Abstract
This paper describes the anatomic properties of a paired hollow glandular organ in the genito-urinary apparatus of Raja, and gives the chief characteristics of its secretion. The following summarizes data from Raja erinacea and Raja ocellata. 1. 1. The fluid is water-clear and free of high molecular weight protein or polysaccharide. The gland contains highly active secretory epithelium. 2. 2. The pH is 9·2 and total CO 2 is 210 mM/l. Of this, almost 40% is CO 3 2−. There is a high concentration of carbonic anhydrase in the gland. 3. 3. The Cl − concentration is about that of plasma. 4. 4. The Na + and K + concentrations are about twice those of plasma. 5. 5. The fluid is iso-osmotic with plasma, but has about one-third the urea concentration of plasma. 6. 6. The secretory is about 16 mV negative to the nutrient surface. Short-circuit current is 62 μA/cm 2. 7. 7. A net flux inward (nutrient to secretory) can be demonstrated for OH − and Cl −. 8. 8. The electrical and chemical data are consistent with an anion pump for OH − and Cl − (and perhaps SO 4 2−, with passive distribution of Na + and K +. In a third species, R. stabuliforis, the quanlitative characteristics of the fluid are the same. However, pH is lower (8·7) and total CO 2 is less (102 mM/l) with a much lower proportion of CO 3 2−. Cl − concentration and net flux are considerable greater. This species does not have carbonic anhydrase in the gland.
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