For 24 hour exposures, concentrations of Cu below 100 ppb were clearly 

 sublethal to the nauplii tested. Delay in development of B. improvisus nauplii 

 occurred at 50 ppb Cu and changes in swimming behavior were evident at 

 15-25 ppb Cu. At the lowest Cu test levels, responses were restricted to 

 increased MLV, but at higher sublethal concentrations MLV was depressed and 

 swimming patterns became atypical. A stimulatory effect of very low levels of 

 copper on swimming activity has also been reported for brook trout (9.5 ppb 

 Cu) (9) and with sea urchin sperm (<20 ppb Cu) (28). 



Forward and Costlow (12) also observed increased sv^mming activity of 

 crab larvae exposed to 0.1 ppm of an insect juvenile hormone mimic, although 

 larval development was not perceptively affected until 1 .0 ppm was reached. 

 On the other hand, sublethal concentrations of mercury and oil are reported to 

 depress activity of marine crustaceans at nearly all levels tested (8, 18). 

 Stebbing (23) suggests that apparent stimulatory effects of heavy metal ions on 

 growth in marine hydriods and other groups are often only temporary and may 

 represent a normal response to stressors. 



Observations on swimming of B. improvisus nauplii indicate that not only 

 the Unear velocity, but also the pattern is altered by Cu. Nauplii swimming in 

 convoluted paths (Figure 18-7) tends to increase in number in the presence of 

 copper above control levels. As copper concentrations exceed 50 ppb, paths 

 with a distinct "wobble" became evident (Figure 18-7). This latter pattern is 

 possibly a consequence of impaired or abnormal beating of appendages. This 

 would lead to reduced feeding abilities, as feeding in cirriped larvae is a direct 

 function of appendage movement. The increased development time to cyprid 

 observed at higher sublethal copper concentrations may be the result of 

 difficulties in feeding. 



The present study has consistently observed altered swimming behavior of 

 cirriped larvae at Cu concentrations far below 24 hour toxic levels. Basic 

 changes in swimming speed per se may prove useful indicators of pollution 

 stress, but also of great interest are additional effects on larval motile responses 

 to environmental stimuH or cues (light, chemical, gravity, etc.). The latter may 

 prove more meaningful in predicting safe levels of pollutants. If short-term 

 behavioral reaction can be satisfactorly correlated with long-term detrimental 

 effects, the potential exists for rapid screening of toxic levels using this motile 

 behavioral qualification technique. Further studies relating observed behavioral 

 responses to other physiological parameters, and ultimately larval success, are 

 planned. 



286 



