Investigating Alternative Testing Methods for the Evaluation of Acute Nickel Toxicity in Cyprinodon variegatus

Abstract

Nickel is the most prominent heavy metal in the effluents associated with crude oil extraction and production. Given that these effluents are released into the ocean, investigating the toxicity of nickel on marine life is pertinent. A current method for evaluating the toxicity of oil effluents is the sheepshead minnow larval growth and survival (LGS) test, which exposes larval fish to varying concentrations of effluents or associated single chemicals over a 7-day period. However, current legislation, like the Frank E. Lautenberg Act, requires that animal testing be refined whenever possible to enhance animal welfare. The fish embryo toxicity (FET) test, which investigates chemical toxicity using fish embryos over a 7-day exposure period, is a potential alternative method capable of meeting legislative needs related to animal welfare. THe objective of this study was to determine if a sheepshead minnow FET test is a viable replacement for the sheepshead minnow LGS test. To accomplish this, the results of the sheepshead minnow LGS and FET tests using nickel were compared. The results of this study show that there is no significant difference in mortality between testing methods, indicating that the FET should be considered as an alternative testing method to the LGS. Additionally, significant decreases in larval growth were observed in the highest concentration exposure group with 100% survival in the LGS test, indicating that nickel may cause negative effects at sublethal concentrations. While the LGS test includes measurements of growth and development, an important metric in examining effects at sublethal concentrations, evidence suggests that it may be possible to measure similar effects of development in the FET test by including sublethal metrics as FET test endpoints.