THE EFFECTS OF TEMPERATURE, LIGHT 
AND EXPOSURE TO SUBLETHAL LEVELS 
OF COPPER ON THE SWIMMING BEHAVIOR 
OF BARNACLE NAUPLII 
William Lang 
Sarah Lawrence 
Don C. Miller 
U.S. Environmental Research Laboratory 
Narragansett, Rhode Island 02882 
ABSTRACT 
The “Bugsystem”, a computer-television system to accurately track and 
analyze swimming patterns of aquatic organisms has been developed; video 
images of test animals are converted to time sequence X-Y coordinates to allow 
rapid computer analysis of linear or angular velocity, rate of change of 
direction, direction of travel and other parameters. Initial experiments using 
barnacle nauplii (Balanus amphitrite, B. improvisus, B. venustus, Chthamalus 
fragilis) indicate larval swimming speeds are affected by temperature and light 
regime. Response to temperature appears to be function of species tested and, 
perhaps, geographic location of adult population. Changes in linear velocity 
induced by acute light intesity variation are of short duration. Mean linear 
velocities of nauplii are altered by 24 hour exposure to copper as low as 20 
ppb. Linear velocities of exposed populations increase relative to controls at 
low copper levels, and then decrease as lethal levels are approached. Copper 
will also alter the swimming pattern of exposed larvae. 
INTRODUCTION 
In view of concern that bioassays directed solely toward determining lethal 
concentrations of pollutants may not accurately reflect levels doing harm to 
the environment, attention has been directed toward sublethal effects of 
pollutants- “effects which do not immediately, or directly, lead to death, but 
which nevertheless cause disturbances which may be of ecological significance 
(1).” Existing studies using pathological, physiological, and behavioral 
parameters indicate approximate thresholds for sublethal responses are often 
10-20 percent of LC50 levels or less (7, 22). It is generally recognized that 
behavioral responses of marine animals are often highly sensitive to stress (18) 
and that juvenile or larval stages of many marine organisms represent that part 
of the life-cycle most susceptible to stress (4, 8, 16). Logically, larval 
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