Total body water and water turnover rates in the estuarine diamondback terrapin (Malaclemys terrapin) during the transition from dormancy to activity

Abstract

Abstract Water and salt concentrations in an animal’s body fluids can fluctuate with changing environmental conditions, posing osmoregulatory challenges that require behavioral and physiological adjustments. The purpose of this study was to investigate body water dynamics in the estuarine diamondback terrapin (Malaclemys terrapin), a species that undergoes seasonal dormancy in salt marsh habitats. We conducted a field study to determine the total body water (TBW%), water turnover rate (WTR), and daily water flux (DWF) of female terrapins in southeastern North Carolina pre- and post-emergence from winter dormancy. Terrapins were injected with [2H]deuterium on two occasions and washout of the isotope was monitored by taking successive blood samples during the period of transition from dormancy to activity. The WTR and DWF of ‘dormant’ terrapins were significantly lower than those of ‘active’ terrapins (WTR’dormant’= 49.70 ± 15.94 ml day-1, WTR’active’ = 100.20 ± 20.36 ml day-1, DWF’dormant’= 10.52 ± 2.92 %TBW day-1, DWF’active’ = 21.84 ± 7.30 %TBW day-1). There was no significant difference in TBW% between ‘dormant’ and ‘active’ terrapins (75.05 ± 6.19% and 74.54 ± 4.36%, respectively). Results from this field study provides insight into the terrapin’s ability to maintain osmotic homeostasis while experiencing shifts in behavioral and environmental conditions.