Reproductive investment compromises maternal health in three species of freshwater turtle

Life-history theory predicts that a trade-off in the allocation of resources between different physiological systems exists because resources are finite. As a result, females investing heavily in reproduction may compromise their future health. We used hematology, serum biochemistry, mass, and morphometric measurements as indicators of physiological health state to investigate whether reproductive investment altered subsequent maternal health in three Australian freshwater turtles: the oblong turtle (Chelodina oblonga; n = 12), the Macquarie turtle (Emydura macquarii; n = 9), and the eastern long-necked turtle (Chelodina longicollis; n = 8). Maternal health was impaired in turtles that produced larger and heavier eggs and clutches. In C. oblonga and E. macquarii, increased reproductive investment generally resulted in negative changes to the hematology and serum biochemistry profile of maternal blood. Generally, increases in heterophil/lymphocyte ratio, aspartate transaminase, creatine kinase, calcium/phosphorus ratio, and albumin/globulin ratio were observed following reproduction, in addition to a decrease in glucose and total protein. These findings agree with the physiological constraint hypothesis and highlight the connection between life-history evolution and animal physiology by documenting, for the first time, how measures of physiological health state relate to reproductive investment in Australian freshwater turtles. Additionally, our findings suggest that body condition, a readily used morphological biomarker, is a poor predictor of health in turtles. Our results emphasize the need to investigate how maternal health is influenced by the reproductive process in different species.