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#15 Skeletons of sea creatures

Vani went to Goa for a holiday with her family. She was very happy to see hundreds of seashells at the beach. She enjoyed collecting the seashells but wondered how those seashells were formed.

Did you know that seashells are actually skeletons of many sea creatures? Just like we have our skeletons inside our body, seashells are the skeletons of some marine (animals that live in seawater) animals called Molluscs outside their soft bodies. Molluscs are soft bodied but hard shelled creatures like oysters, clams, squids, octopus and snails. The shells are a part of them and they are attached to the shells by their muscles.

The shells are composed of a form of limestone; this limestone is built by the mollusc itself. The mollusc has certain glands in its body, which help it to take the limestone from water and deposit it in the particles along the inside of the shell. As a mollusc grows in size, the shell too increases in size and thickness. The shell has three layers making it strong. It has a tough outer layer, a chalky kind of middle layer and an innermost shiny layer. The shells protect the animals from storms, predators and strong currents.

Just as land animals leave their skeletons behind when they die, the mollusk too leaves its shell behind when it dies. The abandoned shell is sometimes used by other sea creatures like the hermit crab. As the hermit crab grows, it looks for bigger shells.

All shelled molluscs do not live in the sea, some live on land and some in freshwater.There are more than fifty thousand varieties of mollusc shells. Today, due to all the pollution, there is an excess of carbon dioxide in the sea and ocean waters, due to which the water has become more acidic in nature, so these animals make thicker shells to protect themselves from acidic water.

different kinds of mollusc shells



















Seashells were once used as weapons and tools and the larger shells like those of the giant clams have been used as bowls for eating! Seashells were even used as a currency!

Some sea shells are very pretty in colour, however, the colour that a sea shell has is not just to make it look pretty but to help the mollusc to camouflage itself for protection from its predators. Do you know how the mollusc gets these colors?

Explore Response
#15 Answer

TEAM EXPLORE:  Most molluscs have pigment glands which contain colouring matter, which helps them produce the colour for their shells.

Best Response
Mrs. Anuradha Chethak 9 years.
June 19, 2014
Some shells contain pigments which are incorporated into the structure. This is what accounts for the striking colors and patterns that can be seen...

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Answers (1)
Mrs. Anuradha Chethak, 9 years | Posted June 19, 2014
Some shells contain pigments which are incorporated into the structure. This is what accounts for the striking colors and patterns that can be seen in some species of seashells, and the shells of some tropical land snails. These shell pigments sometimes include compounds such as pyrroles and porphyrins.

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