Typical Molluscs have:
- typical protostome coelomate characters coelom reduced to a vestigial GONOCOEL (surrounding reproductive organs & a few other structures)
- a haemocoel as the primary body cavity an open circulatory system
- viscera concentrated in a VISCERAL MASS
- a thick, epidermal-cuticular layer of skin called the MANTLE which secretes the SHELL
- large, well-defined, muscular "foot"
- buccal opening with a rasplike RADULA feeding structure
- large, complex metanephridia serving as excretory system
- primitive forms have a TROCHOPHORE larva; in more derived forms, the trochophore develops into a more complex VELIGER larva before metamorphosis into the adult form
Some major classes of Molluscs
- Polyplacophora - (poly = "many"; plac = "plate"; phor = "to bear") - Chitons
- all marine, benthic
- Gastropoda - (gastr = "stomach"; pod = "foot") - Slugs & snails
- free-living; marine, freshwater or terrestrial high degree of cephalization with well-developed sense organs
- torsion
- single shell, often spiral or conical
- Bivalvia - (bi = "two";valve = "shell"; ) - Clams, oysters, mussels, etc.
- marine and freshwater gill used for both respiration and gas exchange
- all are suspension filter-feeders
- Cephalopoda - (cephalon = "head";pod = "foot"; ) - Chambered Nautilus, Squids, Octopus
- exclusively marine fast-swimming predators
- camera eye is analogous to the vertebrate eye, and forms complex, color images like our own
- comparatively intelligent; Octopus are able to solve problems!
Van Dover, along with scientists from the Swedish Museum of Natural History and the Monterrey Bay Aquarium Research Institute, discovered a new mollusk while doing research around vents on the floor of the Indian Ocean..