With respect to both genetic and nongenetic adaptations to tem- 

 perature, one may differentiate between resistance adaptations (varia- 

 tions in tolerance to extreme salinity or temperature) and capacity 

 adaptations (variations in performance within tolerated ranges) . 

 These two types of adaptations are closely related and may occur 

 simultaneously in one and the same individual. 



Osmoregulators 



Organisms that can maintain internal concentrations different 

 from that of the concentration in the outside medium and can with- 

 stand wide environmental changes. On the other hand osmoconformers 

 cannot regulate in a medium that is more dilute or more concentrated 

 than their internal concentration with the result that their body 

 fluids reach a concentration approximately equal to that of the sur- 

 rounding water. 



Osmotic concentration 



The total effective concentration of all solutes present in a 

 solution is osmoconcentration. It is often expressed in osmoles, 

 i.e., the total num.ber of moles of solute per liter of solvent. The 

 units mOsm used in this report are the number of millimoles of sol- 

 ute per kilogram of solvent. 



Salinity 



"The total amount of solid material in grams obtained in one kilo- 

 gram of seawater, when all the carbonate has been converted to oxide, 

 the bromide and iodine replaced by chlorine, and all the organic mat- 

 ter completely oxidized." (Sverdrop, Johnson and Fleming 1942). 



Serum 



The liquid which remains after allowing either whole blood or 

 plasma to clot. 



A3 



