THE PHYSIOLOGICAL RESPONSE OF THE ESTUARINE CLAM, RANGIA CUNEATA (GRAY), TO SALINITY. II. UPTAKE OF GLYCINE

¹ Department of Biology, Texas A&M University, College Station, Texas 77843

1. The effect of salinity on the uptake of dissolved C¹⁴-labeled glycine by Rangia cuneata and isolated gill tissue was studied.

2. The percentage water in Rangia tissue ranged from 81% at 1 S to 73% at 32 S, while the ash-free dry weights at these same salinities were 2.5% and 7.6%, respectively. The per cent water and per cent ash values were linear throughout this salinity range.

3. The uptake of glycine was relatively uniform at salinities between 6 and 32 for whole animals and between 10 and 25 for gill tissue.

4. At salinities below 6 uptake decreased sharply and in a linear fashion to a low at 1 S. Suppression of uptake was also exhibited when gill tissue was exposed for 90 minutes at 32 S.

5. With increasing salinity the percentage utilization of accumulated glycine increased, but the rate of glycine incorporation into the alcohol insoluble fraction decreased.

6. Removal of glycine by gill tissue from salinities of 10 to 25 occurred at a relatively linear rate up to 90 minutes and the levels obtained were considerably higher than those for whole animals when compared on a basis of cpm per mg ashfree dry weight.

7. In a constantly flowing system Rangia at 15 S removed 0.16 µ moles of glycine/g/hour for a period of 11 hours, when supplied with 5.2 µ moles of glycine per liter.

8. The significance of the relationship between salinity and glycine uptake, and possible explanations for this relationship are discussed.