SOURCES OF MINERAL FOR GREEN IGUANAS (IGUANA-IGUANA) DEVELOPING IN EGGS EXPOSED TO DIFFERENT HYDRIC ENVIRONMENTS

Eggs of green iguanas (Iguana iguana) were incubated on wet and dry substrates at 31 C in an experiment assessing the relative importance of yolk and eggshell as sources of mineral for developing embryos. Eggs incubated on wet media weighed more late in incubation, and thus contained more water, than those exposed to dry media. The availability of water presumably affected the metabolism and growth of embryos. Hatchlings emerging from wet environments were larger, but had smaller residual yolks, than did hatchlings emerging from dry settings. Developing green iguanas obtained substantial calcium and small quantities of magnesium from the eggshell but used only the yolk as a source of phosphorus. Moreover, yolk-free carcasses of hatchlings from wet media contained more calcium and phosphorus than did carcasses of neonates from dry environments whereas the reverse was true for yolks. Thus, the amount of calcium recovered from the eggshell and the quantity of phosphorus absorbed from the yolk depended on the wetness of the environment. Our results indicate that patterns of mobilization and deposition of mineral in embryonic green iguanas are similar to those reported for embryos of other oviparous reptiles and confirm that hydric conditions encountered during incubation have profound effects on the physiology of embryos.