How is the respiratory system in aquatic molluscs characterized? What adaptive respiratory structure do terrestrial molluscs present?

How is the respiratory system in aquatic molluscs characterized? What

1.	How is the respiratory system in aquatic molluscs characterized? What adaptive respiratory structure do terrestrial molluscs present?
Answer» Aquatic molluscs oxygenate their blood through gills in direct contact with water. In terrestrial molluscs the rich vascularity under the mantle cavity absorbs air doing the role of a primitive lung.