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| Image by Open Up! |
What are Brachiopods?
Brachiopods are actually a PHYLUM of animals. That's right a whole GROUP of animals that most folks have probably never heard of!
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| image by Herman Giethoom |
Brachiopods are a very old, old group of invertebrates with a relatively rich fossil record. They have two shells (and are superficially similar to bivalves, e.g; clams and mussels) but are better known in several other ways...
Brachiopods are one of the few groups of marine animals which live ONLY in the Ocean! (Echinoderms being one of the others...)
Some places you learn about some new mammal, but HERE at the Echinoblog? you learn about a whole PHYLUM of animals in five easy steps!
1. What does the name mean?
Brachiopoda, when you break it down: "brachio"=
arm and "poda"=
foot. Wha? The Arm foot?
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The name refers to a structure known as the
pedicle. That's the purple stalk bit that is anchoring the animal down to the substrate. This is how the pedicle looks
in the group informally known as the "articulate" brachiopods. Arm refers to the muscular arm-like aspect and "foot" to its use (or disuse) in attatching to the bottoms.
The pedicle manifests in two different ways relative to which of the two major groups of brachiopods you are looking at!
One group has been referred to as the "Articulate" brachiopods.
And yes; they are very well spoken thank you. ha ha.you have now caught up with the jokes:
The "articulate" part refers to how the two shells have teeth that articulate with one another.. Here are some hinges on various brachiopod valves.. (
images below by Open Up! fr. this awesome photoset fr. the University of Tartu-go take a look at some AWESOME photos! )
In the "inarticulate" brachiopods the pedicle is this much more developed tail-like feature. the animal is almost kind of a worm. These live in burrows. People eat these! (see below)
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| Lingula adamsi Dall by Changhua Coast Conservation Action |
2. So these look like clams? What's the diff?
Relative to the animal inside, brachiopod shells are oriented top-bottom vs. those in bivalves, which are oriented left-right
Yes. I know the symmetry seems strange and can be oddly difficult to "get" the first time around. Here are some brachiopods...
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image by mpjones_007
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Image by Alexander Semenov
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and here's some clam for comparison (positioned for convenience!)
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| Image by Royston Vasey |
3. What/How do they eat?
Brachiopods have a feathery feeding structure called a
lophophore! Brachiopods are basicaly suspension feeders. Water flows in and over the lophophore and tiny finger-like bits called cilia pick the food up!
Here's some reality from the very talented Arthur Anker showing the lophophore with the animal's valves open!
A further
GREAT pic of the lophophore can be found here..
And here is the diagrammatic approach that gives you a general idea of what you're looking at.... The animal below has been turned upside down to show parallel orientation with the pic above...
4. In the Paleozoic (roughly 250-500 million years ago), brachiopods were once THE happening invertebrate!
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| image by David Cartier |
Earliest known fossils date back to the Cambrian (600 million years ago-but probably more), but the time of the brachiopod was in the Paleozoic! (bear in mind how vast a time period 250 million years is.. that's MUCH older than humanity..). They dominated in diversity and abundance. This was their "time"... Sadly, most brachiopods underwent a huge extinction at the end of the Paleozoic...
According to the
World Brachiopod Database only about 385 species occur today from the ~30,000 described (mostly fossil) ones!!
Many of these species live in out of the way and isolated places...
Here is a gorgeous pic of
Coptothyris adamsia from the Sea of Japan
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| Image by Alexander Semenov |
Here is Laqueus californica from Monterey Bay in some pretty amazingly high densities...
and more from Alexander Semenov:
Hemithyris psittacea (Rhynchonella psittacea)
5. Geology! Fossil Brachiopod Shells are sometimes replaced by Pyrite! (aka Fool's Gold)
In the fossil record, the "shells" (called valves) of brachiopods sometimes undergo a process in which they are replaced with pyrite aka fool's gold!
This makes them golden and sparkly!
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| Image by jsj1771 |
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| Image by E. Sese |
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| Image by JS1771 |
5a! More Geology Fun! Brachiopod valves are often found in cross sections of rock!
Geologists know the value of a good cross section! Brachiopods are VERY abundant in Paleozoic rock. And if you cut through the shells of one you get some pretty distinctive impressions in the rock..
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| Image by Maitri |
Sometimes there are minerals such as agate!
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| Image by Captain Tenneal |
Brachiopod shells can be pretty dense and sometimes you see a lot of them!
Sometimes you see some neat rare stuff.. like this soft-part preservation of a lophophore!
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| Image by Dietmar Down Under |
FUN FACT! People EAT brachiopods!
I wrote about this earlier... but yes, apparently some curry and/or garlic is appropriate....
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| Image by Peter Roopnarine |
