Embryonic energetics in eggs of two species of Australian skink, Morethia boulengeri and Morethia adelaidensis

We used eggs of two species of Australian skinks, Morethia boulengeri and M . adelaidensis, to: (1) estimate the amount of energy consumed during embry onic development, and (2) to assess the assumption that lipid provides most of the energy to fuel development We estimated energy consumption in two w ays, using standard closed-system respirometry and by estimating energy los s during development by comparing energy contained in fresh eggs and in hat chlings. Eggs of M. boulengeri are smaller (173 mg +/- 4) than those of M. adelaidensis (217 mg +/- 8), as are the hatchlings (36.4 mg +/- 1.4, and 46 .2 mg +/- 1.7 dry mass, respectively). Incubation period is virtually ident ical (M. boulengeri: mean = 57.6, range 54-63; M. adelaidensis: mean = 57.7 , range 55-60; P = 0.942). The estimate of energy consumption during develo pment was similar using both methods for M. adelaidensis (46.8 +/- 0.8 ml O -2 or 898 +/- 15 J from respirometry and 807 +/- 57 J from bomb calorimetry ) and M. boulengeri (33.3 +/- 0.8 ml or 640 +/- 16 J and 576 +/- 36 J). Com mensurate with their larger size, embryos of M. adelaidensis consumed more energy during development than M. boulengeri, but there was no significant difference in the dry mass-specific metabolic cost for M. boulengeri (18.2 kJ g(-1) +/- 0.7 kJ) and M. adelaidensis (19.9 +/- 0.8 kJ g(-1), P = 0.1123 ). The respiratory exchange ratio was 0.76 +/- 0.01 in both species, indica ting that approximately equal quantities of energy are derived from protein and lipid during development.