Table 10 

 Effect of Petroleum on Nauplii of Balanus amphitrite niveus (1 hour experiments). 



Explanation. D.^, Concentration (as percentage of oil stock solution) at which half 

 the larvae were present in the bottom of the experimental tube 

 after Ih. 

 1 Behavior of larvae in the bottom fraction. Approximate threshold concentrations 



for, A, all larvae swimming; B, barely swimming or few swimming; C, mostly 



dead. 



is a study of the pelagic pteropod Creseis acicula, of which large num- 

 bers were used to test the toxic effects of No. 2 fuel oil Exxon (Bay- 

 town). Concentrations of 0.4 ppm and more were toxic, reducing 

 survival; mortalities increased at higher concentrations and with 

 duration of exposure (Figs. 6 and 7). At concentrations of 0.2 ppm, 

 pteropods retracted and ceased to swim; at lower concentrations, swim- 

 ming activity continued normally, at least for the first 24h. 



The chemical senses are very important in the feeding and activi- 

 ties of fishes, such as orientation, species recognition, etc. With a view 

 to exploring damping of chemical senses by petroleum, sea catfishes 

 (Arius felis) were exposed to fuel oil for several days. Overt activity 

 was watched and electrocardiograms were recorded, since slight 

 changes in environmental conditions have been found to be reflected 

 in changes of cardiac activity. It was found that low concentrations 

 of petroleum oils, 0.2 ppm, caused a temporary slowing of heart beat, 

 fish made exploratory efforts to escape from their containers. During 

 prolonged exposure fish succumbed, but feeding among the survivors 

 was not interrupted. However, the fish were unable to retain their 

 food, and their gills and fins became seriously damaged. 



The experiments with animals have shown that the various crude 

 oils and petroleum derivatives differ greatly in toxicity. Southern 



33 



