Effect of population density on adrenal glands and reproductive organs of CFW mice

¹ Department of Zoology, Ohio University, Athens, Ohio

Young mice of the CFW albino strain were subjected to fixed population densities of 1, 4, 8 and 16 animals/cage after a 3-week period of isolation. After 1 week of such groupings, the animals were sacrificed, the adrenal glands, testes and seminal vesicles were weighed and histological preparations were made of the adrenal glands. The increased adrenal weights and decreased reproductive organ weights reported by Christian (Am. J. Physiol. 181: 477, 1955; 182: 292, 1955) did not occur in the group means of male populations. Increased relative adrenal weights (mg adrenal weight/gm body weight) did occur in wounded animals of these populations, however. Increased relative adrenal weights of males also occurred in populations containing 50% females. Increased adrenal weight was usually, but not consistently, associated with increased cortical width. Testes weights were unaffected by population density. Seminal vesicle weights declined with increasing population density. Crowding increased fertility in groups of 4 and 8, whereas, it impaired fertility in groups of 16.

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