rinE (Oivs) 



Figure 32. — Temperature and swimming activity of post- 

 larval brown shrimp. 



Opecoeloides fimbriatus , in shrimp varies 

 widely from bay to bay. Further work of this 

 type is necessary to determine whether shrimp 

 are "tagged" with natural parasites. Such 

 information may provide biological methods 

 useful for tracing movements of shrimp from 

 their estuarine nursery areas to the fishery 

 offshore. 



David V. Aldrich, Project Leader 



METABOLISM OF ESTUARINE 

 ORGANISMS 



Like the other projects in this program, 

 the metabolism project is concerned with how 

 physical factors affect the behavior of shrimp. 

 We, therefore, deal with effects that are not 

 readily visible within the organisms. We now 

 are investigating how salinity and temperature 

 affect the oxygen requirements of postlarval 

 shrimp. 



The amount of oxygen that an animal re- 

 quires varies with the temperature, the amount 

 of food it eats, the work it must do to maintain 

 itself in its environment, and its size. A 

 smaller animal, for example, uses more 

 oxygen per unit of body weight than does a 

 larger one. We are extending the study begun 

 on larger animals to postlarval shrimp of 

 various sizes to find the amount of oxygen 

 they require. Only brown shrimp from 12 to 

 25 mm. long have been tested in the Warburg 

 apparatus (fig. 33). Although the containers 

 have a 15 -ml. capacity, only 3 ml. of fluid are 

 used. Even in such small volumes, individual 

 postlarvae have survived for 48 hours in water 

 of salinity of 25 p.p.t. at 25° C. Oxygen con- 

 sumption decreases, however, when animals 

 are tested on a second day. 



To compare our present results with those 

 obtained earlier from large shrimp, we are 



Figure 33. — Technician preparing Warburg apparatus. 



determining wet and dry weights. Determina- 

 tions from 20 postlarvae gave body-water 

 percentages of 70 to 80 percent (mean, 76.5 

 percent). 



We have chosen 25° C. and about 25 p.p.t. 

 salinity as standard conditions under which to 

 measure oxygen uptake since both white and 

 brown shrimp grow well in this combination. 

 The smallest amimals (12 mm.) use more than 

 twice as much oxygen per xinit weight as the 

 25 -mm. animals. The temperature also affects 

 the oxygen requirement. Aninnals at 25° C. use 

 twice as much oxygen as animals at 15°C. re- 

 gardless of size. 



The amount of oxygen used may be affected 

 also by changes in the salinity. We have shown 

 previously that postlarval brown shrimp caji 

 grow at a salinity of 2 p.p.t. if they are 

 acclimated for 60 to 72 hours. Similarly, they 

 survive this salinity for 24 hours if they are 

 acclimated for 12 hours. Both of two post- 

 larvae placed directly in 2-p.p.t. water from 

 23 p.p.t. died, however, within 4 hours, and 

 5 of 17 postlarvae put directly into 5 -p.p.t. 

 water lived less than 3 hours. In contrast, all 

 of 17 animals placed in water of 38 to 44 p.p.t. 

 were able to survive the experimental period 

 of 3 to 4 hours. Brown shrimp apparently 

 are more sensitive to a decrease in salinity 

 than to an increase. These studies are con- 

 tinuing as part of a study on the effect of 

 salinity on oxygen consumption in shrimp. 



In a second type of study we have attempted 

 to find a chemical test that distinguishes 



31 



