Variation in the transcriptome response and detoxification gene diversity drives pesticide tolerance in fishes

Pesticides are critical for invasive species management, but often have negative effects on non-target native biota. Tolerance to pesticides should have an evolutionary basis, but this is poorly understood. Invasive sea lamprey (Petromyzon marinus) populations in North America have been controlled with a pesticide lethal to them at lower concentrations than native fishes. We addressed how interspecific variation in gene expression and detoxification gene diversity confer differential pesticide sensitivity in two fish species. We exposed sea lamprey and bluegill (Lepomis macrochirus), a tolerant native species, to TFM, a pesticide commonly used in sea lamprey control, and used whole-transcriptome sequencing of gill and liver to characterize the cellular response. Comparatively, bluegill exhibited a larger number of detoxification genes expressed and a larger number of responsive transcripts overall, which likely contributes to greater tolerance to TFM. Understanding the genetic and physiological basis for pesticide tolerance is crucial for managing invasive species.

Performance studies on jumping behaviour in froglets exposed to commercial grade malathion

Aim: Behavioural changes of an organism are used as an indicator to assess the impact of neurotoxic compounds. Jumping performance of newly emerged froglets exposed to malathion at their tadpole stage was studied. Methodology: Tadpole groups were exposed to 1226, 2453 and 6133 µg l-1 malathion in laboratory mesocosms. When they emerged as froglet, their jumping performance was studied. Results: As malathion is an AChE inhibitor and produces negative effect on survival of tadpoles, we anticipated increased malathion exposure could result in reduction of jumping distance in metamorphs. However, as compared to control, the jumping distance increased with malathion concentrations and showed significant increase in the individuals treated with the highest concentration of malathion (LC25; F3,21 = 11.41, p = 0.0001). Interpretation: Malathion is toxic to tadpoles; however, it could result in concentration dependent jumping performance within the tested concentrations. Several other factors like tadpole density, temperature of the media, pesticide tolerance may act as determining factor, which requires further investigations.