Effect of Atrazine On Olfactory-Mediated Behaviors On Pacific Lamprey

Pacific lamprey (Entosphenus tridentatus) are experiencing population declines throughout their range.  Xenobiotics could be an important risk factor for lamprey populations.  Our goal was to establish if common herbicides, as used in forest management, could affect reproductive fitness.  We determined that atrazine was a likely the compound of greatest concern to lamprey populations.  Using an odorant response behavioral assay we were able to demonstrate that environmentally relevant concentrations of atrazine caused a depressed response to adult lamprey holding tank effluent, likely pheromone.  Atrazine also depressed their activity level, the number of times they crossed into the effluent arm after being treated with atrazine was significantly lower than controls.  In addition, activity level post exposure to atrazine differed between adult life history stages, something that was not significantly different during control trials.  Using an odorant detection assay, based on evaluating breathing rate, we were able to show that environmentally relevant concentrations of atrazine caused a significant increase in respiratory response to a repulsive odorant from a conspecific necromone.  Through the detection study we also showed that lamprey, exposed to atrazine, had a slight increase in respiratory response to odor from adult lamprey.  If we are concerned about the decline in Pacific lamprey populations, then we should be concerned with their exposure to atrazine in the environment.