The effect of salinity variations on the metabolic rates of 

 marine and brackish water invertebrates have been grouped by Kinne 

 (1971) under four headings: 



1. Increase in subnormal salinities and/or decrease in supra- 

 normal salinities; 



2. Increase in subnormal and supranormal salinities; 



3. Decrease in subnormal and supranormal salinities; 



4. Remain essentially unaffected. 



Types 1 and 2 represent, according to Kinne, largely the meta- 

 bolic rates in euryhaline invertebrates; type 3 represents the stenohaline 

 forms; and type 4, the holeuryhaline (or extremely euryhaline) forms. In 

 classifying these types Kinne evidently did not consider the tempera- 

 ture effect. When both temperature and salinity factors are involved 

 simultaneously, types 1, 2, and 3 metabolic responses are observed in 

 the same species of brown shrimp. 



Metabolic Compensation to Temperature Change 



At 32°C the respiratory rates did not increase above the levels 

 in 25°C in 2, 5, and 36°/ooS. On the contrary, in 15°/ooS the 

 oxygen uptake increased in proportion to the temperature rise from 

 18°C. The temperature effect on respiration was consistent between 

 18° and 25°C in all test salinities; but the test temperature effect 

 of 32°C disappeared progressively as the test salinities were in- 

 creased or decreased from 15°/ooS. Consequently, variations in the 

 respiratory rates became nonsignificant between 25° and 32°C in 2, 

 5, and 36°/ooS. This might reflect a possible failure to increase 

 the oxygen consumption at 32°C beyond the levels in 25°C. Since the 

 failure occurred at 32°C, naturally one might suspect the likelihood 

 of a starvation effect. Earlier in the results, the decline in res- 

 piratory rates at 25° and 32°C in 10, 15, and 25°/ooS were attributed 

 to a possible starvation effect; but no such effect was seen in 2, 5, 

 or 36°/ooS. It appeared as though in extreme salinities the shrimp did 



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