Response to Light 



Nauplii used in all experiments were light adapted as fluorescent bulbs in 

 the temperature boxes were on continuously. When transferred to the darkfield 

 stage, larvae tended to disperse to the beaker walls with ceiling Hghts on. With 

 these lights extinguished, naupHi tended to swim away from the beaker walls. 

 Direction of travel upon entering or leaving the camera field exhibited no 

 particular orientation. Ongoing studies indicate dark adapted B. amphitrite 

 nauplii will exhibit a weak photonegative response to substage hght over a 

 five-minute period (Forward & Lang, personal observation). 



Balanus spp. stage II nauphi exhibit similar response to sudden changes in 

 light intensity. When overhead white room lights are turned on, Balanus nauplii 

 will approximately double linear velocities, then within 4-6 seconds return to 

 initial swimming speeds (Figure 18-2). Turning overhead lights off has 

 essentially the opposite effect; nauplii will cease locomotion for about five 

 seconds and then return to initial sv^mming speeds (Figure 18-3). 



H 1- 



8 1 2 



SECONDS 



16 



20 



Figure 1 8-2. Example of running average linear velocity 

 (mm/sec) for sample of ten stage II Balanus venustus 

 nauplii exposed to sudden light increase. 



NOTE: Dashed line indicates time at which overhead white light stimulus was 

 applied. Filtered (820 nm peak transmission) substage light was present 

 throughout experiment for recording purposes. 



276 



