Embryonic Developmental Patterns and Energy Expenditure Are Affected by Incubation Temperature in Wood Ducks (Aix sponsa)

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The University of Chicago Press ABSTRACTRecent research in birds has demonstrated that incubation temperature influences a suite of traits important for hatchling development and survival. We explored a possible mechanism for the effects on hatchling quality by determining whether incubation temperature influences embryonic energy expenditure of wood ducks (Aix sponsa). Because avian embryos are ectothermic, we hypothesized that eggs incubated at higher temperatures would have greater energy expenditure at any given day of incubation. However, because eggs incubated at lower temperatures take longer to hatch than embryos incubated at higher temperatures, we hypothesized that the former would expend more energy during incubation. We incubated eggs at three temperatures (35.0Њ, 35.9Њ, and 37.0ЊC) that fall within the range of temperatures of naturally incubated wood duck nests. We then measured the respiration of embryos every 3 d during incubation, immediately after ducks externally pipped, and immediately after hatching. As predicted, embryos incubated at the highest temperature had the highest metabolic rates on most days of incubation, and they exhibited faster rates of development. Yet, because of greater energy expended during the hatching process, embryos incubated at the lowest temperature expended 20%-37% more energy during incubation than did embryos incubated at the higher temperatures. Slower developmental rates and greater embryonic energy expenditure of embryos incubated at the lowest temperature could contribute to their poor physiological performance as ducklings compared with ducklings that hatch from eggs incubated at higher temperatures.

Transient and permanent effects of suboptimal incubation temperatures on growth, metabolic rate, immune function, and adrenocortical responses in zebra finches

“…Conversely, low incubation temperature raises energy expenditure during development. In wood ducks for instance, total energy expenditure was similar among low, medium and high incubation temperature groups before the start of pipping; however, between pipping and hatching, embryos from the low-temperature group consumed more energy than those from the high and medium groups (DuRant et al, 2011). Olson et al (2006) found that periodic cooling during the incubation period resulted in lighter embryos and less yolk reserve on embryonic day 12.…”

“…In precocial wood ducks, hatchling M b decreased with decreasing incubation temperature (Hepp et al, 2006, but also see DuRant et al, 2010). This is due to the increased energy expenditure during embryonic development at low incubation temperature (DuRant et al, 2011). In altricial zebra finches, periodic cooling to 20°C as opposed to constant incubation temperature of 37.5°C reduced M b on embryonic day 12 without an impact on body size (Olson et al, 2006(Olson et al, , 2008.…”

“…Previous studies show that incubation temperature affects metabolic rates and the hypothalamic-pituitary-adrenal (HPA) axis function in birds for the first 2 weeks of life (DuRant et al, 2010;Nord and Nilsson, 2011): altricial blue tit (Cyanistes caeruleus) nestlings that hatched from eggs incubated at 35.0°C had significantly higher resting metabolic rates at ∼14 days post-hatch (dph; hatch day is 0 dph) compared with nestlings hatched from eggs incubated at 36.5 or 38.0°C (Nord and Nilsson, 2011). Similarly, precocial wood duck (Aix sponsa) embryos that were incubated at 35.0°C expended significantly more energy during the hatching process compared with embryos incubated at 35.9 or 37.0°C (DuRant et al, 2011). The young hatched from eggs incubated at 35.0°C also had significantly higher baseline and stress-induced corticosterone levels compared with ducklings in the 35.9 or 37.0°C groups during the first 9 days of their lives (DuRant et al, 2010).…”

Are thyroid hormones mediators of incubation temperature-induced phenotypes in birds?

“…Consistent with this hypothesis, ducklings with low T 3 hatched later with larger structural size, but in lower body condition, than their counterparts from the high incubation temperature. This suite of effects is attributable to the more protracted growth period associated with slower development at low temperatures [2,4]. In addition, some of the effects of incubation temperature on phenotype appear to attenuate with age [1,7], which could correspond with the convergence of duckling plasma T 3 concentration among incubation temperatures by day 4.…”

“…Thyroid hormones continue to facilitate development post-hatch, influencing the critical transition to homeothermy, and stimulating immune cell proliferation, feeding and metabolism [10,11]. As thyroid hormones are integral to the above processes, many of which are influenced by incubation temperature [1][2][3][4]8], we hypothesized that the phenotypic effects of embryonic incubation temperature are mediated in part by thyroid hormones. Thus, we predicted that (i) ecologically relevant variation in incubation temperature would positively correlate with thyroid hormone concentrations of nestlings and (ii) thyroid hormones would positively correlate with nestling mass, body condition and incubation period, but negatively correlate with tarsus length because of protracted development [2,4].…”