Sodium provision and wild cottontail rabbits: morphological change in adrenal glands

A direct relationship exists between sodium (Na) nutrition and morphology of the mammalian adrenal cortex, but little research on the relationship between soil Na levels and herbivore populat Consequently, we assessed the effect of Na on wild cottontail rabbits (Sylvilagus floridanus) inhabi poor soils in southcentral Indiana by characterizing their adrenal mass and histology prior to, and provision of supplemental Na. Data and tissues were collected at annual (1985-87) hunter check stati during the 1987 breeding season at the Atterbury Fish and Wildlife Area. Nutrient supplements, consi of either deionized water (controls) or 150 meq aqueous NaCl, were delivered via dripper bottles to replicates of each treatment throughout the spring and summer of 1986-87. Additionally, NaCl was del via impregnated pegs through winter 1986 and spring 1987. Hypotheses tests relative to the 1985 harv served to evaluate adrenal morphology with respect to treatments prior to experimental manipulation. the 1985 pretreatment period there was no evidence (P [less than or equal to]0.99, n = 828) of extan morphology by treatment type. Following introduction of supplements, adrenal mass (mg/g body mass) declined uniformly across age (adult, juvenile) and sex classes among rabbits with access to ancilla (1986: P [less than or equal to]0.05, n = 422; 1987: P [less than or equal to]0.10, n = 456). Relati (P [less than or equal to]0.05) in response to Na provision. Although mass and cortical area decline cortical area of the zona glomerulosa, in which the hormone aldosterone is produced, did not additio decline, but did differ by sex. The marked response of the adrenal gland to Na provision suggests th Na poor environments, Na nutrition may be a valid management concern.