RESPIRATORY FLOW IN MUSTELUS

Abstract

Trained unanesthetized dogfish (Scyllium canicula and Scyllium catulus) were fitted into a two-compartment tank which separated the inspiratory water from the expired water. The water levels could be varied separately and water from both compartments was sampled and analyzed. The flow of respiratory water in the dogfish was about half a l./min./kg. A nearly linear relation was observed between the quantity of water pumped and the hydrostatic pressure at the front of the head if the pressure outside the gill slits be taken as zero. No respiratory mechanisms were observed which would tend to compensate for an excess or deficit of respiratory water resulting from such pressure changes. When the respiratory deficit became too great, the fish attempted to swim away. The respiratory frequency at constant temp. is independent of the respiratory flow, and may be slowed by excitement or anesthetic. Reduction of O2 tension or marked reduction of pH in the inspired water produced a swimming reaction. The respiration of elasmobranch fish is compared with that of man in a short teleological discussion.