Anatomy of finfish and shellfish

Unit 13 - Mollusca

13.3.3. Respiratory System

There are two elonged gills in the mantle cavity, one on either lateral side of the visceral mass to which their proximal ends are attached. By alternate expansion and contraction of the mantle, the respiratory water passes into and out of the mantle cavity through the wide circular opening between the neck and collar. It flows over the gills, supplying oxygen to the blood and carrying away carbon doixide.