Effects of low concentrations of forest‐use pesticides on frog embryos and tadpoles

Abstract

Management of coniferous forests of eastern Canada may involve spraying with the insecticide femtrothion and the herbicides triclopyr and hexazinone Because ranid frogs breed in ponds that are unavoidably contaminated by spraying, we measured the toxicity of these chemicals to embryos and tadpoles of Rana pipiens (leopard frog), Rana clamitans (green frog), and Rana catesbeiana (bullfrog) under lab conditions Embryos were exposed during late neurula stage and tadpoles within 48 h after hatching to femtrothion (24 h, 0 5‐8 0 ppm), tnclopyr (48 h, 0 6‐4 8 ppm), and hexazmone (8 d, 100 ppm) We measured hatching success of embryos, and for tadpoles, mortality, ability to swim away when prodded, and total body length one week after exposure Hexazinone had no effects on embryos or tadpoles, even at the unreasonably high levels to which they were exposed Hatching success of embryos and subsequent avoidance behavior were unaffected in all species by exposures to triclopyr and femtrothion Newly hatched tadpoles of all species were very sensitive to 2 4 and 4 8 ppm tnclopyr and to 4 0 and 8 0 ppm femtrothion, either dying or remaining paralyzed following exposure Tadpoles initially affected by exposure to lower concentrations of femtrothion or tnclopyr usually recovered within 1 to 3 d Bullfrog and green frog tadpoles appear to be more sensitive than leopard frog tadpoles, and bullfrog tadpoles were consistently more sensitive than green frog tadpoles

Decline of a Tropical Montane Amphibian Fauna

“…In any case, of the three common chemicals sprayed on the apple orchards at Las Tablas, two (Mancozeb and Belnate) are known to have reproductive and endocrinedisrupting effects (Colborn et al 1993), and all six dead or dying individuals were females. Amphibian species exhibit different responses to a variety of pesticides (Berrill et al 1994); if a site were contaminated by pesticides, different species might exhibit different symptoms and susceptibility. Pounds and Crump (1994) propose that amphibian declines at Monteverde are due to a synergistic effect between climate change and environmental contamination.…”

Effects of herbicide treatments on biotic components in regenerating northern forests

“…However, three and four years after treatment, soil-dwelling gastropod abundance was similar in soils collected from herbicide-treated (377/m 2 ) and control plots (258/m 2 ) (Prezio 1997). (Table 3) Published work examining effects of conifer release with herbicides on amphibians and reptiles is limited to laboratory studies with frog embryos and tadpoles (Berrill et al 1994), studies in the Oregon Coast Range (Cole et al 1997), and field and laboratory work in Ontario (Bogart et al 1995.…”

“…In the laboratory, Berrill et al (1994) examined responses of embryos and tadpoles of the leopard frog (Rana pipiens), green frog (Rana clamitans), and bullfrog (Rana catesbeiana) to fenitrothion (an insecticide) and two active ingredients (hexazinone, triclopyr) found in herbicide products. Hexazinone had no effect on embryos or tadpoles even at exposure levels dramatically higher than amphibians would experience in the wild.…”

Aquatic Fate of Aerially Applied Hexazinone and Terbuthylazine in a New Zealand Planted Forest

“…Both hexazinone and its metabolites (A-H) are mobile and can persist in some aquatic environments (Tu et al, 2001). Hexazinone can be highly toxic to algae but it is of low toxicity to aquatic invertebrates and fish (Table 1) (Berrill et al, 1994;Kreutzweiser et al, 1995;NievesPuigdoller et al, 2007). Due to its high water solubility, hexazinone does not bioaccumulate and has a low BCF factor (Table 1).…”