UBC Theses and Dissertations
Examining the impacts of pesticide exposure on the survivorship and development of the Great Basin Spadefoot (Spea intermontana) and the Pacific Treefrog (Pseudacris regilla) in a laboratory environment de Jong Westman, Alexandra
Amphibian populations are declining globally, and pesticides have been suggested as one of the contributing factors. Field experiments involving ponds immersed in agricultural environments have been observed to have dramatically lower biodiversity and amphibian abundance than ponds located in non-agricultural settings. There has been much work involving in situ pond experiments, and a plethora of laboratory pesticide experiments often involving test concentrations much higher than those observed in the field. To determine which pesticides impact amphibian embryo survivorship and tadpole development, three insecticides currently used in British Columbia were tested at their detected field concentrations in a laboratory environment. The commercial formulations of endosulfan, azinphos-methyl and diazinon were tested alone and in combination. Embryos of the Great Basin Spadefoot (Spea intermontana and Pacific Treefrog (Pseudacris regilla) were collected from reference sites in the South Okanagan of BC, and transported to a federal government laboratory facility in North Vancouver, BC. Here, 8-day LC20 experiments were conducted on the young embryos and young tadpoles with the following toxicological endpoints: acute mortality, behavioral abnormalities, morphological abnormalities and developmental abnormalities. Overall, endosulfan (LC20₈d = 77.1 ng/L) was the most toxic pesticide to both species in the tadpole stage, causing acute mortality, behavioral abnormalities and morphological abnormalities. Embryos were observed to be very resilient to the low test concentrations of endosulfan, with the majority of mortalities occurring post-hatch (LC20₈d = 2872.7 ng/L). The second most toxic insecticide was found to be azinphos-methyl (LC20₈d > 50 000 ng/L); and lastly, diazinon was found to be the least toxic (LC20₈d > 175 000 ng/L) to both life stages of amphibians. In addition to acute mortality, several behavioral abnormalities arose in the tadpoles exposed to endosulfan, including extreme agitation in both species of amphibians, tail kinking and melanophore aggregation in P. regilla tadpoles.
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