Presentation Title

A Tale of Two Species: The Fathead Minnow and Northern Leopard Frog as Environmental Sentinels of the Elkhorn River

Advisor Information

Alan Kolok

Location

Milo Bail Student Center Dodge Room B

Presentation Type

Oral Presentation

Start Date

8-3-2013 2:15 PM

End Date

8-3-2013 2:30 PM

Abstract

Environmental sentinel organisms are commonly used to warn of toxic chemicals in the environment that may pose a significant health risk to wildlife. In the Midwest, runoff of pesticides is one source of toxic chemicals to agricultural watersheds that can affect both fish and frogs. The objective of this project was to assess the potential for adverse impacts in one such agricultural watershed, the Elkhorn River, on fathead minnows and northern leopard frogs. Frogs and fish were exposed for seven days to water collected during a pulse of agrichemical runoff in the Elkhorn River. Concentrations of pesticides were 1.6 to 281 times greater during the agrichemical pulse than during baseflow conditions following the pulse. The impact of pesticide exposure was assessed by measuring the mRNA expression of two estrogen responsive genes, vitellogenin (Vtg) and estrogen receptor-α (ERα), in liver tissues. Quantitative real-time PCR revealed that female fathead minnows exposed to Elkhorn River water were defeminized as indicated by the significant reductions in both Vtg and ERα, whereas female frogs were not. Conversely, exposed male northern leopard frogs were feminized as indicated by an increase in ERα mRNA, whereas male fish were not. The effects observed in the fish and frog sentinels provide warning signs that pesticides present in the Elkhorn River may significantly impair the reproductive health of exposed aquatic wildlife. The contrasting response between the two species suggests that effects observed in wildlife may not be consistent across taxa, highlighting the need for multiple species toxicity testing.

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Mar 8th, 2:15 PM Mar 8th, 2:30 PM

A Tale of Two Species: The Fathead Minnow and Northern Leopard Frog as Environmental Sentinels of the Elkhorn River

Milo Bail Student Center Dodge Room B

Environmental sentinel organisms are commonly used to warn of toxic chemicals in the environment that may pose a significant health risk to wildlife. In the Midwest, runoff of pesticides is one source of toxic chemicals to agricultural watersheds that can affect both fish and frogs. The objective of this project was to assess the potential for adverse impacts in one such agricultural watershed, the Elkhorn River, on fathead minnows and northern leopard frogs. Frogs and fish were exposed for seven days to water collected during a pulse of agrichemical runoff in the Elkhorn River. Concentrations of pesticides were 1.6 to 281 times greater during the agrichemical pulse than during baseflow conditions following the pulse. The impact of pesticide exposure was assessed by measuring the mRNA expression of two estrogen responsive genes, vitellogenin (Vtg) and estrogen receptor-α (ERα), in liver tissues. Quantitative real-time PCR revealed that female fathead minnows exposed to Elkhorn River water were defeminized as indicated by the significant reductions in both Vtg and ERα, whereas female frogs were not. Conversely, exposed male northern leopard frogs were feminized as indicated by an increase in ERα mRNA, whereas male fish were not. The effects observed in the fish and frog sentinels provide warning signs that pesticides present in the Elkhorn River may significantly impair the reproductive health of exposed aquatic wildlife. The contrasting response between the two species suggests that effects observed in wildlife may not be consistent across taxa, highlighting the need for multiple species toxicity testing.