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Clam

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== Reproduction ==
== Reproduction ==
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Clams reproduce sexually and like most mollusks they are hermaphroditic although some soft shelled clams are dioecious, meaning they have distinct genders [http://www.seacoastonline.com/articles/20090603-LIFE-906030327]. Clams mate in the spring when the water temperature begins to rise. The clams realease both their sperm and their eggs into the water to be fertilized. Once a free swimming sperm fertilizes the egg the cells within the egg divide until they form a free swimming larval called a trochophore (Porch, p469).
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Clams reproduce sexually and like most mollusks they are hermaphroditic although some soft shelled clams are dioecious, meaning they have distinct genders [http://www.seacoastonline.com/articles/20090603-LIFE-906030327]. Clams mate in the spring when the water temperature begins to rise. The clams realease both their sperm and their eggs into the water to be fertilized. Once a free swimming sperm fertilizes the egg the cells within the egg divide until they form a free swimming, larval called a trochophore (Porch, p469). The trochophore shows no resembleance to its parents for they lack a shell and are more round than flat. The trochophore matures into a veliger, which is the second stage of its development. The veliger begins to resemble its parents with the begining stages of a shell. The veliger has a unique way of feeding.  A fromation of cilia srurrounding the mouth called a velum assist the veliger capture food particles. The velum is also used to push the veliger trhough the water (Russel, p5).
== Ecology ==
== Ecology ==

Revision as of 00:58, 22 November 2009

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Clam
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Scientific Classification
Selected Clams
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Contents

Introduction

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Anatomy

Description

The clam is a flat, round invertebrate that posses a shell which consists of two separate valves. The two valves are held together by a hinge and the shell is kept closed by a tense abductor muscle. [1] Each valves is created by secretions from the mantle and each valve consist of three layers (Porch, p468). The first, outermost layer is meant for protection and it has a rough, bumpy texture. The middle layer is a hard, protective layer made of calcium carbonate. Lastly, the third innermost layer is made of a smooth, pearly substance. Because it is a mollusk, the clam has a foot which it uses to burrow in the sand. The clam has two tube-like siphons that it uses to filter water. Water is brought into its body through the incurrent siphon and the water is removed from its body through the excurrent siphon. The clam breathes using it's gills. Water containing oxygen is brought into the gills and the many blood vessels within the thin-walled gills exchange carbon dioxide. The gills also assist in obtaining food. The incurrent siphon brings water into the gills and mucus secreted by the gills and the palps, which are organs surrounding the clams mouth, capture tiny bits of food [2]. The food is then moved by cilia on the palps through the esophagus and into the stomach. The food particles are later digested by the digestive gland attached to the stomach. The intestines take care of indigestible materials and expel them trough the anus. A clam has an open circulatory system with a pumping heart that send its clear blood through the blood vessels to distribute food an oxygen. A clam also has one kidney to filter the waste from its blood. Within the clam’s nervous system are three ganglia which are connected by nerves and sensory organs including light and touch receptors on the mantles edge.

Reproduction

Clams reproduce sexually and like most mollusks they are hermaphroditic although some soft shelled clams are dioecious, meaning they have distinct genders [3]. Clams mate in the spring when the water temperature begins to rise. The clams realease both their sperm and their eggs into the water to be fertilized. Once a free swimming sperm fertilizes the egg the cells within the egg divide until they form a free swimming, larval called a trochophore (Porch, p469). The trochophore shows no resembleance to its parents for they lack a shell and are more round than flat. The trochophore matures into a veliger, which is the second stage of its development. The veliger begins to resemble its parents with the begining stages of a shell. The veliger has a unique way of feeding. A fromation of cilia srurrounding the mouth called a velum assist the veliger capture food particles. The velum is also used to push the veliger trhough the water (Russel, p5).

Ecology

Description




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