Crabs - Information and videos

in steemiteducation •  20 days ago 

You will find them in rivers and the sea and some people like eating them.  They do not walk forward like animals and humans, but they walk sideways and they have pinchers which can hurt you if the grab you.

You guessed it, today we are learning about the crab.

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 Crabs are decapods from the crustacean family. 

'Decapods' means they have 10 legs, which the grab does. even though you will maybe count 8 - the first pair of legs are the claws and are called the 'chelae'.

A crab do not have a skeleton on the inside of the body, but it has a hard shell outside which is called an exoskeleton and this protects the soft flesh on the inside.

You will find crabs living in sea water, fresh water and on land and there are 4500 types of crabs.

  • Find pictures of at least 10 types of crabs and say where you will find them.
  • Have a look at the statement below and do some research to find out what the difference is between these animals and a 'true crab'
Other animals with similar names such as hermit crabs, king crabs, porcelain crabs, horseshoe crabs and crab lice, are not true crabs. 
  • Read more on the hermit crab here.

Although most of them walks sideways, there are that can walk forward and backwards and even swim.

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If you spot a group of crabs you will call them a 'cast of crabs'.

The male crabs will fight one another over food, a female and territory. The crabs communicate with one another by waving the pinchers or making a noise with it by opening and closing it.

The Pea Crab is the smallest known species at just a few millimetres wide. The largest species is the Japanese Spider Crab, with a leg span of up to 4 m.

                   

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  • Measure out 4 m so that you can see how big this crab is.  Also find some pictures or videos on the smallest and biggest crab.

Crabs eat plants like algae and also meat like bacteria or worms and other crabs.  This means they are omnivores. 

Some of the crab species can get rid of a limb - the same way a lizard can get rid of its tail - in order to protect it. Within a year it will grow a new limb.

Some people love to eat crabs and about 1.5 million tons are caught each year.  The crab that is eaten the most is the Japanese blue crab.

  • Do you like crab?  Do you eat any other sea food?
  • Watch the story if you are done with this worksheet.

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