1. The Harderian Gland Revealed:
Regeneration and Recovery of Chemosensory Function in Red-Sided Garter Snakes
Christina Lackey
Mentor: Dr. Robert Mason
HHMI – Oregon State University
University Honors College
Summer 2008

2. The Harderian Gland (HG)
First described in 1694 by Jacob Harder
Present in most terrestrial vertebrates
Secretes a wide range of products
Seldom described; function is poorly understood

3. The Harderian Gland in Red-sided Garter Snakes
The vomeronasal organ (VNO) functions in detecting nonvolatile chemical cues essential to mating and feeding.
The HG produces proteins that allow these chemicals to dissolve in the fluid filling the VNO.
-tongue-flicking
-mating  hunting

4. Seasonality
Feeding
Dormancy
Mating

5. Previous Research: Function
Snakes with their HGs removed did not recognize sex pheromones.
As a pilot to this study, they were also shown to be unresponsive to prey cues.

6. Previous Research: Regeneration
Snakes fed by using visual cues, then unexpectedly switched back to using chemical cues.
It was found that the HGs had grown back partially.

7. Hypotheses
Secretions from the Harderian gland are essential for the function of the vomeronasal organ in detecting prey.
The Harderian gland regenerates when removed.

8. Prediction
When the Harderian gland is removed, red-sided garter snakes will lose their ability to track prey using vomeronasal cues. As the gland regenerates, their tracking ability will return.

9. My Research
My goal was to repeat the initial experiment with a larger sample size (n = 70) and more controls.

10. My Research: Procedure
Half the snakes had their Harderian glands removed (Hdx), and half underwent surgery without Harderianectomy, as a control group (Sham).
The snakes were tested for trailing ability in ten-day intervals.
-describe setup, order of testing (T1-5)

11. My Research: Y-Mazes Trailing behavior was assessed using Y-mazes.
A worm’s trail was placed down the main arm and one of the secondary arms.
A snake’s ability to trail prey was determined based on the arm it chose, and also the amount of trailing behavior it exhibited.
-describe assessment of trailing behavior
-quantification of behavior

12. Trailing Behavior
Detection of a chemical cue is marked by distinctive trailing behavior.
The snake exhibits “chin-pressing” along the surface that contains the trail.

13. My Research: Data
After 80 days, all groups maintain a high level of trailing behavior.
This data does not support my first hypothesis.
Because HG function cannot be determined by behavior, tracking its regeneration becomes more difficult.
-use graph

14. Future Research
The data from this experiment alone suggest that the HG does not play as important a role in the detection of prey cues by the VNO as was predicted.
However, paired with the data from the pilot study, it suggests that the HG is involved in the process of the snakes’ switching from mating behavior to feeding behavior.

15. Future Research
Though the regeneration of the glands could not be tracked by behavioral observation, histological analysis will be used to address that hypothesis.

16. Acknowledgements My mentor, Dr. Robert Mason
Chris Friesen, who trained me and provided guidance
Kevin Ahern and the HHMI program
URISC
University Honors College
Everyone I worked with this summer: Rocky Parker, Amelia Kerns, Emily Uhrig, Dan Preston, and Elliot Finn