Developmental Toxicity of Atrazine in the Species Danio rerio By: Christy Bates

1. Developmental Toxicity of Atrazine in the Species Danio rerioBy: Christy Bates • Results • No data available • Conclusions • In this experiment there were many complications. The problem in this experiment was the inability to collect the embryos once spawning had been completed. These organisms are known for eating their embryos, so the challenge was finding a way to deter them from being able to reach the embryos. The zebrafish were able to reach the embryos with the first breeding chamber due to the separator being too narrow. Then, when the marbles were put into the tank the zebrafish were able to move the marbles. Next, when the screen was placed on the bottom of the tank they were able to get through the screen. The last attempt, the use of modified breeding chambers out of 2 liter plastic bottles, has not be successful yet. This is due to the zebrafish not spawning at this time. • Therefore the collection of the embryos after spawning wasn’t successful. The toxicity effects that atrazine has on the development of zebrafish was not demonstrated due to the unsuccessful attempts of collecting the embryos. The research indicated that these organisms were model organisms due to the brief spawning cycles, the ease of spawning, and the amount of embryos during those spawning cycles. Unfortunately, my experience with zebrafish in the laboratory has not shown that these organisms are model organisms for research due to the difficulty in collecting the embryos before they have a chance to eat the embryos. • As stated earlier, animal studies have shown that atrazine can be harmful to organisms. Another concern is the potential harm that it may be causing humans. This herbicide is the most commonly used herbicide across the United States, with more than 66 million pounds applied to corn alone, so it is important to know the consequences of this use of this chemical. • Literature cited • Ton C, Lin Y, Willett C. 2006. Zebrafish as a model for developmental neurotoxicity testing. Birth Defects Research. 76:553-567 • Del Carmen Alvarez,M, Fuiman,L. 2005. Environmental levels of atrazine and its degradation products impair survival skills and growth of red drum larvae. Aquatic Toxicology. 74: 229-241 • Markovich M, Rizzuto N, Brown P. 2007. Diet affects spawning in Zebrafish. Zebrafish. 4(1): 69-74. • Weigand C, Krause E, Steinberg C, Pflugmacher S. 2001. Toxicokinetics of Atrazine in the embryos of the Zebrafish (Danio rerio). Ecotoxicology & Environmental Safety. 49: 199-205. • Suzawa M, Ingraham H. 2008. The herbicide Atrazine activates endocrine gene networks via non-steroidal NR5A nuclear receptors in fish and mammalian cells. PLoS ONE. 3(5): e2117. • Acknowledgements • Dr. Lustofin Advisor • Dr. Brown • Biology Department • Biology Capstone Class Introduction Atrazine is an herbicide used to control broadleaf and grassy weeds in many types of crops, including corn, soybean, and sugar cane. Atrazine is also found in water supplies due to its inability to bind to the soil. The EPA considers levels below 3 µg/L of atrazine in water to be safe for drinking (Wiegand et al., 2001, 199). Unfortunately, levels as high as 40 µg/L to 60 µg/L in drinking water supplies have been documented (del Carmen Alvarez et al.,2005, 230). Atrazine has been show in animal studies to cause developmental problems. For example, in frogs, male frogs are feminized ( Suzawa et al.,2008, e2117). In mouse studies, neurological and reproductive problems have been reported (Suzawa et al., 2008, e2117). Danio rerio, commonly knownaszebrafish, are model organisms for laboratory experiments. They are hearty and durable organisms. Their embryos are translucent, which makes evaluating malformations easier to examine, and also they can produce many embryos in one spawning (Ton et al., 2006, 554). Another key factor to using zebrafish is that their natural environment is water and this is where the concern about atrazine comes into question. If these organisms are being affected by atrazine, other organisms could be experiencing the same effects from atrazine being present in high levels. I hypothesized that higher levels of atrazine will cause developmental disruption to the embryos of zebrafish. Those malformations include caudal embryo morphology (Figure 2), hemorrhaging, ventricle swelling, brain necrosis, jaw malformations, and motility abnormalities (Ton et al., 2006, 556) Methods The first step in this experiment was spawning the zebrafish. Zebrafish were maintained in a 10 gallon aquarium at pH of 6.8 with water temperature of 25°C, and a 10 hour day, 14 hour night cycle. They were fed TetraMin flake food three times daily. This was as close to optimal spawning conditions as described by Markovich et al..(Markovich et al., 2007, 72). The second step in this experiment was collecting the embryos. (Figure 1) Many attempts were made to successfully obtain the embryos. The first attempt involved placement of the selected breeding fish into a standard breeder. The second attempt was the placement of marbles around the tank to be used as a substrate for the embryos during spawning. The third attempt was the addition of a screen to separate the fish from their embryos. The last attempt was the placement of the fish into 2 liter plastic soda bottles that were modified and used as breeding containers. http://www.fac.org.ar/scvc/llave/pediat/diaz/diazf9.jpg Figure 1 http://www.neuraldevelopment.com/content/supplementary/1749-8104-4-12-s1.jpeg Figure 2