Invertebrates - Molluscs Flashcards
What is the general body plan of molluscs?
Coelomates
Bilateral Symmetry
Protostomes
Protosotomes
These are animals in which the mouth develops from a primary embryonic opening, like annelids, molluscs or arthropods.
How does the mollusc coelom differ?
Exists as appendages around the pericardial chamber, nephridia and sometimes perivisceral chamber.
What are the three distinct regions of molluscs?
Head, Foot and Visceral mass with a Hoemel coelom.
What sensory structures do molluscs have?
Eyes, Statocysts and tentacles.
What is the mollusc body vover?
A mantle that is covered in a calcareous skeleton embedded in the body wall.
What is housed in the mantle cavity?
Gills, Ctenidia, gut, nephridia, reproductive opening and osphradia.
Where does circulation occur in aquatic molluscs?
Mantle cavity.
What regional specializations does the foot have?
A radal and pericardial cavity open circulatory system.
How is mollusc excretion facilitated?
A pair of nephridial kidneys
What is the structure of the mollusc nervous system?
Cerebral ganglia, nerve ring, two nerve cords and paired ganglia.
What is the developmenet of molluscs?
Internal or External with protostome and spiral cleavage with distinct larval stages.
What are hte three primary mollusc classes?
Bivalvia
Gastropoda
Cephalopoda
What are Bivalvia defined by?
Containing of two seperate shells called valves.
Where do bivalves inhabit?
Marine and Freshwater habitats.
What are some general features of bivalves?
Expanded gills for filter feeding and respiration, dioecious with external fertilization and free-swimming larva, mostly sedentary or burrowing with bilateral symmetry.
What defines Gastropoda?
Terrestial or Aquatic, well developed head for finding food, asymmetrical body due to torsion