Wednesday, October 31, 2012

A mollusc in the shape of a heart

Rough seas can deposit very interesting creatures on the shore.  

A walk on the beach after a storm can be very rewarding especially for those who do not dive or snorkel and have to rely on the waves to see some of the creatures that live below the surface.

Many creatures are too fragile to survive the pounding waves intact but many mollusc have very strong shells and remain intact even after a considerable amount of pounding.

Cockles have strong, compact heart-shaped shells that can be rolled over the sand and banged without damage to the living mollusc. 

About twenty species are found in the Mediterranean of which ten have been recorded in Maltese waters. 

The cockle shell, known in Maltese as xedaq, is common in sandy bottoms while the slightly smaller edible cockle, known in Maltese as arzella tal-Marsa prefers brackish water such as is found in estuaries.

Cockles are bivalves, that is, molluscs whose shell is made up of two opposing valves attached together by means of a flexible ligament.   

About 9,200 species, of which 8,000 live in the sea, are known to exist. These range in size from miniscule species to the giant clam which can grow up to 200 kilograms. About 230 species have been recorded in the seas around the Maltese islands with another two species live solely in fresh water.

Some species live attached to solid surfaces while others bury themselves in sediment. Scallops one of which is known in Maltese as pellegrina are free living and can escape from predators by clapping the valves together and creating a jet of water to swim away from danger.

Most bivalves are edible although relatively few species are collected for consumption. Nowadays large numbers are farmed in many parts of the world not only for sale in food markets but also for the cultivation of pearls. 

This article was published in The Times on 14.03.2012.

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