Ammonia excretion in Octopus dofleini

Abstract

1. 1. Simultaneous measurements have been made of the ammonia content and pH of the blood, pericardial fluid and kidney sac urine of Octopus dofleini. 2. 2. Although the concentration of total ammonia (ammonia molecules+ ammonium ions) is much greater in the acid urine than in the neural blood the concentration of molecular ammonia is always higher in the blood. It is concluded that ammonia enters the urine by diffusion as ammonia molecules and is trapped as the ammonium ion. 3. 3. The pericardial fluid is slightly alkaline and contains a lower concentration of total ammonia than the blood. Significant synthesis of ammonia occurs within the kidney. 4. 4. The renal appendages have a considerable glutaminase activity and there is a net loss of glutamine and amino acids from the blood on passage through the kidney. The total concentration of ammonia in the blood usually increases on passage through the kidney. 5. 5. Measurements of the ammonia concentration of the blood show that significant loss of ammonia takes place from the ctenidia.