Fluoride Is The Impact Of Of Toad Larval Development

Fluorine is one of the most abundant chemistry elements in the earth. Because of its great reactivity, fluorine cannot be found in nature in its elemental state. It exists either as inorganic fluorides (including the free anion F-) or as organic fluoride compounds (e.g., Freon). Fluorinion can be ingested by people mainly from the drinking water, beverages and food. As is known to all, fluoride is the most important caries-preventive agent in dentistry. In many countries, water fluoridation is the controlled addition of fluoride to a public water supply to reduce tooth decay. However, the toxicity of fluoride has also been reported.With the development of industry, a mass of fluoride was produced by human activities, such as metallurgy, production of brick, ceramics and glasses, and processing of nuclear fuel and manure, which cause the increase of the fluoride concentration in the air. Therefore, organisms become easier to be exposed to the fluoride. Acute and chronic toxicity can be caused by the fluoride exposure to the organism. In this paper, we have studied the acute exposure to fluoride on the Big Toad Bufo gargarizans and the effect of fluoride on the development of the larvae at sublethal concentration. The effect of fluoride on the development of anura larvae were investigated using morphological measurement, development staging, biochemical method, histological and immunohistochemistry method. The main results are as follows:1. Exposure at a high concentration of fluoride (>500 mg/L) may lead to lethal effect. The 24h,48h,72h and 96h median lethal concentration (LC50) values of fluoride to larval B. gargarizam were 693.02mg/L,660.57mg/L,643.12mg/L and 622.81 mg/L respectively. The safe concentration of fluoride in water for larval B. gargarizans is determined to be 6.2281 mg/L.2. Exposure at a high concentration of fluoride (>500 mg/L) may cause the cell apoptosis and even necrosis. The DNA ladder was detected in the acute toxicity of fluoride, which shows the genetoxic of fluoride.3. After exposure to fluoride at sublethal concentration, the metamorphic data, such as body weight (BW). total length (TOL) and percentage of metamorphosis frog (PMF) were evaluated in order to reveal the effect of fluoride on the larval development. The results showed that advanced metamorphosis can be observed with an exposure at a low concentration of fluoride (≤5.00 mg/L). However, long-term exposure to high fluoride (≥10.00 mg/L) may stunt growth of the larvae.4. The effect of fluoride on oxidative stress was studied by investigating the activity of antioxidant system. It can be observed that high oxidative stress was taken place with high concentration fluoride (≥10.00 mg/L) exposure. Activity of enzymes can be inhibited or enhanced after long-term exposure to fluoride, which indicated the fluoride is a potent enzyme poison.5. The double-stained method with alcian blue and alizarin red were used to investigate the skeletal development of the larvae. The results showed that exposure to fluoride at high concentration may lead to the osteoporosis. The concentration of calcium and chondroitin sulfate were decreased in the groups of high fluoride (≥10.00 mg/L).6. The histological and histochemical investigation indicated that fluoride exposure at 50.00 mg/L may cause damage of internal organs. The decreased activity of cells can be observed by the increased pigment granules and decreased concentration of BMP-2. The digestive system, especially the liver, is the one of the most sensitive organs, which can be significantly effected by fluoride exposure. Moreover, the organs of the endocrine system, such as thyroid gland, can also be influenced by fluoride exposure.In conclusion, exposure to fluoride at a low concentration (< 5.00 mg/L) is beneficial to the development of the larva Bufo gargarizans. It helps the larvae increase their body weight and total length quickly, which leads the larvae start their metamorphism in advance. Moreover, high concentration (≥10.00 mg/L) of fluoride can act as enzymatic poisons by interrupting the enzymes activities, and lead to the disorder of the metabolic processes and even death. It is the first systemic research on the effects of fluoride on the larval development of amphibian at home. This paper is of momentous significance in the term of theory and practice at the monitoring of environment and protection of animals.