Pesticides Atrazine And Malathion Affect The Quality Of Frog Eggs And Cause Lower Fertilization Rate
Authors:Guihua Jing, Jessica Lee
Mentor:Junjun Liu, Associate Professor of Biological Sciences, California State Polytechnic University Pomona
Amphibians are considered to be indicator species for environmental health due to their highly permeable skin that makes them vulnerable to environmental contaminants. If their populations decline, it is likely that the quality of the habitat in which they live is affected. Amphibian populations have been declining dramatically worldwide since the 1980s. Many factors contribute to the decline, and accumulating evidence has suggested that the widely use of pesticides is one of the major reasons.
There are two immediate causes of amphibian population declines: death and reproductive failure. While much attention has been given to the cause on death, fewer studies have examined the decline as a result of impaired reproduction. The early reproductive stages are particularly susceptible to environment, and hence, any changes in environment will have a profound impact on amphibian population. Previous studies have shown that certain pesticides could cause decreased hatching success and developmental defects. We hypothesized that pesticides atrazine and malathion, two widely used pesticides in California, affect frog early development.
Xenopus laevis (African clawed frogs) was used as a model system. We treated oocytes that were surgically removed from frogs with atrazine and malathion and the maturation was induced by progesterone. To examine the fertilization rate, frog eggs and sperms were mixed in the presence of the pesticides, and cell division was monitored. Results showed that both atrazine and malathion impaired the quality of oocytes and eggs, including abnormal morphology, early maturation, poor quality eggs and lower fertilization rate. These effects were concentration dependent. A mixture of pesticides resulted in more significant effects, suggesting a more severe impact on amphibian population in areas that multiple pesticides were used.