The effect of rearing temperature on development, body size, energetics and fecundity of the diamondback moth

Temperature is arguably the most important abiotic factor influencing the life history of ectotherms. It limits survival and affects all physiological and metabolic processes, including energy and nutrient procurement and processing, development and growth rates, locomotion ability and ultimately reproductive success. However, the influence of temperature on the energetic cost of development has not been thoroughly investigated. We show that in the diamondback moth [Plutella xylostella L. (Lepidoptera: Plutellidae)] rearing temperature (range 10-30°C) affected growth and development rates, the energetic cost of development and fecundity. Rearing at lower temperatures increased development times and slowed growth rate, but resulted in larger adult mass. Fecundity was lowest at 10°C, highest at 15°C and intermediate at temperatures of 20°C and above. At a given rearing temperature fecundity was correlated with pupal mass and most eggs were laid on the first day of oviposition, there was no correlation between total eggs laid and adult longevity. The highest production cost was incurred at 10°C; this decreased with increasing temperature, was minimized in the range 20-25°C, and then increased again at 30°C. These minimized production costs occurred at temperatures close to the intrinsic optimum temperature for this species and may reflect the rearing temperature for optimal fitness. Thus at sub-optimal temperatures greater food resources are required during the development period. Predicted increased temperatures at the margins of the current core distribution of P. xylostella could ameliorate current seasonal effects on fecundity, thereby increasing the probability of winter survival leading to more resilient range expansion and an increased probability of pest outbreaks.

Incubation of rigid-shelled turtle eggs: do hydric conditions matter?

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.

Development of the pulmonary surfactant system in the green sea turtle, Chelonia mydas

This study describes the developmental changes in pulmonary surfactant (PS) lipids throughout incubation in the sea turtle, Chelonia mydas. Total phospholipid (PL), disaturated phospholipid (DSP) and cholesterol (Chol) harvested from lung washings increased with advancing incubation, where secretion was maximal at pipping, coincident with the onset of pulmonary ventilation. The DSP/PL ratio increased, whereas the Chol/PL and the Chol/DSP ratio declined throughout development. The phospholipids, therefore, are independently regulated from Chol and their development matches that of mammals. To explore whether hypoxia could elicit an effect on the development of the PS system, embryos were exposed to a chronic dose of 17% O2 for the final approximately 40% of incubation. Hypoxia did not affect incubation time, absolute, nor relative abundance of the surfactant lipids, demonstrating that the development of the system is robust and that embryonic development continues unabated under mild hypoxia. Hypoxia-incubated hatchlings had lighter wet lung weights than those from normoxia, inferring that mild hypoxia facilitates lung clearance in this species.

How incubation temperature influences the physiology and growth of embryonic lizards

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.

Effects of incubation temperature on the energetics of embryonic development and hatchling morphology in the Brisbane river turtle Emydura signata

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.

Incubation of turtle eggs at different temperatures: do embryos compensate for temperature during development?

Freshwater turtle eggs are normally subjected to fluctuations in incubation temperature during natural incubation. Because of this, developing embryos may make physiological adjustments to growth and metabolism in response to incubation at different temperatures. I tested this hypothesis by incubating eggs of the Brisbane river turtle Emydura signata under four different temperature regimes, constant temperatures of 24 degrees C and 31 degrees C throughout incubation, and two swapped-temperature treatments where incubation temperature was changed approximately halfway through incubation. Incubation at 31 degrees C took 42 d, and incubation at 24 degrees C took 78 d, with intermediate incubation periods for the swapped-temperature treatments. Hatchling mass, hatchling size, and total oxygen consumed during development were similar for all incubation regimes. The pattern of oxygen consumption during the last phase of incubation as reflected by rate of increase of oxygen consumption, peak oxygen consumption, and fall in oxygen consumption before hatching was determined solely by the incubation temperature during the last phase of incubation; that is, incubation temperature during the first phase of incubation had no influence on these factors. Thus there is no evidence of temperature compensation in growth or development during embryonic development of E. signata eggs.

Hemoglobin function in a skin-breathing aquatic salamander, Desmognathus quadramaculatus

Adult black-bellied salamanders (Desmognathus quadramaculatus) were maintained in humidified gas at 12 degrees C. Hypoxic salamanders were exposed to 8.1-9.6% O2 for 10-11 days; normoxic animals were maintained in air (20.9% O2). Hypoxia acclimation had no effect on blood O2 affinity, O2 equilibrium curve shape or CO2 Bohr effect. At pH 7.7, P50 values for hypoxic and normoxic salamanders were 28.2 +/- 0.4 and 28.6 +/- 0.8 Torr, respectively. Hill plots were curvilinear for both treatments; Hill's n increased from values of 2.1-2.2 below 40% saturation (S) to 2.6 above 50% S. CO2 Bohr slopes (delta log P50/delta pH) were -0.19 +/- 0.01 and -0.23 +/- 0.02 for hypoxic and normoxic animals, respectively. Resting MO2 for a separate group of normoxic salamanders fell into two categories; low MO2 (1.46 +/- 0.16 mumol.g-1.h-1) and high MO2 (3.51 +/- 0.52) animals. Exposures to 5 and 25% CO had no effect on MO2 of low metabolism Desmognathus, but reduced MO2 of high metabolism animals to levels similar to the low MO2 group. Hb-O2 binding results suggest that D. quadramaculatus blood is ideally suited for respiratory O2 exchange during normoxic activity. While submerged and inactive, hypoxic boundary layers surround the skin-breather. Contributions of Hb during hypoxic inactivity may be to augment O2 content and increase blood buffering capacity.

Home Range and Hatching Success of Malleefowl, Leipoa-Ocellata Gould (Megapodiidae), in Murray Mallee Near Renmark, Sa

The home range of malleefowl in low-rainfall Murray mallee was approximately 4 km2, but home ranges of birds from different mounds overlapped to a considerable degree, resulting in an overall breeding density of 1.1 pairs per square kilometre. Mean clutch size (�95% CI) was 13.8 � 4.1, mean egg mass (�95% CI) 168�2 g; and 79.2% of eggs hatched successfully. No eggs were taken by foxes, but four out of six radio-tagged adults were eaten by foxes. These results differ from those of Frith, who studied malleefowl in high-rainfall mallee near Griffith, N.S.W. I suggest that differences in bird density and fecundity are related to vegetation differences, and that the difference in egg predation is related to differences in the way tkie incubation mounds at the two sites were maintained.

Water Flux in Malleefowl, Leipoa-Ocellata Gould (Megapodiidae)

Water efflux of captive and free-ranging malleefowl Leiopa ocellata (body mass 2.0 kg) was monitored over a complete annual cycle. Water efflux in captive adult birds remained relatively constant throughout the study period and averaged 26.3 ml. kg-'.d-', which is 30% of the predicted rate based on allometric criteria. Water efflux of free-ranging birds was higher and more variable than in captive birds and averaged 49.0 ml. kg-'.d-', 56% of the predicted rate. The low water efflux rates of malleefowl indicate that this species is well adapted to an arid environment. Multiple regression analysis failed to find a significant relationship between rainfall or mean air temperature and water efflux rate in free-ranging birds. An examination of the literature on avian water flux indicated that rates obtained from studies on captive birds are lower than those obtained from free-ranging birds; it is suggested that allometric analysis should take this factor into account. Two allometric equations are presented, one for captive birds, the other for free-ranging birds.