P3.21 Friday, Jan. 6 Hematological development in young arctic ground squirrels: a model for natural resistance to iron deficiency? ROBBINS, K.A.*; SHERO, M.R.; STEVENSON, T.; DUDDLESTON, K.; BUCK, C.L.; BURNS, J.M.; Univ. of N. Carolina, Wilmington; Univ. of Alaska, Anchorage; Univ. of Alaska, Anchorage; Univ. of Alaska, Anchorage; Univ. of Alaska, Anchorage; Univ. of Alaska, Anchorage firstname.lastname@example.org
In many mammals, postnatal development is accompanied by an anemia that persists until after independent foraging begins. This “physiological anemia of infancy” is attributed to rapid growth and expansion of heme stores during a period when iron intake rates are low. Since anemia and iron deficiency (ID) negatively impact development and performance, adaptations that reduce their magnitude or persistence may offer selective advantages. In Alaska, arctic ground squirrel (AGS; Urocitellus parryii) pups must mature rapidly during the short summer active season in order to prepare for their long overwinter hibernation. We therefore hypothesized that AGS pups would not suffer from developmental anemia. To test this hypothesis, we measured the blood and iron stores of 70 pups at 2 week intervals from birth until hibernation, and compared values to adult females. Pups grew rapidly across the entire period (11 g/d). However, while nursing and weaned pups had significantly (p < 0.05) lower hematological parameters (HCT, Hb, MCHC) than adults, anemia did not develop; rather all variables increased postweaning and reached adult values by the time pups were 2 months old. The increase in circulating heme stores was accompanied by significant new RBC production (reticulocytes). Liver iron stores declined even after pups began feeding; two month old pups had stores <50% those of adults. Together these findings suggest that endogenous and ingested iron is preferentially allocated toward rapid development, but that the apparent resistance to ID is only possible due to significant losses of iron reserves. Therefore, foraging on a nutritionally adequate diet once weaned is likely critical for proper growth and survival.