Chronic, dietary polybrominated diphenyl ether exposure affects survival, growth, and development of Rana pipiens tadpoles

Abstract

Levels of polybrominated diphenyl ethers (PBDEs) in the environment have been increasing rapidly over the past two decades; however, the toxicology of these compounds to aquatic organisms is poorly understood. Because amphibians play a role in both aquatic and terrestrial food webs, and are currently undergoing worldwide population declines, it is of interest to determine how PBDEs may affect amphibian health. This is the first study that reports chronic, dietary effects of environmentally relevant levels (7-277 ng/g wet food) of PBDEs in amphibians throughout larval development. Beginning at the free-swimming stage (Gosner Stage [GS] 25), Rana pipiens tadpoles were orally exposed to a technical pentabromodiphenyl ether mixture (DE-71) through metamorphic climax (GS 42). On exposure day 43, a subset of tadpoles was removed for body residue analysis. Sum PBDEs in whole-body tissue correlated linearly to dietary concentrations with BDE-99 represented as the highest contributing congener in both diet and tissue. Survival among all treatments compared to the control was decreased by DE-71 exposure. Further, growth and development were delayed in all but the highest treatment, perhaps indicating greater PBDE tolerance among those individuals that survived the highest treatment. Time to metamorphic climax was delayed, on average, 22 to 36 d in DE-71-treated tadpoles compared to control tadpoles. Additionally, size at metamorphosis was smaller in the highest treatment, suggesting that individuals that survived and metamorphosed similarly to the controls did so with a trade-off in size. At environmentally relevant levels, PBDEs induced mortality as well as sublethal effects on developing tadpoles through dietary exposure.

Warmer temperature modifies effects of polybrominated diphenyl ethers on hormone profiles in leopard frog tadpoles (Lithobates pipiens)

“…Endocrine alterations due to brominated compound exposure are consistent with previous studies from our laboratory, showing that northern leopard frog ( Lithobates pipiens ) tadpoles exposed via their diet to environmentally relevant concentrations of PBDEs, throughout larval development, showed diminished growth and delayed metamorphosis , altered gonadal development , and altered immune function . Developmental impairments such as inhibited tail resorption and delayed metamorphosis were also observed in Xenopus laevis exposed to the commercial PBDE mixture DE‐71 .…”

“…Doses used in the present study were chosen based on these concentrations. Nominal dietary concentrations of DE‐71 (0 ng, 6 ng, and 37 ng DE‐71/g diet wet weight) were incorporated into the food, prepared according to Coyle and Karasov and Gleason et al . Briefly, stock DE‐71 (100 μg/mL in toluene) was dissolved in acetone (equal parts weight/volume) and mixed with ground rabbit chow (250 g/L; Harlan Teklad, catalog 2030).…”

“…We performed limited chemical analyses to confirm exposure differences, and several earlier studies demonstrated that PBDE kinetics are first order and rapid enough that tissue concentrations in tadpoles exposed for 34 d (the day of exposure we chose to collect the samples) correspond closely to those in the diets (; W. Karasov, unpublished data). Diet and tissue samples were sent to ALS Environmental, ALS Group USA to measure PBDE concentrations.…”

Altered thyroid hormone levels affect body condition at metamorphosis in larvae of Xenopus laevis

“…Amphibians play an important role in both aquatic and terrestrial ecosystems, and are currently the most threatened group among all vertebrates (Stuart et al, ). Therefore, it is essential to understand how different environmental stressors affect amphibian metamorphosis and body condition by altering TH levels (Cary Coyle & Karasov, ). In this study, we demonstrate that increased or decreased TH levels as caused by different environmental stressors affect metamorphic traits and body condition in tadpoles of X. laevis in different ways.…”

“…Beside SP as the ED, Karaoglu, Kutrup, and Ogut () could show the effect of environmentally relevant concentrations of ammonium nitrate fertilizer on metamorphic traits in tadpoles of the marsh frog ( Pelophylax ridibundus ). Cary Coyle and Karasov () showed the inhibiting effect of polybrominated diphenyl ethers on anuran metamorphosis. Consequently, contaminated breeding ponds may lead to large but old metamorphs.…”