Thursday, 22 November 2012

EXTERNAL AND INTERNAL FEATURES OF A CLAM


 We have observed external and internal features of clams. We have identified the dorsal and ventral sides of the shell. On the ventral side there is a small bump which is the oldest part of the shell, it is called the umbo. There is also a hinge ligament which joins the two valves together. The hinge ligament allows the valves to open and close. It is softer than the shell so it doesn't crack. We also saw the growth rings on the shell that indicates its age.
The first thing we saw when we opened the shell were the adductor muscles. These are used to open and close the valves. If we pull them off, muscle scars are left on the shell. You can often see the adductor muscle scars on the shells when you eat molluscs! We also located the muscular foot used to move and to bury itself into the sand. We saw the mantle, a fine membrane that covers the mollusc and the gills used to breathe. The gills are easy to recognise because of the folds they have to increase the respiratory surface. We also located the incurrent and excurrent siphon. If you look carefully at the photograph you can see the parts.

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