Chemical preservation of plants and insects in natural resins

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Abstract
In Syrian hamsters, exposure to short photoperiods or constant darkness induces a decrease in gonadotrophin secretion and gonadal regression. After 10 to 12 weeks, animals undergo spontaneous gonadal reactivation, gonadotrophin concentrations rise, and in males, testes size increases and spermatogenesis resumes. Thetau mutation shortens the period of circadian wheel–running activity by 4 h in the homozygote. Here, we examine the impact of this mutation on the reproductive response to photoperiod change. Seventeen adulttau mutant and nine adult wild–type males were housed in complete darkness for 25 weeks and testes size determined at weekly intervals. Gonadal regression and subsequent recrudescence occurred in both groups of animals. Regression occurred more rapidly intau mutants, with a nadir significantly earlier than wild–types but after a similar number of circadian cycles. Rates of testicular recrudescence were similar in both groups. Our data suggest that an acceleration of the circadian period increases the rate of reproductive inhibition in animals exposed to inhibitory photoperiods. Once initiated, the rate of spontaneous reactivation may be independent of the circadian axis.