Invertebrate
Zoology Mollusca
Molluscs
range in size and body form from the giant squid, measuring 18 meters in length,
to the smallest garden slug, less than one centimeter long. In spite of this diversity, the phylum Mollusca
is not difficult to characterize.
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Phylum Mollusca
1.
Body of two parts: head-foot and visceral
mass
2.
Mantle that secretes a calcareous
shell and covers the visceral mass
3.
Mantle cavity functions in excretion,
gas exchange, elimination of digestive wastes, and release of reproductive
products
4.
Bilateral symmetry
5.
Protostome characteristics, including
trocophore larvae, spiral cleavage, and
schizocoelous coelom
formation
6.
Coelom reduced to cavities surrounding
the heart, nephridia, and gonads
7.
Open circulatory system in all but
one class (Cephalopoda)
8.
Radula usually present and
used in scraping food |