Older crabs decorate and camouflage themselves by attaching pieces of weed, sponge and other sedentary organisms to the shell  – but this one is still clean and lacks any encrustation. 

The inside of the carapace is a real contrast to the outside. It is smooth, glossy, and white. Numerous pores or holes form an overall network. There is a pattern which is difficult to define. Maybe the pores relate to the spines and tubercles above. This internal layer is slightly translucent and almost like porcelain in texture when viewed normally. However, if the shell is held up to the light, the white inner layer seems to become transparent, so that the red patterns on the outer surface become hazily visible. 

Spider Crab shell: An empty Common Spider Crab carapace, outer surface with spines, tubercles, and orange-red pattern, from the strandline at Studland Bay, Dorset, UK - part of the Jurassic Coast (2) 

Spider Crab shell: An empty Common Spider Crab carapace, outer surface with spines, tubercles, and orange-red pattern, from the strandline at Studland Bay, Dorset, UK - part of the Jurassic Coast (3) 

Crab shell close-up: Close-up detail of the colours, pattern, and texture on the outer surface of an empty Common Spider Crab carapace from the strandline at Studland Bay, Dorset, UK - part of the Jurassic Coast (4) 

Spider Crab shell close-up: Close-up detail of the glossy white inner surface of an empty Common Spider Crab carapace with its network pattern of pores, from the strandline at Studland Bay, Dorset, UK - part of the Jurassic Coast (5) 

Spider Crab shell close-up: Colour, pattern, and texture on the inner surface of an empty Common Spider Crab carapace when viewed with back illumination causing transparency of the normally opaque white inner layer. Specimen from the strandline at Studland Bay, Dorset, UK - part of the Jurassic Coast (6) 

Revision of a post first published 16 March 2010

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11 Replies to “An empty Common Spider Crab carapace”

  1. It does look rather like a creature one might find in a sci fi film, or Star Trek, doesn’t it? I’ve never seen one in real life, or found an empty shell like this but I guess that’s just chance.
    Is spring arriving now in Dorset? Suffolk is showing signs of spring finally but it’s still quite cool. We’re having our windows double glazed so the nice weather this week is a bonus; no shivering while the guys work!!

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  3. Hi, Viv. I suppose it does look a bit weird and wonderful. With legs it would look more so. It’s funny how I imagined that these were a common sight on every coast just because I see a lot of them on the south coast and Gower. I have seen great massings of live spider crabs in pools at the base of Worms Head. It think they were mating congregations.
    Spring is very slow in arriving here in Dorset. It’s been a lovely day with blue sky and sunshine but still cold. A few snowdrops and daffodils but barely a leaf bud showing green on the trees – just a few catkins and pussy willow. This has been the coldest winter I can remember for a long time.

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  4. Hello, Linda. The words are more difficult to manipulate than the pictures – so thank you for saying that you enjoy the descriptions in the text as well.

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  6. I like the deep red too but I think that the shells of the crab family (including the common edible crab, for example) are often that colour if not such a deep shade, which may be just found in immature specimens. Older common spider crab shells are frequently covered with so much detritus that it is difficult to see their proper colour at all – they just look vaguely orange.

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  7. I’m with Linda on this; your descriptions are super too. No nonsense and strangely poetic; can’t put it any better than that.
    Yes, a long cold winter, longer and colder than any i can remember. But my sap is starting to rise as the days lengthen.

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  8. Thank you for that, Viv. May the greenhouse effect of your new double glazing make your sap rise fast.

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  9. Pingback: Jurassic Coast – Posts about Studland Bay – Jessica's Nature Blog

  10. The other day I found a shed spider crab shell and photographed the interior which was so beautiful – it looked like a porcelain bowl with its delicate shade of blue and the abstract pattern of holes and dimples. I looked on the internet to see if there were similar images and found ONLY yours – which amused me because I am already a fan of your photos. I can’t believe that no one else appears to have taken taken similar shots. Thank you for what you do.

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  11. That is strange. It is rare to be unique with images on the internet. We are obviously drawn to the same natural kinds of beauty. They say great minds think alike!

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