Anatomy of finfish and shellfish

Unit 12 - Arthropoda

12.1.5. Respiratory System
In shrimps, as in all other decapod crustaceans, the gills lie within two branchial chambers, each of which results from a deep lateral fold of the carapace. The beating of a leaf-like flap, the gill bailer, or scaphognathite, causes water to enter the branchial chamber from below and behind that is, through opening between the thoracic legs and in front of the abdomen. The water leaves the -branchial chamber through 'a channel, directed toward the head, in which lies the beating gill bailer. As the water circulates through the branchial chamber, an exchange of gases takes place between the water and the blood in the gill filaments. At the same time there is a discharge of excess salts from the blood into the water and an uptake of needed salts from the water into the blood.