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Embryonic Energetics in Eggs of Two Species of Australian Skink, Morethia boulengeri and Morethia adelaidensis

Michael B. Thompson and Kylie J. Russell
Journal of Herpetology
Vol. 33, No. 2 (Jun., 1999), pp. 291-297
DOI: 10.2307/1565726
Stable URL: http://www.jstor.org/stable/1565726
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Embryonic Energetics in Eggs of Two Species of Australian Skink, Morethia boulengeri and Morethia adelaidensis
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Abstract

We used eggs of two species of Australian skinks, Morethia boulengeri and M. adelaidensis, to: (1) estimate the amount of energy consumed during embryonic development, and (2) to assess the assumption that lipid provides most of the energy to fuel development. We estimated energy consumption in two ways, using standard closed-system respirometry and by estimating energy loss during development by comparing energy contained in fresh eggs and in hatchlings. 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 identical (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 development was similar using both methods for M. adelaidensis (46.8 ± 0.8 ml O2 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). Commensurate 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, indicating that approximately equal quantities of energy are derived from protein and lipid during development.

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