Adverse effects of sodium fluoride exposure on the development, thyroid morphology and disease resistance in rainbow trout (Oncorhynchus mykiss) embryos and larvae.

Abstract

Endocrine disruptors, ubiquitous in terrestrial and aquatic environments, have come under increased public and scientific scrutiny and are classified as substances of great concern for human health and the environment. The main objective of which is to determine the potential role of sodium fluoride (NaF) on rainbow trout health, with a particular interest in the thyroid hormone system, the immune system, and the development and behavior in early life stages. Rainbow trout (Oncorhynchus mykiss) embryos (265DD) were exposed for 15 days to NaF at 0, 0.5, 1, 5, 8 and 15 mg/L of F. After the first 15 day-exposure, larvae were divided into three batches (1) exposed to NaF for further 8 days at the same concentrations, (2) infected with the Infectious Hematopoietic Necrosis virus, or (3) held in clean water. Fish were monitored daily to follow their development, morphology and behavior and sampled after 15 or 23 days of exposure, with and without viral infection, to evaluate effects on the THS (eye development, thyroid) and their capacity of resistance to IHNV. Results show impaired growth (decrease in size and an increase in the rate of abnormalities rate) and significative behavior impact at 15 mg/L of Fwith a decrease of activity (speed, and light stress reaction). 5 mg/L of Fcaused delayed hatching, a decrease in virus-related mortality, an increase of thyroid follicles number, and increased photoreceptor layer thickness. Further analyses will determine the immunotoxicity of this potential ED by analyzing gene activity and blood parameters in older fish.