Evaluation of the developmental toxicity of metal‐contaminated sediments using short‐term fathead minnow and frog embryo‐larval assays

Abstract

The effects of metal‐contaminated sediment extracts and a reference toxicant (zinc sulfate) were determined by examining the developmental morphology, growth and mortality of exposed fathead minnow (Pimephales promelas) and frog (Xenopus laevis) embryos. Sediments from two contaminated stream sites were extracted with reconstituted culture water at various pH values for 24 h. Developmental toxicity tests were performed using the frog embryo teratogenesis assay‐Xenopus (FETAX) protocol. The results suggest that Zn was the major developmental toxicant in the sediment extracts. The measured Zn concentration in the sediment extracts that caused malformation in 50% of the fish embryos (EC50) was 0.5 to 1.4 mg/L (normalized to 100 mg/L hardness). EC50 values for the reference toxicant tests were 0.6 and 0.8 mg/L Zn. The frog embryo EC50 for the extracts ranged from 2.2 to 3.6 mg/L Zn and was 3.6 mg/L Zn in the reference toxicant test. In 67% of the tests, malformation was a more sensitive endpoint than growth inhibition. Mortality was the least sensitive endpoint, that is, the LC50s in the reference toxicant tests were 3.6 mg/L Zn for the fathead minnow and 34.5 mg/L for the frog. The extraction procedure may be useful for determining potential toxicity in the event metals are leached from aquatic sediments by dredging or acidification.

The effects of zinc chloride during early embryonic development in zebrafish (Brachydanio rerio)

“…In 8-day tests with fathead minnow, the LD 50 value for Zn 2+ was 0.04 mg/L (7), and in 6-day tests for the same fish, the LD 50 value for Zn 2+ was 3.6 mg/L. In 4-day tests with frog embryos, the LD 50 value was 34.5 mg/L (19).…”

“…Zebrafish have been used predominantly in developmental biology, developmental toxicology, teratology, molecular genetics, and neurotoxicology studies, but their value in toxicology as well as drug discovery has also been recognized. To evaluate the toxicity of a chemical, it is essential to identify the endpoints of toxicity and their dose-response relationships, elucidate the mechanisms of toxicity, and determine the toxicodynamics of the chemical (11,12,(16)(17)(18)(19)(20)(21)(22). Nagel performed embryo tests with the zebrafish Danio rerio (DarT) as a general model.…”

Zinc Contamination Is an Underestimated Risk to Amphibians: Toxicity Evaluation in Tadpoles of Fejervarya Limnocharis

“…Therefore, it is evident that there exists species specific sensitivity among different anuran species to a given toxicant. Morphological and physiological abnormalities in amphibians exposed to toxicants have been well-studied (Stebler et al, 1988;Bantle et al, 1989;Hopkins et al, 2000). However, the mechanisms by which zinc influences amphibian metamorphosis remain unclear.…”