Pesticide Effects On Endocrine Function, Metabolism, And Thermoregulation In 13-Lined Ground Squirrels (Spermophilus Tridecemlineatus)


Jean A. Perry

Date of Graduation

Summer 2004


Master of Science in Biology



Committee Chair

Thomas Tomasi


Forty-one wild-caught 13-lined ground squirrels were chronically treated with non-lethal doses of the lipophilic pesticides atrazine and lindane prior to hibernation. These substances accumulate in body fat, and have been shown to interfere with normal thyroid function. Since proper thyroid function is necessary for normal metabolic and reproductive activity, it was hypothesized that these pesticides might disrupt these physiological processes. Animals were divided into 5 treatment groups (n=7-8): high lindane; low lindane; atrazine; low lindane/atrazine; and control, and hibernated individually in rodent cages kept in environmental chambers. Serum samples were collected from all animals before, during and after hibernation, and were used to measure thyroid and reproductive hormone concentrations via RIA. Resting metabolic rates at 30°C (RMR) were measured (as oxygen consumption rates) as well as metabolism at 8-25°C. Norepinephrine-induced nonshivering thermogenesis (NST) was measured in May and July. Body temperatures were measured with implanted transmitters. Although all thyroid hormones changed over time, none appeared to be affected by pesticide treatment. There was also no apparent treatment effect on any of the reproductive hormones. RMR was not affected by pesticide treatment, either before or after hibernation. NST values differed between treatments at both time periods: atrazine-treated animals had the lowest NST both times. The pesticide treatments didn't appear to affect body temperature (euthermic or torpid), heating/cooling rates, or duration of torpor bouts. With the possible exception of T₃ and NST, these pesticide treatments did not apparently impair thyroid or reproductive endocrinology.


pesticides, hibernation, endocrinology, atrazine, lindane, 13-lined ground squirrels

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© Jean A. Perry