Bivalvia Flashcards
What are the characteristics of Bivalvia?
- Laterally compressed body
- Bivalve shell with a dorsal hinge
- Spacious lateral mantle cavities
- Minimal cephalization
- NO radula
How is water circulated?
External water circulated thru the mantle cavity
-in the inhalant siphon and out the exhalant siphon
How is the foot modified in Bivalvia?
Flattened, modified for burrowing
What holds the shell valves together?
What open/close the shell valves?
Hinge ligament
Close: Anterior/Posterior adductor muscles
Open: hinge ligament (also re-extends muscles)
How does the hinge ligament open the shell valves?
It is deformed by the muscles contracting. When that energy is released, it springs back to its original shape
How do Bivalves burrow?
a)
1. Shell adductor muscles relax, shells gape open to anchor shell
2. Foot laterally compressed, pushes into substrate
b)
3. Expansion of foot terminus (anchor)
4. Contraction of adductor muscles (closes shell)
5. Contraction of shell-attached dorso-ventral muscles pulls clam down
Where are the shell-attached dorso-ventral muscles found?
In the foot
What are the inner, middle and outer lobes in bivalves specialized for?
Inner: muscle
Middle: sensory (photoreceptors)
Outer: shell secretion
What is the shell covered by?
A layer of proteinaceous periostracum
What is the shell secreted by?
The mantle
Where are sensory structures found? What are some examples?
at the mantle margin
eg: tentacles, eyespots
Identify the features of an empty shell
- pallial line
- pallial sinus
- anterior/posterior adductor muscle scars
- teeth (at hinge)
- hinge ligament
What are the 2 subgroups?
Protobranchia
Autobranchia
How is autobranchia subdivided?
Pteriomorpha (mussels, oysters)
Heteroconchia (most extant bivalves)
How do PROTOBRANCHIA feed?
-deposit feeding using palp tentacles