Title

Geographic Variation of Freeze Tolerance in the Pacific Chorus frog, Pseudacris regilla

Presenter Information

Sara Healas

Document Type

Oral Presentation

Location

SURC 271

Start Date

17-5-2012

End Date

17-5-2012

Abstract

This study is comparing the physiological responses to freezing of Pacific Chorus frogs from a coastal (Mill Creek) site, a central inland (Ellensburg) site, and a high-elevation site on Snoqualmie Pass. Pacific Chorus frogs have an amazing ability to freeze solid during the winter months. They are able to do this because they store massive amounts of glycogen that they break into glucose. Glucose is used for (1) to protect the cells during freezing and (2) to support general metabolism throughout the entire winter. The hypotheses are (1) where frogs would experience colder winters with less snow pack those frogs would produce more glucose and survive freezing to lower temperatures and (2) where frogs would experience longer winters, those frogs will produce more liver glycogen. We collected frogs in the spring from the Mill Creek, Ellensburg, and Snoqualmie Pass areas and housed them until the fall when they had developed their cold tolerance. They were then moved inside to an incubator set at 2°C. In January, the frogs were frozen in a cooling bath down to -2.5°C. Once frozen, the frogs were dissected and liver and thigh were extracted and frozen. Each tissue was later homogenized in acid and then neutralized with a base to extract the glucose and glycogen for measurement. The glucose and glycogen solutions were mixed with a color reagent which forms a colored product in the presence of glucose which was measured with a spectrophotometer. Results from the past three year’s experiments will be presented.

Faculty Mentor(s)

Jason Irwin

Additional Mentoring Department

Biological Sciences

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May 17th, 2:10 PM May 17th, 2:30 PM

Geographic Variation of Freeze Tolerance in the Pacific Chorus frog, Pseudacris regilla

SURC 271

This study is comparing the physiological responses to freezing of Pacific Chorus frogs from a coastal (Mill Creek) site, a central inland (Ellensburg) site, and a high-elevation site on Snoqualmie Pass. Pacific Chorus frogs have an amazing ability to freeze solid during the winter months. They are able to do this because they store massive amounts of glycogen that they break into glucose. Glucose is used for (1) to protect the cells during freezing and (2) to support general metabolism throughout the entire winter. The hypotheses are (1) where frogs would experience colder winters with less snow pack those frogs would produce more glucose and survive freezing to lower temperatures and (2) where frogs would experience longer winters, those frogs will produce more liver glycogen. We collected frogs in the spring from the Mill Creek, Ellensburg, and Snoqualmie Pass areas and housed them until the fall when they had developed their cold tolerance. They were then moved inside to an incubator set at 2°C. In January, the frogs were frozen in a cooling bath down to -2.5°C. Once frozen, the frogs were dissected and liver and thigh were extracted and frozen. Each tissue was later homogenized in acid and then neutralized with a base to extract the glucose and glycogen for measurement. The glucose and glycogen solutions were mixed with a color reagent which forms a colored product in the presence of glucose which was measured with a spectrophotometer. Results from the past three year’s experiments will be presented.