Availability of water affects organ growth in prenatal and neonatal snapping turtles (Chelydra serpentina)

Abstract

We manipulated the amount of water that was available to prenatal and neonatal snapping turtles (Chelydra serpentina) in order to assess the impact of water on growth by different organs in these animals. Three treatments were used: (1) turtles that completed their incubation on a wet substrate, (2) turtles that completed their incubation on a dry substrate, and (3) turtles that spent a few days in water after completing incubation on a dry substrate. Turtles hatching on a dry substrate (treatment 2) were smaller than animals in the other two treatments (which did not differ in size), so data for mass of different organs were adjusted by ANCOVA to remove effects of body size. Scaled masses of liver, stomach, lungs, kidneys, and small intestine did not differ between turtles emerging in wet environments and those hatching in dry environments, but hearts of turtles hatching in dry settings were substantially larger than those of animals hatching in wet ones. Thus, the mass of most organs in turtles developing in wet and dry environments scaled to body size, whereas the heart was hypertrophied in embryos developing in dry environments. Turtles that spent a few days in water after hatching from eggs in dry environments grew rapidly in size, and the increase in body size was accompanied by disproportionately rapid growth in the liver, stomach, lungs, kidneys, and small intestine. The heart did not increase in size during this period, despite the substantial increase in body mass over that at hatching. The enlarged heart of turtles hatching on dry substrates may have been caused by a circulatory hypovolemia late in incubation; the rapid growth of organs other than the heart when these animals were placed in water may reflect a release from constraints on growth once circulatory volume was restored.