Avian eggs usually experience temperatures of 30 to 40°C during the incubation period, but eggs often cool to much lower temperatures. Hyperthermia is less common. Passerines do not show higher incubation temperatures than other orders that have been studied extensively. Field measurements of incubation temperatures are usually lower than the optimal temperatures for development found in laboratory studies. Some species regulate egg temperatures closely throughout incubation; but in at least one penguin species, mean egg temperature increases and ranges of egg temperature decrease through the incubation period. Both the optimal temperature for continuous exposure and the range of temperatures producing high survivorship differ among species. Species also differ in their responses to temperature exposures of limited duration. Thus, the use of a "physiological zero" applicable to all species is not warranted. Penguins have both a lower optimum and a broader range of acceptable incubation temperatures than do other species studied. Age, duration, and temperature of exposure significantly affect survivorship. Hyperthermia is evidently more injurious to the developing embryo than is hypothermia. Resistance to cold exposure is a heritable trait, but the genetics and physiology of the response(s) are not known. For older embryos, the physiological effects of hyperthermia are similar to those of adult birds in terms of the organ systems that are first to fail. An estimate of thermal tolerance for short exposures in most species studied is 16 to 41°C and, for exposures lasting several hours, 36 to 39°C.

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Yellow-bellied marmots (Marmota flaviventris) were studied at three sites in central Oregon. Juveniles substantially reduced their foraging activity when equivalent black-body temperatures exceeded their upper critical temperature. Inclusion of heat stress into estimates of environmental harshness drastically reduced the differences in available foraging time between high elevation and low elevation sites.

The use of gonopodial indices as potential indicators of endocrine disruption in the mosquitofish Gambusia holbrooki inhabiting south west Australian wetlands was investigated. A minimum of 50 mature males was collected from each of five water-bodies in the Swan Coastal Plain, Western Australia, in order to measure morphological features related to reproduction. A set of morphological measurements were used to derive the following indices: gonopodium length/standard body length, pre-anal length/standard body length, the index of elongation and the percentage of male fish with hooks on the distal end of the gonopodium. Indices of male mosquitofish collected from Jack Finney Lake, located in the Curtin University campus, suggest the presence of endocrine disrupting chemicals (EDCs) in this water-body, while those from Lake Kulinup suggest this is a site of concern. Indices of male fish from the Wagerup wetland, Lake Monger and Loch McNess indicate that fish inhabiting these wetlands are not affected by EDCs. This preliminary study suggests that EDCs may be present in a number of wetlands of the Swan Coastal Plain. Further study using EDC specific markers such as vitellogenin induction in male mosquitofish is required to confirm whether EDCs are present in these water-bodies.

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Hsp70 protein in three tissue types (gill, liver, and muscle) from black bream (Acanthopagrus butcheri) collected in a highly variable estuarine environment was investigated to determine which tissue provides better intersite discrimination. The usefulness of hsp70 expression to identify anthropogenic stress under field conditions was evaluated. Intersite differences were detected in hsp70 levels in gill and white muscle of black bream while liver showed no spatial difference. There was high interfish variability in hsp70 levels in each tissue group. A post hoc power analysis of the datasets for each tissue found that in black bream, white muscle provided the best discriminatory power to elucidate spatial variability. Only 11 fish per site are required to identify significant intersite differences in white muscle whereas for gill and liver tissues 14 and 21 fish per site, respectively, would be required. Because of high intertissue and interindividual variability, field measurement of hsp70 should be complemented by evidence of changes in other biomarkers of fish health.