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Brachipoda.pdf
- 2. Phylum: Brachiopoda Classes:Articulata Inarticulata Orders: 7 Articulate 4 Inarticulate
- 3. Brachiopod Brachiopods (brachio=arm; pod = foot) Valves are opened and closed by contracting muscles called adductor and diductor muscles.
- 4. Mode of Life Sessile and marine Attached to seafloor by pedicle at posterior Inarticulate brachiopod live in tube Adult brachiopods are filter feeders Filter food particles from water Food passes from mouth to the esophagus to stomach Animals feeding on brachiopods include starfish, crustaceans, gastropods, and fish.
- 5. They have 2 VALVES (shells) that totally enclose the soft parts. The average size is 20 - 70 mm but can range up to 370 mm. The valves can open and are hinged at one end; muscles open and close the shell.
- 6. Modified from Clarkson (1986) clam
- 7. Valves usually allow water into the shell, as they are filter feeders extracting food from seawater. The two valves are different in size (as opposed to bivalves). However; they do show a line of lateral symmetry along the middle of the organism.
- 8. The smaller valve is the BRACHIAL valve (upper in life position). The larger valve is the PEDICLE valve (lower in life position). The animal secretes the valves as it grows, the original small shell is called the UMBO and the shell grows outwards from either side of this point.
- 9. The pedicle valve has a small circular opening (FORAMEN) at the end through which a type of foot extends called the PEDICLE. The pedicle allows the brachiopod to attach itself to the sea floor. Inside the shell the body fills much of the body cavity.
- 10. Some shells like rhynchonellids have a wrinkly COMMISURE with FOLDS (one on either side of the sulcus) and a SULCUS (in the middle). Folds have inhalent and sulcus has the exhalent. The currents are therefore separated. The crenulated commissure also provides a greater surface area.
- 11. The inside of the shell is the MANTLE CAVITY and is mainly the LOPHOPHORE, which is a food gathering and water-filtering device. The important muscles are: At the posterior end is the pedicle “foot” type of ligament/muscle which when extended could usually reach outside of the shell. The main muscles were the ADDUCTOR and DIDUCTOR muscles, which were used to close the shell.
- 12. Both sets of muscles were attached to the shell and although not preserved in the fossils there are scars left from where the muscles were attached to the shell. The CARDINAL PROCESS and HINGE acts as a base on which the muscles can pull. The diductor muscles contract and pull down the cardinal process and open the shell.
- 13. As the diductor muscles relax the adductor muscles contract and close the shell. Role of the lophophore is to act as a feeding device, which collects suspended particles. Some brachiopods like spiriferids have a spiral calcite support called a lophophore support or spiralia.
- 14. On the diagram you can see that the brachiopod has TEETH (pedicle valve) and SOCKETS (brachial valve).
- 15. Brachiopods are a long-lived Phylum ranging from the Cambrian to Present. They were very common in the Palaeozoic and slightly less so in the Mesozoic but still remain important. In the present not many forms are left with approximately 70 Genera. Over 2500 fossil Genera are known. The largest were found in the Cambrian (370 mm).
- 16. Brachiopods are exclusively marine Live in environments ranging from subtidal to the abyssal Brachiopods swim only during larval stage Widespread distribution reflects free-swimming larval stage Brachiopods occur throughout the world in both cool and temperate waters Most brachiopods found in the neritic zone (waters over the continental shelf), a few are found depths of 5000 m Most brachiopods range between 20 and 70 mm, some are up to 370 mm.