Pam Clarkson

1
Effects of atrazine on thyroid hormone induction
of metamorphosis in the axolotl (Ambystoma
mexicanum)
Pam Clarkson
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ENDOCRINE DISRUPTION
ATRAZINE
-- Post application (Spring) runoff can be gt 20
ppb -- typical surface and groundwater
concentrations at other times during other times
of the year, 0.001 to 1.0 ppb -- 3 ppb EPA
standard for drinking water
Males exposed to 0.1 ppb have lowered
testosterone, elevated estrogen, and intersex
gonads
Xenopus laevis Hayes et al, 2002, PNAS
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Introduction

• Thyroid hormones induce metamorphosis in the
  axolotl
• We investigate affects of atrazine on
  TH-induction of metamorphosis in the axolotl
• We investigate affects of atrazine on growth

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Big Picture To begin characterization of gene
expression during salamander metamorphosis Hypothe
sis no variation in gene expression during
metamorphosis
For comparison to endocrine disrupted
metamorphosis
To correlate patterns of gene expression with
morphological, developmental, and life history
malformations during endocrine disruption
To identify loci that will be useful in field
diagnostics of normal and endocrine disrupted
metamorphosis
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paedomorphosis
metamorphosis
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Page et al., 2007
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Results Summary
- Effect of atrazine on growth - Confirm
standrard TH-induction - Effect of atrazine on
metamorphosis
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pre-TH mass (g)
post-TH length (mm SVL)
7
7
0
35
0
35
)
)
gill length (mm)
fin length (mm)
0
7
35
0
35
7
)
)
9
pre-TH mass (g)
post-TH length (mm SVL)
0
5
5
50
0
50
gill length (mm)
fin length (mm)
5
0
5
50
0
50
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ACKNOWLEDGMENTS Chris Beachy (MSU) Heather
Modrow (MSU) Leah Crites (MSU) Charles Crites
(MSU) Amanda Lafountain (MSU) Sharon Denks
(FBCC) Dwight Blackhawk (FBCC) Erica Goodbear
(FBCC) Janel Richter (MSU) Heather Modrow
(MSU) Claude Ouedraego (MSU) Karen Pocha-Melby
(MSU)
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Summation

• - Accelerated growth at intermediate atrazine
  dosage effect is corroborated in our lab in
  other experiments
• Axolotls undergo metamorphosis after
  TH-induction
• - Failed to find any effect of atrazine on
  metamorphosis