He explained the increased oxygen consumption on the basis of higher 

 motor activity in other salinities where they attempted to escape 

 the salinity stress. Lofts (1956) and Rao (1958) attempted to cor- 

 relate the oxygen consumption in prawns from marine and brackish 

 water habitats with their osmotic gradients in their respective sa- 

 linity media. Lofts found that when tested in a fresh water to 

 65°/ooS range the marine population of Palaemonetes varians con- 

 sumed the lowest amount of oxygen in 26°/ooS which was close to 

 their natural habitat. The brackish water population had the lowest 

 respiratory rates in 6°/ooS. In the Indian prawn Metapenaeus mono- 

 ceros, Rao (1958) observed a similar respiratory pattern between the 

 marine and brackish water populations. From a more recent study 

 Kutty et al. (1971) reported that the prawn Penaeus indicus accli- 

 mated and tested in a 5 to 60°/ooS range exhibited the lowest oxygen 

 uptake in 10-15°/ooS. These findings suggest that the energy spent 

 for osmotic regulation can be measured from the amount of oxygen 

 consumed. Also the results imply that the higher the osmotic gra- 

 dient between the blood salt concentration and the external salin- 

 ities, the more energy prawns would require for regulation. The 

 results of the present study showed a good correlation at 25 °C 

 between the metabolic and osmotic responses, thereby tending to 

 confirm the findings of the above authors. 



When the test temperatures were altered from normal to 

 18° or 32°C the above correlation did not exist any more. Under the 

 changed temperature conditions the osmotic and chloride regulation 

 pattern remained intact as in 25 °C with a few quantitative changes; 

 but the salinity- related respiratory pattern was altered from the 

 original. At 32 °C the oxygen consumption was higher in IS^/ooS than 

 in other media. In 2 and 5°/ooS the consumption was lowest. The 

 respiratory rates no longer showed any relation to the osmotic gra- 

 dient in the respective salinities. 



