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Flying crabs and flailing birdmen

Swimming crab, Liocarcinus depurator, swimming in mid-water. This crab is also known as the harbour crab, blue-legged swimming crab and sandy swimming crab. Colin Munro Photography.

All the images in this blog are available to license.  To view a gallery (license images or purchase prints of) these, and more of my North east Atlantic marine invertebrate images go here.  Alternatively you can search all my online stock images at my www.colinmunro.photoshelter.com  site through the search box (top right) here or on my main website here.  swimming crab images, Liocarcinus depurator images, necora puber images, stock images.

Flying crabs
A crab is neither the most graceful nor aerodynamic creature in the sea.  Okay you probably knew that already.  At first glance it does not appear to be designed for flight, its squat, angular body, entirely encased in a thick, heavy shell.  A crab attempting to fly would seem as sensible as attempting to run a marathon wearing a suit of armour.  But then, as anyone who has watched the London marathon will know, people do attempt – and succeeded  – in running marathons in suits of armour.  So why shouldn’t crabs fly?

I have been a little loose with the term ‘fly’; okay, they fly underwater.  They are collectively known as swimming crabs.  This group includes such species as the blue crab (Callinnectes sapidus) which is found around the coasts of North and South America, the red-eyed and fearless velvet swimming crab (Necora puber) that is common on shallow rocky reefs around the coast of UK and much of Europe, and the blue-legged swimming crab (Liocarcinus depurator) also common in shallow waters around UK and Europe but preferring sandier areas.

A velvet swimming crab, Necora puber (previously known as Liocarcinus puber) adopts a defensive posture as it moves across a maerl gravel seabed. Colin Munro Photography.

the distinctive wild red eyes and aggressive posture of a velver swimming crab (Necora puber). Note the broad swimmerets. Image No. MBI001256

A common feature of all these crabs is the adaptation of the fifth walking leg for propulsion through the water.  Crab legs are mostly fairly spindly affairs, ending in points on which they tippy-toe across the sea bed.  The final articulated segment of swimming crab legs is flattened and splayed into a paddle shape.  Additionally they are edged with long thick hairs, effectively widening the paddle blade.  These swimming legs are known as pleopods (from the Greek plein, to sail or to swim, and pods – legs) or swimmerets.

Swimming crab, Liocarcinus depurator, swimming in mid-water.  This crab is also known as the harbour crab, blue-legged swimming crab and sandy swimming crab. Colin Munro Photography.

Swimming crab, Liocarcinus depurator, swimming in mid-water. Image No. MBI001254.

I started this by stating that crabs were not really designed to fly (or swim for that matter).  This is true.  Swimming marine creatures conjures up images of graceful fluid movements.  That is not swimming crabs.  Generally swimming crabs swim when disturbed, as a means of escaping real or perceived danger.  They launch themselves off the seabed, flailing wildly as if convulsing through being wired up to high voltage electricity.  For seconds, or at most a few minutes, the crab will move erratically through the water.  As it tires its legs will slow; the crab will drift back down to the seabed, to scuttle away hopefully haven shaken off its pursuer.

Swimming crab, Liocarcinus depurator, swimming in mid-water.  This crab is also known as the harbour crab, blue-legged swimming crab and sandy swimming crab. Colin Munro Photography.

Close up of a swimming crab, Liocarcinus depurator, swimming in mid-water. Image No. MBI001254CP2

Watching a crab frantically waving its legs in an attempt to defy gravity, as it descends inexorably back to solid seabed I am always struck by the uncanny resemblance to another quirky British tradition (apart from wearing ridiculous costumes for marathons) that of the birdman competition.  This is an annual event held in several seaside towns, most notably Bognor Regis, where the great British eccentric emerges to don one-piece stripey swimsuits, circa 1900, batman masks, vinyl capes and wings that appear to be constructed from broom handles and ostrich feathers.  Suitably attired they launch themselves off the end of the town jetty.  Arms flaying wildly in an attempt to defy gravity (now you see where I’m coming from) they perform a graceless parabola and they too, descend inexorably to the sea below.

The first birdman competition (according to Wikipedia) occurred in Selsey, West Sussex, in 1971.  How long have crabs been launching themselves off the seabed, attempting to escape the limitations imposed by a million years of evolution, no-one knows.  Perhaps they have been sitting, half-buried, on the seabed, watching and pondering on ill-designed creatures in strange garb plunge in to the sea as they attempt to escape their own limitations.  Perhaps flying crabs are a recent phenomenon, the dreamers inspired by eccentrics in sleepy seaside towns.

Common Dolphins, mother and calf

Common Dolphins, mother and calf
Mother and calf common dolphins (Delphinus delphis) swimming in close harmony. Colin Munro Photography. Image No. MBI000335.

Mother and calf common dolphins (Delphinus delphis) swimming in close harmony. Image No. MBI000335.

 These pictures were taken during a recent trip to look for blure sharks (Prionace glauca) off the north coast.  Although we did find one blue, we had no luck with pictures (next time!).  However we did come across a large group of common dolphins (Delphinus delphis) feeding.  Each summer substantial numbers of commons dolphins can be found around the coasts of Devon and Cornwall as they follow the mackerel shaols.  Hopefully I’ll be adding to these images this summer.  As ever, these images can be licenses for reproduction and are also available as fine art prints.  Email me , telling me the image number and what you require for further details. You can also search for additional images either from my main website homepage or using my Photoshelter website. Links for both are given in the sidebar.

Common dolphins (Delphinus delphis) swimming, showing tooth rake marks on back. Colin Munro Photography, Image No. MBI000333.

Common dolphins (Delphinus delphis) swimming, showing tooth rake marks on back. Colin Munro Photography, Image No. MBI000333.

 

Common dolphins (Delphinus delphis) swimming, head on. Colin Munro Photography, Image No. MBI000339.

Common dolphins (Delphinus delphis) swimming, head on. Image No. MBI000339.

 

Common dolphin (Delphinus delphis) swimming at high speed. Colin Munro Photography, Image No. MBI000337.

Common dolphin (Delphinus delphis) swimming at high speed. Image No. MBI000337.