Pebble Crab

Pebble Crab

In this short post, I’m going to be talking about this unknown or rare crab. I tried my best to find information about this animal. So just enjoy it.

These crabs really do resemble tiny pebbles and are sometimes seen on our Northern shores. Silty, sandy areas near seagrasses. They are usually buried under the sand.

Features: Body width 1-2cm. Body smooth somewhat rhomboid, indeed resembling a tiny pebble. The head forms a blunt pointed tip with a pair of tiny eyes. In this way, its eyes can peep out while the rest of the crab is buried underground. It has powerful long flat pincers with pointed claws. The crab can bury itself in the sand very rapidly. Some may be colourful.

The carapace of this crab is almost circular 20-25 mm wide, smooth, slaty grey with three slightly angular projections on each side. The legs are slender with chelipeds that are long and fine, especially in the male.

This species of pebble crab is commonly found among seagrass in shallow mud and sand flats across southern Australia such as in Port Phillip Bay, Western Port and Corner Inlet.

Pebble crabs can be seen burrowing in the soft mud of intertidal seagrass meadows but move about in search of food when the tide is out. They use their long chelipeds to capture small invertebrates.

According to the Singapore Red Data Book, the Rubble crab (Favus granulatus) is known only from Singapore and was a new genus and species discovered from Singapore and is not yet known elsewhere. It was found on Siloso Beach of Sentosa which has since been ‘improved’, and Pulau Semakau. Alox somphos, a related species in another genus was also first described from Singapore.
Status and threats: Some of our pebble crabs are listed as ‘Endangered’ on the Red List of threatened animals of Singapore. Like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution. Trampling by careless visitors also have an impact on local populations.

I found a random book in a library about this crab and it told me that this is the only crab in the world that could walk forwards. Normally, crabs only walk sideways because their legs are too close together.
If I’m wrong about the walking straight crab, make sure to leave a comment. Also, thank you so much for reading.

About Dan the Young Scientist

Science is my Life!
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10 Responses to Pebble Crab

  1. Well, I’m out of ideas about animals. And thank you for reading about these amazing animals.


  2. scifihammy says:

    A very interesting and informative post. I didn’t know any crabs could walk forwards either.
    There was something I saw about crabs a while ago – I think it was in Japan? where fishermen caught crabs in nets. Some crabs had markings on the shell that looked like a face and these the fishermen threw back into the sea. Over time the markings began to resemble a face more and more, simply because those with a ‘face’ were thrown back, so survived to breed even more with the special markings. I find it interesting that Nature adapts like this.

    Liked by 1 person

  3. I like the crab in the last picture, looks like eyes on the back of its shell.

    Liked by 1 person

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