Changes in the adrenal glands and lymph nodes of the Uinta ground squirrel with respect to age, sex, and seasonal events


Category:  Wildlife Science
Linked Publication
Language: English
Author(s): R. Charles Larlham
Description: Adrenal glands and lymph nodes were taken from animals of a free-living population of Uinta ground squirrels (Spermophilus-"armatus). The objective was to measure the changes in the adrenal glands and lymph nodes as the animals responded to seasonal population events. It was found that the adult females had smaller adrenal glands early in the season than adult males, but that there, was no early season difference in the adrenal weights of yearling males and females. Perhaps early season androgen production in the adult males elevated adrenal weights as it has been reported to do in the hamster. A lack of testi-cular development in yearling males may explain the lack of difference between yearling male and female adrenal gland weights early in the season. Adult female adrenal weights increased more rapidly through the season than those of adult males. The adrenal weights of yearlings of both sexes increased more rapidly during the first 47 days of the season than adrenal weights of the adults of both sexes. Most of this more rapid increase was probably due to physical maturation of the yearlings during this period. Lymph nodes were found to be a less reliable indicator of response to population and environmental pressures. This was evidently due to adrenocorticosteroids and sex hormones acting directly upon the lymph nodes, at times in opposition to each other, and to age and sex varia-tion in response to disease.