Lethal and sublethal impacts of pyrethroid insecticides on amphibian embryos and tadpoles

Abstract

Abstract Amphibian populations are potentially sensitive to aquatic contaminants such as pesticides. We exposed embryos and larvae of five amphibians (the frogs Rana sylvatica, Rana pipiens, Rana clamitans; the toad Bufo americanus; the salamander Ambystoma maculatum) to one or both of the pyrethroid pesticides permethrin and fenvalerate. Concentrations ranged from 0.01 ppm to 2 ppm, and exposures lasted 22 or 96 h. No significant mortality of embryos, anuran tadpoles, or salamander larvae occurred during or following exposure to pyrethroids. However, tadpole growth was delayed following exposure, and tadpoles and salamander larvae responded to prodding not by darting away but by twisting abnormally. Both effects may result in greater vulnerability to predation. Recovery of normal avoidance behavior occurred more rapidly at 20 than at 15°C and following exposure to lower concentrations of the pesticides, indicating both temperature and dose effects. Tadpoles exposed later in development did not feed for a period of days following exposure but were still capable of metamorphosis. Of the five tested species, Ambystoma maculatum, a tadpole predator, was particularly sensitive. An amphibian community is therefore likely to be sensitive to low-level contamination events.