Effects of UVB radiation on the skin lipids of garter snakes

Anna VigelandDr. 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

• Males differentiated in part by the presence of squalene

more attractiveless attractive

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

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 = 0.00934p = 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

• 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

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 red-sided 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?