Altered Larval Yellow Perch Swimming Behavior Due to Methylmercury and PCB126 Detected Using Hidden Markov Chain Models

Fish swimming behavior is a commonly
measured response in aquatic
ecotoxicology because behavior is considered a whole organism-level
effect that integrates many sensory systems. Recent advancements in
animal behavior models, such as hidden Markov chain models (HMM),
suggest an improved analytical approach for toxicology. Using both
new and traditional approaches, we examined the sublethal effects
of PCB126 and methylmercury on yellow perch (YP) larvae (Perca flavescens) using three doses. Both approaches
indicate larvae increase activity after exposure to either chemical.
The middle methylmercury-dosed larvae showed multiple altered behavior
patterns. First, larvae had a general increase in activity, typically
performing more behavior states, more time swimming, and more swimming
bouts per second. Second, when larvae were in a slow or medium swimming
state, these larvae tended to switch between these states more often.
Third, larvae swam slower during the swimming bouts. The upper PCB126-dosed
larvae exhibited a higher proportion and a fast swimming state, but
the total time spent swimming fast decreased. The middle PCB126-dosed
larvae transitioned from fast to slow swimming states less often than
the control larvae. These results indicate that developmental exposure
to very low doses of these neurotoxicants alters YP larvae overall
swimming behaviors, suggesting neurodevelopment alteration.