Transcript The effects of ultraviolet radiation on the skin lipids of garter snakes

Effects of UVB radiation on the skin
lipids of garter snakes
Anna Vigeland
Dr. M. Rockwell Parker
Dr. Robert T. Mason
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
Garter Snake Environment
• Most northerly living reptile
• Study snakes caught at dens in Manitoba
• Northern regions strongly subject to
environmental changes
• UVB radiation
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
less attractive
more attractive
• Males differentiated in part by the presence of squalene
Skin Lipid Profile
Gas chromatograph of a typical female pheromone sample
504
Saturated
Unsaturated
478
532
450
518
476
506
490
448
422
394
408 420
436
434
464
462
492
Objective
Methyl ketone ratios change during the summer
in the field but not in the lab
Why?
Hypothesis
Ultraviolet radiation causes qualitative changes in
the skin lipid profiles of red-sided garter snakes
Question 1
Does ultraviolet-B radiation have an effect on the
female sexual attractiveness pheromone?
Methods
UVB radiation on female pheromone samples
Full-spectrum light only
Full-spectrum and UVB light
* p < 0.05
*
*
*
*
*
*
*
UVB exposure affects the ratios of pheromone samples
p = 0.00934
p = 0.00934
Question 2
Does ultraviolet-B radiation have the same effect on
the female sexual attractiveness pheromone when
in mixture with other skin lipids?
Methods
Pheromone irradiated within neat solution
Full spectrum light only
Full spectrum and UVB light
Pheromone irradiated within neat solution
Live-animal exposure: overview
• 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
Question 3
Does exposure to ultraviolet-B radiation have an
effect on the behavior of red-sided garter snakes?
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
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
Question 4
What effects does daily exposure to ultraviolet-B
radiation have on the neutral skin lipids of red-sided
garter snakes?
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
Daily UVB on live snake pheromone ratios
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 redsided garter snake reproductive
behavior
Further Research
• Gas chromatography analysis of squalene
concentrations
• Thin layer chromatography to test for major
differences in other neutral skin lipids
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
Questions?