Clams are marine creatures that burrow into the sediment of the ocean floor. They are bi-valves that can live in both fresh water and salt water. Bi-valve refers to the two shells that form the outer shell of the clam that is hinged together with a joint and ligament. Clams are not only tasty, but also fascinating creatures that produce their shells out of the minerals in the water that surrounds them.
A Look at Shells
Shells are the houses and means of protection of many water-dwelling creatures including mollusks, chitons and clams. Many shells are designed for specific purposes, such as burrowing, anchoring and growing camouflage plants. Shells come in many interesting shapes and sizes, as one walk on the beach will show. They also tell much about the life of the animals contained within it. A shell can indicate predator attacks and subsequent healing of the wounds of battle. According to the Conchologists of America, shelled creatures live in rocky outcrops, among seaweed, on coral and buried under seabeds.
Anatomy of a Clam
Clams possess an outer shell that consists of two, equal-sized parts connected by four interlocking teeth that create a hinge. The clam attaches to these shells by means of an outer organ called a mantle. Clams also have a very basic cardiovascular structure that consists of a small heart, two arteries and two veins. According to Reefs, their gills do the work of gas exchange, filtering of food particles and removal of toxic substances. Their nervous system provides responses for survival, and they possess a simple digestive system that breaks down food and eliminates waste. Clams are hermaphroditic, that is, they possess the sexual organs of both male and female.
How Clams Produce Shells
Clams create their shells from the calcium that is present in the water around them. It is the mantle that holds clams in their shell that actually produces the shell. The clam extracts the several types of calcium deposits available in the water and stores it for weeks or even months. Then it releases the material in a kind of loose glue, adding bits to the rim of the shell as the clam grows. This material must harden into the same consistency as the rest of the shell. The ridges on the shell tell how old the clam is.
Pollution & Shell-building
Clams are sensitive to the effects of pollution because they filter the water around them. They must extract the minerals within the water to produce their protective shell covering. Disturbances in the carbon dioxide levels in the atmosphere affect the amount of calcium carbonate they need for shell building, according to GlobalChange.
- clam image by bedecs from Fotolia.com