氟离子慢性暴露对中国林蛙蝌蚪生长发育的毒性效应研究

氟元素以不同的结合形式广泛存在于自然界中,适量氟的摄取有益于龋齿预防和骨骼发育,然而过量氟的摄取会对动物及人体健康造成危害。近年来,大量的人类活动导致水环境中氟含量持续升高。为探究水域氟污染对中国林蛙的毒性影响,本研究以中国林蛙(Rana chensinensis)胚胎为试验材料,对卵黄栓期(G12期)胚胎进行了0、0.7、4.2、19.4、42.8 mg·L~(-1)F-慢性水体暴露直至胚胎发育到变态高峰期(G42期)的研究。分别于暴露25 d和40 d后取样测定了蝌蚪全长、体长、体重和发育分期;此外,分析了F-慢性暴露对变态率、G42期蝌蚪的全长、体长、体重和后肢长以及G42期蝌蚪骨骼发育的影响。结果表明:暴露25 d时,4.2 mg·L~(-1)F-处理组促进了林蛙蝌蚪的生长发育,而42.8 mg·L~(-1)F-处理组显著抑制了蝌蚪的生长发育;暴露40 d时,19.4 mg·L~(-1)F-和42.8 mg·L~(-1)F-处理组蝌蚪的生长发育均受到显著抑制。持续进行慢性暴露78 d后,4.2 mg·L~(-1)F-处理组蝌蚪的变态率显著升高,而42.8 mg·L~(-1)F-处理组蝌蚪的变态率受到了显著抑制。此外,42.8 mg·L~(-1)F-处理组G42期蝌蚪形态指标(全长、体长和后肢长)以及骨骼发育均受到抑制。依据G42期中国林蛙蝌蚪的生长发育指标和变态率为观察指标,氟离子慢性暴露对中国林蛙蝌蚪的最低可观察效应浓度(LOEC)为0.7 mg·L~(-1)。研究表明,水环境中高浓度的氟污染会对中国林蛙蝌蚪的生长发育、变态和骨骼发育等造成潜在的不利影响,水体氟污染的生态毒性效应理应引起高度重视。

Chronic Effects of Fluoride Exposure on Growth and Development in Rana chensinensis Tadpoles

Fluoride is widely distributed in nature in many forms. Fluoride at suitable dose is beneficial to animal development, while excessive fluoride intake may cause the adverse effects on animals. Concentrations of fluoride in aquatic environments have increased dramatically due to anthropogenic activities in recent years. The aim of this study is to assess the toxic effects of fluoride exposure on Rana chensinensis tadpoles. The R. chensinensis embryos were exposed to fluoride at the concentrations of 0.7, 4.2, 19.4 and 42.8 mg·L-1 from Gosner stage 12 (G12) to metamorphic climax (G42). Total length, body length, body weight, and developmental stage of tadpoles were examined on day 25 and 40. Time to metamorphosis and the size at G42 of tadpoles were determined. Also, skeletal systems of tadpoles at G42 were investigated using double-staining methodology. The growth and development of tadpoles were significantly promoted at 4.2 mg·L-1 F-, but were significantly suppressed at 42.8 mg·L-1 F- on day 25. On day 40, the growth and development of tadpoles relative to controls were significantly inhibited at 19.4 and 42.8 mg·L-1 F-. In addition, significant metamorphic delay and a decrease in the size at G42 were found in the larvae exposed to 42.8 mg·L-1 F-. Moreover, the bone mineralization of tadpoles at G42 could be suppressed by 42.8 mg·L-1 F-. The lowest observed effect concentration (LOEC) of F- exposure based on the growth and development at G42 and percent metamorphosis of tadpoles was 0.7 mg·L-1. In conclusion, our results suggested that the high dose fluoride could inhibit growth and development, delay metamorphosis and suppress skeletal ossification in R. chensinensis tadpoles. More attention should be paid to fluoride pollution in aquatic ecosystems in future, because fluoride has a potential to cause adverse effects on aquatic animals.