Abstract
In this study, atrazine has been shown to act as a potent endocrine disruptor in amphibians either alone or in combination with nitrate under stable laboratory conditions, causing altered gonadal development at the sub-lethal concentrations. A control group and three treatments were tested; atrazine, nitrate, atrazine- nitrate treatments with doses of 300 μg/L, 200 mg/L and their combination, respectively. Atrazine exhibited increase the presence of testicular oocytes TOs in most treated specimens; furthermore, the sizes of seminiferous tubules were decreased compared to control group. Conversely no intersex individuals were detected in the nitrate treatment alone. The combined effects of nitrate and atrazine were not additive or synergistic but were similar to the effects of atrazine in raising the percentage of intersex but with increasing the size of testicular oocyte compared to atrazine alone. On the other hand, the control group in the present study did not contain the rudimentary testicular oocytes and showed normal structures. These gonadal abnormalities may reduce reproductive success and could be a major factor behind amphibian declines. Also, these negative impacts may be a bioindicator alarming the ecosystem disrupting caused by the uncontrolled apply of these chemicals in agriculture.
Highlights
Amphibians are important ecological components of both wet and dry lands [1, 2]
Testicular oocytes were observed in most individuals treated with atrazine (Figures 1 d&1 e), atrazine showed decrease in the size of seminiferous tubules (Figure 1 e) compared to with control group (Figure 1 c)
This study assessed the potential influence of atrazine and nitrate exposure on Sclerophrys regularis toads reared under controlled laboratory conditions, by investing possible effects of such contaminants on gonadal development on exposure to sublethal doses, that seemed to be relevant to environmental concentrations at many areas worldwide. 300 μg/l atrazine, 200 mg/l nitrate and combined dose treated animals experienced significantly development of testicular oocytes (TOs) in gonads and decreased the size of testes
Summary
Amphibians are important ecological components of both wet and dry lands [1, 2]. Among vertebrates they are distinctive in many ways and contribute in many ecosystem services, so they have an important ecological and human role. The present study will intensely focus on the atrazine and nitrate as the most common herbicide and fertilizer, respectively addressing their role in amphibian decline in general and their effect on Amietophrynus regularis in particular which is a common Egyptian toad using agricultural fields and other disturbed areas and could be exposed to contaminants through several different routes and across all life stages. One of the most widely used pesticides in the world, can be transported more than 1,000 km from the point of application via rainfall [5] even in
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