Figure 18-7. Examples of computer tracked paths for stage II 



Balanus improvisus nauplii and assigned rate of change of 

 direction values (degrees/sec): A) 114, B) 53, C) 152, D) 373. 



NOTE: Paths A, B are typical of control conditions; path C occurs more fre- 

 quently with copper present; path D was observed only above 50 ppb copper. 



DISCUSSION 



Initial results have demonstrated possible use of invertebrate larval 

 swimming behavior as a sublethal response index. It has also been shown that 

 for this index to be reliable, the effects of basic experimental variables such as 

 temperature and light regime on the svvamming response of test organisms 

 should be understood. 



Although previous studies on cirriped and brachyuran larvae (2, 11, 25) 

 indicate no phototactic response is evident above 650 nm, cirriped nauplii 

 appeared to exhibit a weak response to the present substage light. Spectral 

 sensitivity of the species tested appears to extend further into the red than 

 previously reported. 



Balanus venustiis and B. amphitrite nauplii exhibited two responses to 

 sudden changes in light. The cessation of swimming by nauplii following a 

 sudden hght decrease is similar to the "sinking response" described for 



284 



