Phylum Brachiopoda (Brachiopods)

1. Exclusively found in marine environments.
2. Body composed of two calcareous shells arranged dorsoventrally.
3. Larval stage consists of a trochophore.
4. Excretory system consists of metanephridia.
5. Usually have separate sexes.
6. Possess a lophophore that aids in feeding.
7. Distributed worldwide.

The brachiopods , commonly called lampshells, consist of two different classes: the Inarticulata and Articulata. The inarticulates are characterized by the valves being connected by muscles. Their shells are composed of calcium phosphate, and have an abundance of horny protuberances on their shell. Articulate brachiopods are characterized by their hinged valves and shells composed of calcium carbonate. Other differences in these classes are in terms of the digestive cavity, and how the organism is attached to the substrate. Inarticulate brachiopods only have a mouth, whereas the articulates have both a mouth and anus. Inarticulates have a longer peduncle and can burrow deep within the mud of the ocean floor. The articulates are usually found attached to rocks or other shells, and possess a shorter peduncle. Brachiopods possess a primitive heart with an open circulatory system. They have blood channels to supply necessary parts of the body with nutrients. The blood system is responsible for the circulation of digested food, while oxygen transport is the reponsibility of the coelomic fluid.

• Brachiopods feed by means of a lophophore. This structure is a folded crown of hollow tentacles bearing cilia. At the base of the lophophore is the mouth. When feeding takes place the valves gape so that water can flow over the lophophore. The ciliated tentacles cause the food to become trapped and get swept in towards the mouth. The journey then continues on towards the digestive tract. The lophophore actually causes a current for food to come in and for rejected materials to be carried away.
• Most brachiopods have separate sex cells, although some are hermaphroditic. The gametes are released into the water and then fertilized. In some cases the embryonic development takes place in the parent shell. The embryo develops into a pelagic ciliated trochophore that eventually drops to the bottom. The larvae then undergoes metamorphosis and the end result is a benthic adult organism.

1. Banister, Dr. Keith and Dr. Andrew Campbell. 1985. The Encyclopedia of Aquatic Life. New York: Facts on File.
2. Bertin, Leon. 1967. Larousse Encyclopedia of Animal Life. New York: The Hamlyn Publishing Group Limited.
3. Bullough, W.S. 1958. Practical Invertebrate Anatomy New York: St. Martins Press.