THE  MOLLUSCA

Class GASTROPODA

• 35,000 species of snails and slugs [Fig. 21.8, 21.9]
• marine, freshwater and terrestrial; mainly herbivores and carnivores
• coiled shell (may be lost)
• torsion [Fig. 21.7]: note position of gill and mantle cavity and anus in the figure from BIODIDAC
• gills in aquatic species; vascularized mantle in terrestrial forms
• more about gastropods from the University of Michigan

Class BIVALVIA

• 30,000 species of clams, oysters, scallops, mussels
• paired, hinged shells [Fig. 21.10]
• mainly filter feeders [Fig. 21.12, 21.13]: gills & siphons
• sedentary, infaunal and epifaunal, scallops semi-nektonic
• more about bivalves from the University of Michigan

1. Nautiloidea
1. pearly nautiluses [Fig. 21.17a]
   • external chambered shell
   • photograph from BIODIDAC

2. Coloidea
   2. squids [Fig. 21.18], cuttlefish [Fig. 21.17b], and relatives
      • giant squid: Architeuthis dux--the world's largest invertebrate

 

3. octopuses [Fig. 21.1]

Class Polyplacophora

• chitons
• 8 plates [Fig. 21.21]
• dorsal and ventral imagesof a chiton from BIODIDAC
• more about chitons from the
  • University of Michigan
  • University of Paisley

Class Scaphopoda

• tusk shells [Fig. 21.22]
• image to right showing major features of a feeding scaphopod  from BIODIDAC
• more about scaphopods from the 
  • University of Michigan
  • Museum of Paleontology

Class Monoplacophora

• [Fig. 21.23]
• dorsal and ventral imagesof Neopilina from BIODIDAC
• more about these primitive mollusks from the University of Michigan

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