Longer Incubation Periods are Energetically Costly for Turtle Embryos

Aims: To test the hypothesis that similar sized turtle eggs with longer incubation periods have a greater energetic cost of producing a hatchling compared with eggs that have a shorter incubation period.
Study Design: Eggs of the Eastern snake-neck turtle (Chelodina longicollis) were incubated at 26ºC and their oxygen consumption measured throughout incubation and these data compared to that from eggs of the Brisbane river turtle (Emydura macquarii) incubated at 26ºC.
Place and Duration of Study: The University of Queensland St Lucia Campus, November 2009 - February 2010.
Methodology: Eggs were collected and incubated at 26ºC and their rate of oxygen measured at regular intervals throughout incubation. Total energy expended during incubation was calculated by integrating the area under the rate of oxygen consumption versus time curve.
Results: Incubation period of C. longicollis eggs (83.1±0.5 d, N=12) and hatchling production cost (8.94±0.52 kJ/g, N=12, dry yolk-free mass basis) were significantly greater (P<0.001 and P=0.008 respectively) than the incubation period (61.8±0.3 d, N=11) and hatchling production cost (7.33±0.11 kJ/g, N=11) of E. macquarii eggs. These findings are consistent with the hypothesis that longer incubation periods incur a greater energetic cost because embryo tissue has to be maintained for a longer period of time and results in a greater amount of energy spent on maintaining the embryo.