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.
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.
