Sensitivity to Urea Fertilization in the Marsh frog (Pelophylax sp.): Survey of Development and Survival

A large proportion of the amphibian life cycle occurs in ponds, streams, and temporary pools that are often associated with agricultural areas receiving fertilizers. Therefore, some anuran species inhabiting such environments may be exposed to the toxic effects of fertilizers. Urea is one of the most widely used fertilizers in agricultural lands, but little data is known about its impact on the development and survival of amphibians. For this purpose, to evaluate the impact of urea fertilization on the eggs of Marsh frog (Pelophylax sp.) which distributed in north and northeast of Iran, we investigated survival rate, hatching time and hatching rate during embryonic period (Gosner≥۲۵). In this study, ۷۲۰ eggs of Marsh frog with a density of ۲۰ and a water volume of ۱۵۰۰ ml per container, in three replications at concentrations of ۰ (control), ۵۰, ۱۰۰, ۱۵۰, ۲۰۰, ۳۰۰, ۵۰۰, ۷۰۰, ۱۰۰۰, ۱۵۰۰, ۲۰۰۰ and ۳۰۰۰ mg/l, with an average temperature of ۲۴°C, conducted for ۲۴ days. The larvae hatched in the control and concentrations of ۵۰ to ۵۰۰ on day of ۶. The hatching rate in concentrations above ۵۰۰ was ۰%, but in the control and concentrations of ۵۰ to ۳۰۰ were ۱۰۰%, in concentration of ۵۰۰ was ۱۱.۶۶%±۲۰.۲۰. The survival rate ۷۲h after hatching period (hatching period ۱۰ days) in the control and concentrations of ۵۰ to ۱۵۰, ۲۰۰, ۳۰۰ and ۵۰۰ recorded ۱۰۰%, ۹۶.۶۶%±۲.۸۸, ۷۰.۳۳%±۲۲.۹۱ and ۱.۶۶%±۲.۸۸, respectively. Survival rates on the ۲۴ days in the control and concentrations of ۵۰, ۱۰۰, ۱۵۰, ۲۰۰, ۳۰۰ and ۵۰۰ recorded ۱۰۰%, ۱۰۰%, ۹۵%±۵.۰۰, ۹۰%±۵.۰۰, ۹۱.۶۶±۵.۷۷, ۶۱.۶۶±۱۴.۴۳ and ۰%, respectively. According to the results, concentrations above ۳۰۰ mg/l of urea fertilization greatly affected the survival of Marsh frog eggs. Therefore, these effects are important to consider in light of possible threats to the conservation status of many amphibian species.

کلیدواژه ها:

Global amphibians decline ، Anuran ، Embryonic period