Effects of fluoride on morphology, growth, development, and thyroid hormone of Chinese toad (Bufo gargarizans) embryos

Abstract

Excessive fluoride in natural water ecosystem has the potential to detrimentally affect amphibians, but little is known of such effects or underlying mechanisms in Bufo gargarizans embryos. In the present study, the effects of fluoride exposure on B. gargarizans embryos were investigated. First, fluoride teratogenic experiment showed that the 9 days EC of fluoride on B. gargarizans embryos was 177.62 mg/L. Then, we studied the sublethal effects of fluoride on B. gargarizans embryos at control, 0.7, 4.1, 19.6, 41.9, and 62.7 mg/L fluoride concentration. Malformation, growth, and development of embryos were monitored, and type 2 and 3 iodothyronine deiodinase (Dio2 and Dio3), thyroid hormone receptors (TRα and TRβ) mRNA levels were measured. Our results showed the morphological malformations, such as tail curvature (lordosis), edema, cuticularized ciliated cells, and hyperplasia were occurred during fluoride exposure. Growth and development were all inhibited at 19.5, 41.9, and 62.7 mg/L fluoride-treated groups after 9 days' exposure. According to real-time PCR results, exposure to fluoride upregulated Dio3 and TRβ mRNA expression and downregulated Dio2 and TRα mRNA level. All above indicated that excessive fluoride could induce morphology malformations, inhibit embryonic growth and development, and disrupt the normal function of maternal thyroid hormone in B. gargarizans embryos. Environ. Mol. Mutagen. 59:123-133, 2018. © 2017 Wiley Periodicals, Inc.

Anuran tadpoles inhabiting a fluoride-rich stream: diets and morphological indicators

“…Our results showed that the total length of tadpoles of B. cordobae was not influenced by the larval stage. Therefore, the shortest total length recorded in larvae of the HF-CN stream could be due to high concentrations of fluoride, due to is a sensitive parameter a the effects of fluoride (Goh and Neff, 2003; Zhao et al., 2013; Chai et al., 2017; Pollo et al., 2016; Zhang et al., 2018). For example, Chai et al.…”

“…(2017) found that total length of embryo of Rana chensinensis (Chordata, Ranidae) decreases with increasing levels of fluoride (≥0.7 mg F/L). The specific mechanism of inhibition may be the accumulation of fluoride in the body, which causes an imbalance in bone deposition and the remodeling activities that lead to skeletal fluorosis (Zhang et al., 2018). In addition, the metamorphosis of the tadpoles is delayed in the presence of high concentrations of fluoride (Chai et al., 2017).…”

“…In recent years, concern about deleterious consequences of fluoride on several organisms has been developed (Zuo et al., 2018) and especially its potential toxicity to aquatic organisms (Shi et al., 2013; Ballarin et al., 2014; Camargo and Alonso, 2017; Zhang et al., 2018). Fluoride is a non-metallic halogen abundant in the environment, distributed only in combination with other elements as fluoride compounds (Camargo, 2003).…”

“…This mineral may reach freshwater ecosystems from natural sources that include weathering of fluoride minerals (Weinstein and Davison, 2004) and/or anthropogenic sources (Camargo, 2003; Weinstein and Davison, 2004). For these reasons, there is a worldwide concern about the increase of fluoride levels in freshwater ecosystems (Zhang et al., 2018). Alterations occurring in aquatic organism exposed to fluoride have been the topic of several studies, most of them based on laboratory exposures (Camargo, 2003; Shi et al., 2013; Ballarin et al., 2014; Camargo and Alonso, 2017; Zhang et al., 2018).…”

“…For these reasons, there is a worldwide concern about the increase of fluoride levels in freshwater ecosystems (Zhang et al., 2018). Alterations occurring in aquatic organism exposed to fluoride have been the topic of several studies, most of them based on laboratory exposures (Camargo, 2003; Shi et al., 2013; Ballarin et al., 2014; Camargo and Alonso, 2017; Zhang et al., 2018). However, there is limited information on the ecotoxicity of fluoride on trophic ecology of anuran tadpoles (Chai et al., 2016a,b).…”