Alterations in schooling, shoaling, and startle response behaviors in
mummichog, Fundulus heteroclitus, resulting from exposures to the
harmful algal bloom neurotoxins, brevetoxin and saxitoxin
J.D. Salierno1 and A.S. Kane1,2
1Aquatic Pathobiology Laboratory, Department
of Veterinary Medicine, University of Maryland, College Park, MD, USA
2Virgina-Maryland Regional College of Veterinary Medicine, College Park,
MD, USA
Harmful algal blooms (HABs) in the mid-Atlantic United States, and associated
observations of fish morbidity and mortality, have increased in frequency
and severity over the past several decades. The ability to predict and
characterize environmental effects of different HAB species is essential
to HAB remediation and control. This study investigated the exposure effects
of relevant, low-level HAB neurotoxins on swimming behavior of twelve
groups of 5 mummichog, Fundulus heteroclitus. These neurotoxins included
saxitoxin (STX, 100 and 150 µg/L) and brevetoxin (PbTx-2, 40 and
55 µg/L). Thirty-minute video segments before, during, and after
neurotoxin exposure were captured using a videography system (Videoscript
Professional©, v. 3.1) and were evaluated using software designed
for the analysis of interactions, schooling and shoaling behaviors. Predator
avoidance (overhead visual bird model) and startle response (auditory/vibratory
stimulus) behaviors in groups of mummichog were compared before and after
toxin exposure. In an attempt to link behavioral alterations with neuronal
signaling in the brain, changes in brain activity resulting from STX and
PbTx-2 exposure were quantified using neuronal c-Fos expression. Mummichog
groups exposed to both concentrations of STX showed significantly decreased
interactions (50%) as well as decreased schooling and shoaling frequencies.
Fish exposed to both concentrations of PbTx-2 showed increased interactions
(30%) and schooling frequency (25%). Shoal and aggregation size significantly
decreased after exposure to both HAB toxins. Additionally, exposure to
both toxins significantly altered specific components of startle- and
predator response behaviors. The c-Fos neuronal activity assay revealed
similar results, whereby STX exposure significantly decreased brain activity
while PbTx-2 increased brain activity. These behavioral and neuronal alterations
further confirm the known paralytic and excitatory actions of STX and
PbTx-2. These results suggest that sub-lethal exposure to HAB toxins can
have demonstrable effects on swimming and social behaviors, startle response
and predator avoidance behaviors, and brain activity. This is the first
study to documents alterations in social behavior of fish exposed to HAB
toxins. This data will provide a better understanding how environmentally
realistic concentrations of HAB stressors affect fish behavior.
Paper presented
at Measuring Behavior 2005
, 5th International Conference on Methods and Techniques
in Behavioral Research, 30 August - 2 September 2005, Wageningen, The
Netherlands.
© 2005 Noldus
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