Children

Walk with decapods

Have you ever seen crabs waving with a claw which is absurdly large? Visit a mangrove at low tide to see one. To some people they appear to be playing the fiddle. They are the male fiddler crabs, vying for female attention. The females, of course have claws that are equal in size. The oversized claw is also used as a weapon when the male fiddler crabs wish to assert their right over a female or a dug-up hole. The claw-to-claw battle can literally cost them an ‘arm or a leg’. They may lose one or more of their five pairs of appendages, but that doesn’t matter. They can regrow the lost limb in a short while.

Crabs have an outer shell of calcium carbonate (the same stuff marble is made of) and along with lobsters, shrimps and barnacles, are grouped as crustaceans. They are found on land too, making their appearance during the monsoon. Most crabs are scavengers, living off detritus. Some eat worms, mussels, snails and others feed on aquatic plants.

Crabs in turn, are eaten by fish, turtles and octopuses. Thus they form an important link in the food chain.

There are over 4,500 species of crabs and each has its own amusing story to tell. The largest is the spider crab whose claws span a phenomenal 12 ft and the tiniest is the pea crab, barely a few mm long.

Crab stories

For some strange reason nature has not given a complete protective shell to the hermit crabs. The lower half of their body is unprotected. They are compelled to hunt for abandoned shells that fit them like a pair of trousers, to ensure they do not become easy pickings of birds. Some hermit vrabs, not satisfied with having found the right shell, seek further body guards: sea anemones. They tickle and tease the sea anemones until the latter climbs onto the crab’s shell and fixes itself there. The hermit crab obligingly gives the sea anemone free rides to places where there is abundant food and in return the sea anemone uses its tentacles to sting any squids or cuttlefish, (the hermit crab’s enemies) that may dare to approach too close for comfort.

Then comes the robber crab or coconut crab, found on the Indian Ocean islands, climbing up coconut trees and using its sharp pincers to pierce coconuts, drink up the water within and sometimes even break them open to enjoy the kernel. This notorious crab is the largest land crab.

Sometimes, while strolling on the beach, a box-like crab with horns on its stalked eyes scurries rapidly by your feet. You stop to have a closer look and hey presto! It has vanished into thin air. You have just spotted a ghost crab. Their shells being stippled brown, exactly the colour of sand, they are impossible to discern when they suddenly stop moving.

Have you ever heard a crab clapping while exploring the rocky pools during low tide at the seashore? Indeed, hiding under rocks there are clapping crabs that have a typical zig-zag border on their carapace and conspicuously-coloured scarlet legs. Every now and then they open wide their claws and bring them together, as though clapping. They clap, not to cheer their fellow creatures but to frighten away their enemies. Perhaps, if you keep your ears open you may hear them clapping too.

The porcelain crabs are not crabs at all, though when looked at head-on, they do resemble crabs to a great degree. They are probably lobsters being evolved into crabs. They have huge claws like crabs — pinkish-red with intricate patterns — but they have a pair of long feelers like all lobsters do. They only have three pairs of walking legs unlike crabs that have four pairs. Their elongated lobster-like abdomen is normally tucked in under the body. They are as delicate as porcelain and their claws or legs break off very easily. It is a common site to see them with missing limbs.

On and on we can go, the list is endless. The next time you are in a ‘crabby’ mood, just think of the many quirky crabs going about their business, that’s sure to raise your spirits!


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Printable version | Sep 25, 2021 6:21:30 AM | https://www.thehindu.com/children/walk-with-decapods/article29602667.ece

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