effects of uvb radiation on the skin lipids of garter snakes anna vigeland dr. m. rockwell parker...
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Effects of UVB radiation on the skin lipids of garter snakes
Anna VigelandDr. M. Rockwell Parker
Dr. Robert T. Mason
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Study Species
Red-sided Garter Snake (Thamnophis sirtalis parietalis)
• Model organism
• Hibernate 8 months in large hibernacula
• Emerge by the thousands in late spring
• Breeding follows for a few weeks
• Courtship behavior mediated by pheromones produced in the skin
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Garter Snake Environment
• Most northerly living reptile
• Study snakes caught at dens in Manitoba
• Northern regions strongly subject to
environmental changes
• UVB radiation
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Skin Lipid Profile
• 18 long-chain saturated and monounsaturated methyl ketones in pheromone
• High ratios of unsaturated and high molecular weight methyl ketones are associated with large, healthy females
• Males differentiated in part by the presence of squalene
more attractiveless attractive
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Skin Lipid Profile
Gas chromatograph of a typical female pheromone sample
Saturated
Unsaturated
394 408 420
422
434436 492
478
450
464
506
448
462
476
490
504
518
532
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Objective
Methyl ketone ratios change during the summer
in the field but not in the lab
Why?
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Hypothesis
Ultraviolet radiation causes qualitative changes in
the skin lipid profiles of red-sided garter snakes
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Question 1
Does ultraviolet-B radiation have an effect on the
female sexual attractiveness pheromone?
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Methods
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UVB radiation on female pheromone samples
Full-spectrum light only Full-spectrum and UVB light
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**
*
*
**
*
* p < 0.05
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UVB exposure affects the ratios of pheromone samples
p = 0.00934p = 0.00934
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Question 2
Does ultraviolet-B radiation have the same effect on the female sexual attractiveness pheromone when
in mixture with other skin lipids?
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Methods
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Pheromone irradiated within neat solution
Full spectrum light only Full spectrum and UVB light
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Pheromone irradiated within neat solution
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• Two groups of snakes exposed to either full spectrum or full spectrum +UVB light
• Behavioral and physical changes examined after prolonged UV exposure
• Skin lipid analysis after exposure period
Live-animal exposure: overview
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Question 3
Does exposure to ultraviolet-B radiation have an effect on the behavior of red-sided garter snakes?
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Methods
Short-term: detection and/or avoidance of UVB light
• Cardboard tube test: % snakes seeking refuge in tubes
• Mylar filter test: % snakes situated under Mylar vs. acetate
Long-term: snake activity levels
• Observation and categorization of behaviors:
% snakes active, alert, or resting
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UVB radiation does not affect snake behavior
• No significant differences in number of snakes seeking refuge in cardboard tubes
• Equal numbers of snakes situated under Mylar filters as under acetate filters
• No significant differences in the activity levels between treatment groups or after the 15-day exposure period
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Question 4
What effects does daily exposure to ultraviolet-B radiation have on the neutral skin lipids of red-sided
garter snakes?
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Methods
• Skin lipid extraction by soaking in hexane
• Purification of female attractiveness pheromone and squalene by alumina column chromatography
• Analysis of pheromone concentrations by gas chromatography
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Daily UVB on live snake pheromone ratios
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Environmental Implications
• UVB radiation has an effect on the female attractiveness pheromone and its US:S ratio
• UVB radiation has been increasing, especially in polar latitudes, due to ozone depletion
• Increases in UVB could affect red-sided garter snake reproductive behavior
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Further Research
• Gas chromatography analysis of squalene concentrations
• Thin layer chromatography to test for major differences in other neutral skin lipids
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Acknowledgements
Funding provided by:• Howard Hughes Medical Institute
Special thanks to:• Dr. Robert T. Mason• Dr. M. Rockwell Parker• Mason Lab: Emily Uhrig, Mattie Squire, Chris Friesen, Ben
Burke• The Blaustein Lab
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Questions?