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What are Brachiopods?

Michael Anissimov
Michael Anissimov
Michael Anissimov
Michael Anissimov

Brachiopods, also known as lampshells or "brachs," are a group of shellfish, members of phylum Brachiopoda. Although some of them look superficially like clams, they're really completely different — both on the outside and the inside. Brachiopods are phylogenetically unique enough to merit their own phylum, whereas clams are bivalves, part of phylum Mollusca. Brachiopods are called articulate or inarticulate based on whether their two shells have a hinge (articulate) or are held together based on muscles alone (inarticulate).

Brachiopods are stationary filter feeders that feed by means of a frilled appendage called a lophophore. Unlike bivalves, which have two symmetrical shells on either side, brachiopods have shells symmetrical about a central axis but not with respect to one another. Part of this has to do with the brachiopods' other appendage — the pedicle. The pedicle is a fleshy stalk that the brachiopod uses to affix itself to a surface, usually permanently. One shell has a special opening for the pedicle to protrude, hence it is called the pedicle valve. The pedicle valve is the top shell of the animal, and it is often thicker and harder than the lower valve (the brachial valve), to protect against attacks from above.

Woman holding a book
Woman holding a book

Though rare today, brachiopods are very important in the context of evolution, for several reasons. Brachiopods were the first bilaterian animals to enclose themselves in a hard shell and adopt a stationary lifestyle. Brachiopods dominated the ocean bottoms for the entire Paleozoic era (from 542 to 251 million years ago), far outnumbering the bivalves that cover the ocean floor today. Because of their abundance and hard shell, brachiopods are also the most common fossil. They were especially successful from the Ordovician period onwards, when many filter feeders evolved and began to exploit the abundant food particles building up in the Earth's oceans.

During the Permian-Triassic extinction 251 million years ago, brachiopods all but went extinct. 96% of brachiopod species died off. Since then, brachiopods have been outcompeted by bivalves, which use siphons instead of a lophophore to feed, and are often mobile, crawling along the sea floor or burrowing into the substrate using a muscular foot.

Frequently Asked Questions

What are brachiopods and how do they differ from bivalves?

Brachiopods are marine animals with two shells, similar to bivalves, but they differ anatomically. Brachiopods have shells on their top and bottom, unlike bivalves which have shells on the left and right sides. Additionally, brachiopods possess a unique feature called a lophophore, a feeding structure, which bivalves lack. According to the Paleontological Research Institution, there are about 12,000 extinct species of brachiopods and only about 400 living species today.

Where can brachiopods be found in the world?

Brachiopods are found globally, predominantly in marine environments from the intertidal zone to depths of over 6,000 meters. They prefer colder waters and are often located in areas with stable environmental conditions. The majority of living brachiopods are found in the Southern Hemisphere, as reported by the World Register of Marine Species.

How long have brachiopods been in existence?

Brachiopods are among the oldest known fossils, with an existence that dates back to the early Cambrian period, over 500 million years ago. They reached their peak diversity during the Paleozoic era, particularly in the Ordovician and Silurian periods, as per fossil records. Their long evolutionary history showcases their resilience and adaptability.

What do brachiopods eat and how do they obtain their food?

Brachiopods are filter feeders; they consume microscopic organisms such as algae and detritus suspended in the water. They use their lophophore, a crown of tentacles lined with cilia, to create water currents that draw food particles towards their mouth. This efficient feeding mechanism allows them to thrive in nutrient-rich marine environments.

How do brachiopods reproduce?

Brachiopods primarily reproduce sexually by releasing eggs and sperm into the water column, where external fertilization occurs. Some species are hermaphroditic, possessing both male and female reproductive organs. According to research, larval brachiopods may spend several weeks as plankton before settling on the seafloor and metamorphosing into their adult form.

Are brachiopods considered important to science or ecology?

Brachiopods are significant to science, particularly in paleontology, as their extensive fossil record provides insights into Earth's history and past marine environments. Ecologically, they contribute to biodiversity and can be indicators of environmental change due to their sensitivity to water quality. Their role in marine ecosystems, although not as prominent as some other organisms, adds to the complexity and balance of these environments.

Michael Anissimov
Michael Anissimov

Michael is a longtime AllThingsNature contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Learn more...
Michael Anissimov
Michael Anissimov

Michael is a longtime AllThingsNature contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

Learn more...

Discussion Comments

anon178007

is there any thing that says about their feeding? it's hard to read it that small.

anon139692

any drawings of them? i am having a hard time visualising them.

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