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Rigid-shelled eggs of the broad-shelled river turtle Chelodina expansa were incubated at 28 degrees C in wet (-100 kPa), intermediate (-350 kPa) and dry (-750 kPa) conditions. Incubation period was influenced by clutch of origin, but was independent of incubation water potential. Rates of water gained from the environment and pre-pipping egg mass were influenced by incubation water potential -- eggs incubating at higher (less negative) water potentials absorbing more water from their environment. Hatchlings from wet conditions had greater mass but a smaller amount of residual yolk than hatchlings from dry conditions and it is suggested that the amount of yolk converted to tissue is influenced by the amount of water absorbed by the egg during incubation. Water content of yolk-free hatchlings from the -100-kPa treatment was greater than those from the -350-kPa and -750-kPa treatments, but the water content of residual yolks was similar across all hydric conditions.

Eggs of two small Australian lizards, Lampropholis guichenoti and Bassiana duperreyi, were incubated to hatching at 25 degrees C and 30 degrees C. Incubation periods were significantly longer at 25 degrees C in both species, and temperature had a greater effect on the incubation period of B. duperreyi (41.0 days at 25 degrees C; 23.1 days at 30 degrees C) than L. guichenoti (40.1 days at 25 degrees C; 27.7 days at 30 degrees C). Patterns of oxygen consumption were similar in both species at both temperatures, being sigmoidal in shape with a fall in the rate of oxygen consumption just prior to hatching. The higher incubation temperature resulted in higher peak and higher prehatch rates of oxygen consumption in both species. Total amount of oxygen consumed during incubation was independent of temperature in B. duperreyi, in which approximately 50 ml oxygen was consumed at both temperatures, but eggs of L. guichenoti incubated at 30 degrees C consumed significantly more (32.6 ml) than eggs incubated at 25 degrees C (28.5 ml). Hatchling mass was unaffected by either incubation temperature or the amount of water absorbed by eggs during incubation in both species. The energetic production cost of hatchling B. duperreyi (3.52 kJ x g(-1)) was independent of incubation temperature, whereas in L. guichenoti the production cost was greater at 30 degrees C (4.00 kJ x g(-1)) than at 25 degrees C (3.47 kJ g(-1)). Snout-vent lengths and mass of hatchlings were unaffected by incubation temperature in both species, but hatchling B. duperreyi incubated at 30 degrees C had longer tails (29.3 mm) than those from eggs incubated at 25 degrees C (26.2 mm). These results indicate that incubation temperature can affect the quality of hatchling lizards in terms of embryonic energy consumption and hatchling morphology.

Incubation temperature and the amount of water taken up by eggs from the substrate during incubation affects hatchling size and morphology in many oviparous reptiles. The Brisbane river turtle Emydura signata lays hard-shelled eggs and hatchling mass was unaffected by the amount of water gained or lost during incubation. Constant temperature incubation of eggs at 24 degrees C, 26 degrees C, 28 degrees C and 31 degrees C had no effect on hatchling mass, yolk-free hatchling mass, residual yolk mass, carapace length, carapace width, plastron length or plastron width. However, hatchlings incubated at 26 degrees C and 28 degrees C had wider heads than hatchlings incubated at 24 degrees C and 31 degrees C. Incubation period varied inversely with incubation temperature, while the rate of increase in oxygen consumption during the first part of incubation and the peak rate of oxygen consumption varied directly with incubation temperature. The total amount of oxygen consumed during development and hatchling production cost was significantly greater at 24 degrees C than at 26 degrees C, 28 degrees C and 31 degrees C. Hatchling mass and dimensions and total embryonic energy expenditure was directly proportional to initial egg mass.