Concentration of Petroleum R 



Figure 4. Effects of petroleum oils on activity of barnacle nauplii. Ordinate, per- 

 centage of larvae in the bottom fraction of the experimental tube; abscissa, concen- 

 tration of oil-stock (water soluble fraction). Curves A, Crankcase motor oil, B, No. 2 

 Fuel oil (API); C, Bunker C; D, Venezuelan crude; E, Alaskan crude; F. Southern 

 Louisiana crude. 



naphthalene, naphthalene, indan, 1 .2,4-triniethyl benzene, and 1,3,5- 

 trimethyl benzene. 



Larvae of crabs (hermit, spider and stone) were equally sensitive 

 to No. 2 fuel oil, which was deleterious to development and survival. 

 The most striking effects were found with stone crab zoeae, the mor- 

 tality increasing with the concentration (Fig. 5). In addition to survi- 

 val, significant differences from controls were observed in the condition 

 of the larvae and the rate of development. Higher concentrations of 

 oil retarded growth and inhibited molting of hermit and spider crab 

 larvae, the effects appearing at a concentration of 0.5 ppm. 



Larvae of benthic animals during their planktonic existence have 

 stereotyped activity patterns which lead them to suitable positions for 

 feeding and dispersal; later, when they approach metamorphosis, be- 

 havioral responses enable them to choose suitable places to settle. In- 

 terference with normal activity places larvae in jeopardy; for example, 

 barnacle larvae (nauplii) are attracted to light and swim upwards in 

 the water column; petroleum oils at low levels abolish this response 

 and, therefore, interfere with the animals' normal mechanism of dis- 

 persion. 



Most of the Texas experiments have been carried out with coastal 

 and inshore species, which are more readily available, but the inves- 

 tigations are being extended to offshore pelagic species. An example 



32 



