Factors Influencing the Turnover and Net Isotopic Discrimination of Hydrogen Isotopes in Proteinaceous Tissue: Experimental Results Using Japanese Quail

Abstract

Stable hydrogen isotopes (δ(2)H) are commonly used in studies of animal movement. Tissue that is metabolically inactive after growth (e.g., feathers) provides spatial or dietary information that reflects only the period of tissue growth, whereas tissues that are metabolically active (e.g., red blood cells) provide a moving window of forensic information. However, using δ(2)H for studies of animal movement relies on the assumption that tissue δ(2)H values reflect dietary δ(2)H values, plus or minus a net diet-tissue discrimination value, and that the turnover rate is known for metabolically active tissue. The metabolic rate of an animal may influence both diet-tissue discrimination values and isotopic tissue turnover rate, but this hypothesis has not been tested experimentally. To examine the metabolic hypothesis, an experimental group of 12 male and 15 female captive Japanese quail (Coturnix japonica) was housed at 8.9°C for 90 d to elevate their metabolic rates (mL CO(2) min(-1)), and a control group of 12 male and 13 female quail was housed at room temperature during the same period. For both experimental and control birds, diet-tissue discrimination values were estimated for red blood cells and feathers. To determine turnover rate, experimental and control birds were switched from a (2)H-enriched diet to a (2)H-depleted diet, with red blood cells sampled before and after diet switch. Metabolic rate did not influence red blood cell hydrogen isotope turnover rate (η(2)(p) = 0.24)) or diet-feather isotope discrimination values (η(2)(p) = 0.86). Diet-feather hydrogen isotopic discrimination had a significant sex plus treatment interaction effect; female feathers were depleted in (2)H relative to food regardless of treatment, whereas male feathers were enriched in (2)H. The effect of sex suggested that experimental studies should examine whether coeval males and females differ in blood δ(2)H levels during certain periods of the annual cycle.

Expanding the Isotopic Toolbox: Applications of Hydrogen and Oxygen Stable Isotope Ratios to Food Web Studies

“…Nevertheless, these shifts can provide an opportunity to examine ecological strategies of resource use (Wunder et al, 2012). Little work has addressed turnover with respect to H and O isotope ratios specifically, and tissue-specific times derived from other systems may or may not apply (O'Brien and Wooller, 2007;Podlesak et al, 2008;Storm-Suke et al, 2012).…”

“…Other characteristics of an organism's life history, habitat, and physiology may result in variability in δ 2 H and δ 18 O values, including species, size, age class, trophic position, habitat stratification, drinking behavior, metabolic rate, routing, and tissue type (Tuross et al, 2008;Kirsanow and Tuross, 2011;Soto et al, 2011Soto et al, , 2013bWolf et al, 2011Wolf et al, , 2012Storm-Suke et al, 2012;Graham et al, 2013;Crowley et al, 2015).…”

“…Metabolic rate is closely linked to body size, but within organisms of similar body mass, it can be sensitive to factors such as diet and thermophysiology (Bryant and Froelich, 1995). For example, the relative contribution of drinking water to avian feather H increases with increasing metabolic rate, which was experimentally elevated by housing quail at colder temperatures (Storm-Suke et al, 2012). Total water flux, defined as the amount of water into and out of an animal each day, also scales with body size, but can respond to other factors, such as dietary inputs and environmental temperature (Bryant and Froelich, 1995).…”

“…Additionally, little is known about the turnover times for H and O isotopes Storm-Suke et al, 2012;Wolf et al, 2012), which is necessary to quantify the time frames over which organisms reflect changes in the diet, drinking water, and environment. Controlled feeding studies with changes in diet and/or drinking water are needed to characterize the integration periods and turnover patterns of these elements in organismal tissue.…”

Stable isotope analyses as a forensic tool to monitor illegally traded African grey parrots

“…It was suggested that primary feathers of bullfinches Pyrrhula pyrrhula and greenfinches Carduelis chloris grow slower than both body and tail feathers (Newton, 1967) and thus assimilate nutrients at different rates; this may also apply to African grey parrots. An alternative explanation could be the routing of d 13 C and d 15 N to different tissues or from different body pools for different tissues/feather types (Gannes et al, 1997;Bearhop et al, 2002;Ayliffe et al, 2004;Dalerum & Angerbjӧrn, 2005;Fox et al, 2009;Grecian et al, 2012;Storm-Suke, Norris & Wassenaar, 2012).…”