Abstract
Paraquat (l,l'dimethyl-4, 4'-bipyridinium dichloride) has been used for a number of years in the United States and other countries as a herbicide in the control of broadleaf weeds and grasses in crop fields, orchards, and berry patches. It is utilized as both a pre-emergence and post-emergence herbicide. Paraquat may also be used in aquatic weed control in some countries but not in the United States. The recommended field application rate is usually 0.25 to 1.0 lb. paraquat cation/acre. The rate of application for aquatic weed control ranges from about 0.I to 2.0 parts per million (ppm), by weight in water (Newman 1970; Calderbank 1972). Little is known of the effects of paraquat on embryonic development in aquatic animals. Murry and Schreiweis (1977) have shown teratogenic malformations in embryos of Oryzias latipes and Paulov [1977) has carried out developmental and body protein studies of the effects of paraquat in Rana temporaria. The present study was conducted to observe lethal and gross teratogenic effects of a range of concentrations of paraquat on Rana pipiens embryos, including concentrations at the recommended aquatic field application rates.
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