Temporal, population, and sexual variation in hematocrit of free-living desert tortoises: correlational tests of causal hypotheses

摘要: Hematocrit (packed cell volume, PCV) varies seasonally in some vertebrates and often differs between the sexes among conspecific populations. Such variation PCV may reflect nutritional health, requirements for oxygen transport (metabolic rate), or hydration. The relative importance of these influences was tested with serial measurements two Mojave Desert populations desert tortoise (Gopherus agassizii) over activity seasons, during a period large seasonal differences availability food water. varied widely (range = 14–40, CV 20%), reflecting populations, sexes, years, time within years. Causal hypotheses were by correlating physiological indicators health (blood urea nitrogen), (field metabolic hydration (length-relative mass, water-influx rate, urine osmolality, plasma sodium, osmolality). Results indicated dominant inf...