Micropuncture Studies of Chloride Concentration and Osmotic Pressure in the Crayfish Antennal Gland.

The gross microscopical anatomy of the crayfish antennal gland has been well and repeatedly characterized (Marchal, 1892; Peters, 1925; Maluf, 1939). Examination of the anatomy of the organ has yielded little information elucidating its basic functional mechanism. Since the work of Schlieper & Herrmann (1930) it has been known that the crayfish excretes a urine that is markedly hypotonic to the blood. However, the mechanism by which the animal does this is still obscure. Two conflicting theories have been advanced to explain the functional mechanism of the crayfish antennal gland. Peters (1935) concluded that the primary urine is formed by filtration of blood into the most proximal portion (coelomosac) of the antennal gland, the nitrate being modified more distally in that organ. (The evidence for Peters's conclusion will be reviewed in more detail in the Discussion.) Maluf (1939,1941 a-c) made rather extensive studies of the anatomy and physiology of the crayfish antennal gland. From these studies he concluded that the antennal gland is a secretory kidney, secreting all normal urine components plus the renal test substance inulin. Riegel & Kirschner (i960) re-examined the excretion of inulin and studied the excretion of glucose by'the crayfish. They also critically examined Maluf's evidence for secretion of inulin (and xylose). From their work, Riegel & Kirschner concluded that there is little evidence that the crayfish antennal gland forms primary urine by secretion. At the same time, they pointed out that there was little evidence to support the view that filtration under hydrostatic (arterial) pressure was responsible for primary urine formation, although it seemed likely that ' filtration 'J of some kind was involved. Riegel (1961) has shown that hydration and low temperature have effects on excretion in crayfishes similar to their effects on excretion in animals that have filtration-reabsorption kidneys. In the present work, freezing-point depression ( = osmotic pressure) and chloride