Validation and use of 22Na turnover to measure food intake in free-ranging lizards

Gallagher, Kerri; Morrison, David A.; Shine, Richard; Grigg, Gordon C.

doi:10.1007/bf00379323

Cited by 30 publications

(4 citation statements)

References 31 publications

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“…Both our time-dependent model and the data from the introduced enclosure turtles indicate that the time required to reach 0.9 of qeq is =2 yr, =30 times longer than the =24 d required for American Coots (Potter 1987). Measurements of the turnover of other Group IA alkali metals (2 2 Na and 86 Rb) have been used to estimate ingestion rates in the field (e.g., Gallagher et al 1983, Green et a!. Thus, the net effect of the differences in r, a, and keff between endotherms and ectotherms may be best represented by the time required to achieve an effective qeq (rather than by the qeq levels themselves).…”

Section: Discussionmentioning

confidence: 99%

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Environmental Influences on the ¹³⁷Cs Kinetics of the Yellow‐Bellied Turtle (Trachemys Scripta)

Peters¹,

Brisbin²

1996

Ecological Monographs

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Assessments of ecological risk require accurate predictions of contaminant dynamics in natural populations. However, simple deterministic models that assume constant uptake rates and elimination fractions may compromise both their ecological realism and their general application to animals with variable metabolisms or diets. In particular, the temperature-dependent metabolic rates characteristic of ectotherms may lead to significant differences between observed and predicted contaminant kinetics. We examined the influence of a seasonally variable thermal environment on predicting the uptake and annual cycling of contaminants by ectotherms, using a temperature-dependent model of 137 Cs kinetics in free-living yellow-bellied turtles, Trachemys scripta. We compared predictions from this model with those of deterministic negative exponential and flexibly shaped Richards sigmoidal models. Concentrations of 137 Cs in a population of this species in Pond B, a radionuclide-contaminated nuclear reactor cooling reservoir, and 137 Cs uptake by uncontaminated turtles held captive in Pond B for 4 yr confirmed both the pattern of uptake and the equilibrium concentrations predicted by the temperature-dependent model. Almost 90% of the variance in the predicted time-integrated 137 Cs concentration was explainable by linear relationships with model parameters. The model was also relatively insensitive to uncertainties in the estimates of ambient temperature, suggesting that adequate estimates of temperature-dependent ingestion and elimination may require relatively few measurements of ambient conditions at sites of interest. Analyses of Richards sigmoidal models of 137 Cs uptake indicated significant differences from a negative exponential trajectory in the 1st yr after the turtles' release into Pond B. We also observed significant annual cycling of 137 Cs concentrations, apparently due to temperature-dependent metabolism and its influence on ingestion and elimination rates. However, equilibrium concentrations of the radionuclide in the wild population were predictable from negative exponential models based on average annual temperature and its effects on intake and elimination rates, also suggesting that predicting ectotherm responses to long-lived contaminants (such as 137 Cs) may be possible without complex ecophysiological modeling.

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Section: Discussionmentioning

confidence: 99%

“…The annual cycling of [ 137 Cs]s also suggests that a correlation may exist between feeding rates and 137 Cs turnover in the body. Measurements of the turnover of other Group IA alkali metals (2 2 Na and 86 Rb) have been used to estimate ingestion rates in the field (e.g., Gallagher et al 1983, Green et a!. 1986).…”

Section: Discussionmentioning

confidence: 99%

Environmental Influences on the ¹³⁷Cs Kinetics of the Yellow‐Bellied Turtle (Trachemys Scripta)

Peters¹,

Brisbin²

1996

Ecological Monographs

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“…The consequences of different experimental food intake treatments, as well as their resulting effects on growth patterns, physiology of development, and reproduction, have recently received specific attention in amphibians and in reptiles (Cox & Secor, 2007; Secor, Wooten & Cox, 2007). Indeed, analyses on daily energetic metabolism have greatly enhanced our overall knowledge on the metabolic turnover in a number of reptiles (Avery, 1971, 1978; Gallagher et al. , 1983; Bradshaw et al.…”

Section: Introductionmentioning

confidence: 99%

Adaptive significance of food income in European snakes: body size is related to prey energetics

Zuffi

Fornasiero

Picchiotti

et al. 2010

Biological Journal of the Linnean Society

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Feeding strategies and diet patterns have been extensively investigated in vertebrates and, more specifically, in snakes. Although it has been hypothesized that prey species may differ in terms of energy content, almost no theoretical or practical study has been carried out to determine actual nutritional values of the common prey types of wild snakes. Our model taxa were a selection of widely distributed and well known European snake species, which have all been studied in depth: approximately 76% of their diet is composed of mammals, reptiles, and insects. We therefore selected a single model species for each of these categories and proceeded with the analyses. Nutritional values were determined using a standard procedure: lizards and mice were richer in proteins than insects (crickets); insects and mice were richer in lipids than lizards, and mice and crickets have a higher energy content than lizards; lizards were rich in ashes. We then applied our experimental results to a selected sample of European terrestrial snakes (11 populations, ten species, seven genera, two families) characterized by different body size (50-160 cm total length) and reproductive strategies (oviparous versus viviparous), aiming to correlate these parameters with patterns of energy income. A direct relationship was found between body mass/body length ratio (BCI, body condition index) and meal energetics: the higher the BCI, the higher was the metabolic requirement, whereas BCI was independent of species or of reproductive system effect. Large-sized snakes thus need a highly diversified and more energy-rich diet than smaller snakes, supporting previous hypotheses. The simple applicability of this method could be of valuable support in further comparative research work, reducing experimental costs and stimulating further ecological, behavioural, and, possibly, phylogenetic comparisons.

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“…Assuming that all 23 Na intake is from dietary sources (i.e. food, rather than water), then volumes of food consumed can be estimated from the 23 Na content of the most common food sources available [24][25][26]. Hence, using the two radioisotopes in combination allows measurement of both VCO 2 and food intake.…”

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confidence: 99%

Landscape context alters cost of living in honeybee metabolism and feeding

et al. 2017

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Field metabolic rate (FMR) links the energy budget of an animal with the constraints of its ecosystem, but is particularly difficult to measure for small organisms. Landscape degradation exacerbates environmental adversity and reduces resource availability, imposing higher costs of living for many organisms. Here, we report a significant effect of landscape degradation on the FMR of free-flying Apis mellifera , estimated using 86 Rb radio-isotopic turnover. We validated the relationship between 86 Rb k b and metabolic rate for worker bees in the laboratory using flow-through respirometry. We then released radioisotopically enriched individuals into a natural woodland and a heavily degraded and deforested plantation. FMRs of worker bees in natural woodland vegetation were significantly higher than in a deforested landscape. Nectar consumption, estimated using 22 Na radio-isotopic turnover, also differed significantly between natural and degraded landscapes. In the deforested landscape, we infer that the costs of foraging exceeded energetic availability, and honeybees instead foraged less and depended more on stored resources in the hive. If this is generally the case with increasing landscape degradation, this will have important implications for the provision of pollination services and the effectiveness and resilience of ecological restoration practice.

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Validation and use of 22Na turnover to measure food intake in free-ranging lizards

Cited by 30 publications

References 31 publications

Environmental Influences on the ¹³⁷Cs Kinetics of the Yellow‐Bellied Turtle (Trachemys Scripta)

Environmental Influences on the ¹³⁷Cs Kinetics of the Yellow‐Bellied Turtle (Trachemys Scripta)

Adaptive significance of food income in European snakes: body size is related to prey energetics

Landscape context alters cost of living in honeybee metabolism and feeding

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Validation and use of 22Na turnover to measure food intake in free-ranging lizards

Cited by 30 publications

References 31 publications

Environmental Influences on the 137Cs Kinetics of the Yellow‐Bellied Turtle (Trachemys Scripta)

Environmental Influences on the 137Cs Kinetics of the Yellow‐Bellied Turtle (Trachemys Scripta)

Adaptive significance of food income in European snakes: body size is related to prey energetics

Landscape context alters cost of living in honeybee metabolism and feeding

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Product

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Environmental Influences on the ¹³⁷Cs Kinetics of the Yellow‐Bellied Turtle (Trachemys Scripta)

Environmental Influences on the ¹³⁷Cs Kinetics of the Yellow‐Bellied Turtle (Trachemys Scripta)