Environmentally relevant concentrations of ammonium perchlorate inhibit development and metamorphosis in Xenopus laevis

Abstract

We determined whether environmentally relevant concentrations of ammonium perchlorate alter development and metamorphosis in Xenopus laevis. Eggs and larvae were exposed to varying concentrations of ammonium perchlorate or control medium for 70 d. Most treatment-related mortality was observed within 5 d after exposure and was due in large part to reduced hatching success. The 5- and 70-d median lethal concentrations (LC50s) were 510 +/- 36 mg ammonium perchlorate/L and 223 +/- 13 mg ammonium perchlorate/L, respectively. Ammonium perchlorate did not cause any concentration-related developmental abnormalities at concentrations below the 70-d LC50. Ammonium perchlorate inhibited metamorphosis in a concentration-dependent manner as evident from effects on forelimb emergence, tail resorption, and hindlimb growth. These effects were observed after exposure to ammonium perchlorate concentrations in the parts-per-billion range, at or below concentrations reported in surface waters contaminated with ammonium perchlorate. Ammonium perchlorate significantly inhibited tail resorption after a 14-d exposure in the U.S. Environmental Protection Agency (U.S. EPA) Endocrine Disruptor Screening and Testing Committee (EDSTAC) Tier I frog metamorphosis assay for thyroid disruption in amphibians. We believe that ammonium perchlorate may pose a threat to normal development and growth in natural amphibian populations.

Effects of Ammonium Perchlorate on Thyroid Function in Developing Fathead Minnows, Pimephales promelas

“…Exposure of fathead minnow embryos to ammonium perchlorate had no significant effect on their hatching, in agreement with a similar lack of effect of ammonium perchlorate on hatching by the amphibian Xenopus laevis at concentrations of < 1,000 mg/L (Goleman et al 2002). Thereafter, however, exposure to ammonium perchlorate resulted in developmental retardation, both in X. laevis , where a reduced snout to vent length was observed after 16 days exposure of larvae to 425 mg/L ammonium perchlorate (Goleman et al 2002), and in the present studies of fathead minnows exposed to 10 and 100 mg/L ammonium perchlorate.…”

“…Thereafter, however, exposure to ammonium perchlorate resulted in developmental retardation, both in X. laevis , where a reduced snout to vent length was observed after 16 days exposure of larvae to 425 mg/L ammonium perchlorate (Goleman et al 2002), and in the present studies of fathead minnows exposed to 10 and 100 mg/L ammonium perchlorate.…”

“…In the amphibian Xenopus laevis , 5 μg/L perchlorate inhibited forelimb emergence during thyroid-dependent metamorphosis (Goleman et al 2002), and at 18 μg/L significantly fewer Xenopus completed tail resorption. Metamorphosis of larval sea lamprey Petromyzon marinus (an agnathan fish) is also affected by exposure to perchlorate (Manzon and Youson 1997, 2002; Manzon et al 2001), but only two studies have investigated the impact of perchlorate on teleost fish that form key components of freshwater ecosystems.…”

Peer Reviewed: Wildlife Toxicology Revisited

“…Recently, perchlorate, a thyroid hormone inhibitor, gained national attention due to its widespread distribution in groundwater and surface water supplies. Figures 1 and 2 (also, see photo below) show how perchlorate detected in numerous plant, fish, and wildlife species (16) can effectively inhibit metamorphosis and shift sex ratios in amphibians (17,18). As endocrinealtering chemicals continue to emerge, the demand for studies to examine their effects on wildlife will increase.…”

Acute Toxic Effects of Cadmium in Larvae of the Green Toad, Pseudepidalea Variabilis (Pallas, 1769) (Amphibia: Anura)

“…There are several hypotheses about the possible reasons behind this phenomenon (3,4). Some of these hypotheses include impact of urbanization due to rapid increase in settlements and industrialization, chemical pollution, habitat degradation/destruction, and diseases (5)(6)(7)(8). Among these, the destruction of habitats and increased pollution significantly threaten the survival of amphibians, which spend their embryonic and larval stages exclusively in water and play a significant role in biomonitoring programmes (9)(10)(11).…”