Neurophysiology 



The preliminary results from neurophysiological experiments on the 

 lobster's olfactory chemoreceptors are presented with a few examples in Figure 

 10-4. Details are provided in the figure legend. These examples show that (1) 

 the water-accommodated fraction of #2 fuel oil itself can be perceived as a 

 stimulus by the primary receptor cells, (2) that the presence of oil in a mussel 

 juice food stimulus can change the response pattern of the small nerve bundle, 

 and (3) that exposure to oil causes abnormal bursting patterns (See Figure 

 10-4). 



Generally, differences in chemoreceptor responses between mussel and 

 mussel-plus-oil are more distinct in oil-exposed lobsters than in controls. One 

 other striking feature is the tendency of oil-exposed individuals to exhibit 

 irregular bursts, or frequent small clusters, of spikes, both spontaneously and in 

 response to stimuli (Figure 10-4), This may be a general injury response (6) 

 here caused by oil exposure. However, it has also appeared in nerves from 

 animals which were exposed to very low levels of oil (0.3 ppm) in response to 

 mussel-plus-oil stimuli, but not to mussel alone. 



DISCUSSION 



Our experiments have shown thus far that the original hypothesis that oil 

 pollution may interfere in a number of different ways with chemoreception, 

 and hence marine animal behavior, is not unreasonable. Behavioral experiments 

 on the efficiency of the lobster's chemically mediated feeding behavior have 

 shown that exposure to #2 fuel oil (WAF) causes significant delays after five 

 days at exposure levels as low as 0.08 and 0.15 ppm. Increased dosage caused 

 increasingly severe effects. Also behavioral recovery was a function of exposure 

 level. At higher exposures (1.5 ppm) serious neuromuscular abnormalities 

 appeared within 30 hours. Lobsters showed great individual differences in 

 behavioral effects and recovery. The range of exposure levels where behavior 

 was affected, but no serious neuromuscular defects appeared, proved to be 

 surprisingly narrow. However, further experiments are required for complete 

 documentation of this point. 



Parallel neurophysiological experiments on the effects of such exposures on 

 chemoreceptor performance showed that the receptors perceive oil as a 

 chemical stimulus, that the presence of oil could modify normal responses, and 

 that oil-exposed lobsters ofen showed abnormal receptor activity, both 

 spontaneously and in response to food stimuli. 



Based on these results, it appears that #2 fuel oil (WAF) interferes with 

 lobster behavior in a number of ways. At low exposure levels (0.1 ppm range), 



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