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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