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Sea Shore

Edible Crab - topsideEdible Crab
The top of the carapace (shell) is a reddish brown or purple colour.  The front edge of the carapace looks like the pinched edge of a pie crust.  The large claws have distinctive black tips.  Larger edible crabs are found in deeper water, the ones you find in rockpools are normally much smaller

 

Edible Crab - Underside Edible Crab
The underside of the crab is much paler.  The crabs abdomen is curled under its body.  The shape of the abdomen can be used to determine the sex of the crab.  The crab in the photograph is a male, his abdomen is very long and narrow.  Females have a much broader abdomen.  The female crab carries her eggs under the abdomen where they form a distinctive mass.

 

Velvet Swimming Crab Velvet Swimming Crab
This crab is named for the soft velvety hairs which cover the carapace on the crabs back.  It is the most aggresive of the British shore crabs, this coupled with its bright red eyes have given it the alternative name of Devil Crab!  If it is disturbed it will raise its claws in aggressive threat.  This is not bravado, it is very capable of giving a painful nip.

 

Velvet Swimming Crab - Hind leg Velvet Swimming Crab
The back legs of the Velvet Swimming Crab are modified into flattened paddles which it uses to swim through the water.  Despite its swimming abilities it is normaly to be found hiding under rocks.  A large Velvet Swimming Crab is about 8cm across, but most are smaller.

 

 

Hairy Crab - Topside Hairy Crab
This is a small brownish crab, rarely more than 2cm across.  It is covered in hairs all over, giving it its common name.

 

 

 

Hairy Crab - Underside Hairy Crab
In this species of crab one claw is normally much larger than the other.  The abdomen of the crab is visible in this photograph.  The narrow abdomen on this crab shows it to be a male.

 

 

Hermit Crab

Hermit Crab
Unlike most crabs the hermit crab has a soft abdomen that is not covered with a protective shell.  It compensates for this by living inside the shell of a dead gastropod (snail).  This protects the crabs vunerable rear, but does not grow as the crab grows.  This means hermit crabs have to keep moving to a bigger shell as they grow.  They are very fussy about finding a suitable shell and will inspect many before they find one that is perfect.  If suitable shells are scarce they will even fight over them.  Hermit crabs are omnivores eating plant material also also scavenging the remains of other dead sea creatures.  You can spot them in rockpools when you see a snail shell move with unusual speed!  Most of the hermit crabs you will find are small and can be found in a variety of snail shells.  It can be surprising how many live in a single rock pool.

Squat Lobster Squat Lobster
Squat Lobsters are much smaller than true lobsters.  They are in fact more closely related to hermit crabs than lobsters.  They can be easily identified by their very long front pair of legs and their flattened bodies.  When disturbed the squat lobster rapidly flaps its tail, which is normally kept tucked under its body.  This can propel it rapidly away from danger, but is less efficient in very shallow water!

 

PrawnPrawn
Small prawns are common in rockpools but are easily missed due to their transparent bodies and rapid movement.  They can often be caught with nets just by trawling among the seaweeds in the larger pools.  On rocky shores, like those at Lyme, prawns are more common than shrimps.  Prawns have an extension at the front of the head called a rostrum.  In prawns this has a serrated edge (visible in the photograph).  Prawns can grow to 10cm in length, but those in rockpools are much smaller.  They are important as food for other larger seashore creatures.

RagwormRagworm
These animals are found buried in mud under stones or holes in the shale.  They have long flattened bodies which are divided into segments.  The colour of ragworms is very variable from browns through reds and even shades of green.  Ragworms have powerful jaws and are efficient scavengers and hunters.

 

 

 

Beadlet anemone Beadlet anemone
This sea anemone comes in a variety of colours from reds to orange/brown and green.  When the tide is out it can retract it's tentacles and become a blob of jelly.  This reduces the surface area of the sea anemone so it looses less water by evaporation.  Like many creatures that live on the shore it is also very tolerant of changes in temperature.

 

Snakelocks anemone Snakelocks anemone
This sea anemone can be found in two colour forms.  The most easily spotted are bright green with a purple tip to the tentacles.  The bright green colour comes from a green algae that lives inside the tentacles.  The algae benefits the sea anemone by making food from sunlight by photosynthesis.  The algae also benefit from this arrangement.  Two organisms living in a mutually beneficial way like this is called symbiosis.  To benefit from the algae the Snakelocks anemone likes to live in shallow brightly lit water.  Some anemones have no algae and they are more of a dull grey colour.

Netted whelk Netted whelk
This gastropod (snail) feeds mainly on other dead marine creatures.  It is ver y common in the rockpools around Lyme Regis.  It is closely related to the carnivorous Dog Whelk.  The shell has a reticulated (net-like) pattern on the surface which has given the species its name.  In the photograph you can see the tube the whelk uses to breath through when it is buried in sand.

 

Limpet Limpet
Limpets are gatropods, but they do not have the usual coiled shell of a snail.  Instead they have a distinctve conical shell and can be found attached to hard rocks and concrete breakwaters all over the shore.  They normally attach to sheltered places in crevices or on the edge of rocks.  This protects them from being swept away by strong waves, eaten by predators or dried out by the sun.  When you see a limpet attached to a rock you will often see that it fits snugly into a hollow in the rock below it.  This hollow is called a scar and was created by the limpet grinding its shell on the rock.  This wears away the limpet's shell and the rock, creating a perfect fit between the rock and shell.  This is important as it potects the limpet from dessication and predators.  Limpets are herbivores, feeding on the algae on rocks.  They scrape it off the rocks using a rough tounge called the radula.  You can sometimes see strange patterns on rocks which are the feeding tracks of limpets.  Limpets compete for attachment space on rocks, not only with other limpets but also with barnacles and seaweeds.  This limpet has barnacles living attached to it's shell.