Characters and Anatomy

Morphology of the teeth and gills

Tooth Patterns

The teeth located along the edge of the valves interlock when the valves are clasped together, so ensuring that they close efficiently with no displacement. Bivalves display eight patterns of the teeth:

TOOTH TYPE	DESCRIPTION
DESMODONT	Teeth are reduced or absent all together
DYSODONT	Small simple teeth located near the edge of the valve
TAXODONT	Numerous teeth arranged in a radial pattern fanning out upwards
ACTINODONT	Numerous teeth arranged in a radial pattern fanning out downwards
ISODONT	Large teeth found either side of the internal ligament pit
SCHIZODONT	Large teeth, sometimes grooved
PACHYODONT	Very large blunt teeth
HETERODONT	Cardinal and lateral teeth

Gill Structures

There are four known gill structures seen in bivalves. Gills are important as they assist in the filtering out of food particles an oxygen out of water brought into the bivalve via the inhalant siphon.

GILL TYPE	DESCRIPTION
PROTOBRANCH	This gill structure tends to occur in primitive groups, and appears as a small leaf-like structure
FILIBRANCH	This gill structure consists of individual filaments forming 'W'-shaped structures that come together to form lamellar sheets.
EULAMELLIBRANCH	These form 'W'-shaped gills with cross-partitions joining the filaments to create water-filled cavities in between them.
SEPTIBRANCH	These gills are only found in Poromyacea a super-family of the rock borers. They run transversely across the mantle cavity, enclosing the inner chamber, with only a small connection to the outer cavity

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