Realistic Fasting Does Not Affect Stable Isotope Levels of a Metabolically Efficient Salamander

Milanovich, Joseph R.; Maerz, John C.

doi:10.1670/12-223

Cited by 8 publications

(7 citation statements)

References 57 publications

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“…(1999) observed that during migration and fasting of Atlantic salmon ( Salmo salar , Salmonidae), only the liver was consistently enriched in δ 15 N, despite protein losses from all other tissues. Results of our study are consistent with previous studies that observed that fasting had no influence on the δ 15 N values of metabolically efficient ectothermic vertebrates adapted to long periods of fasting (Castillo & Hatch, 2007; McCue, 2007; Milanovich & Maerz, 2013). Since lipids were removed before δ 13 C analysis, the steady increase in δ 13 C values with fry fasting was due to the catabolism of carbohydrates rather than 13 C‐depleted lipids.…”

Section: Discussionsupporting

confidence: 93%

How protein quality drives incorporation rates and trophic discrimination of carbon and nitrogen stable isotope ratios in a freshwater first‐feeding fish

et al. 2020

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1. Using stable isotope ratios to explore the trophic ecology of freshwater animals requires knowledge about effects of food quality on isotopic incorporation dynamics. The aim of this experimental study was to: (1) estimate carbon and nitrogen isotopic incorporation rates and trophic discrimination factors (TDFs) of a freshwater first-feeding fish (i.e. salmonid fry) fed three diets that differed only in protein quality (animal or plant or a blend of both); (2) investigate effects of fasting and; (3) evaluate the proportion of each source assimilated when fry were fed a 50:50 animal:plant-based diet. 2. For each diet, incorporation rates of δ 13 C and δ 15 N values were estimated using a time or growth-dependent isotopic incorporation model. Effects of fasting on isotope ratio values were measured regularly until the death of fry. Bayesian stableisotope mixing models were used to estimate the contribution of animal and plant material to fish fed a blend of both food types. 3. Our results show that incorporation rates were lower for fry fed a plant-based diet than for those fed an animal-based diet as growth rate decreased. Timeand growth-dependent models indicated that growth was solely responsible for isotopic incorporation in fry fed an animal-based diet, whereas catabolism increased in fry fed a plant-based diet. After lipid extraction, carbon TDFs were similar regardless of the diet, whereas nitrogen TDFs increased for fry fed a plantbased diet. Long-term fasting induced an increase of 0.63‰ in δ 13 C values of fry in 23 days, whereas δ 15 N values did not vary significantly. Proportions of food sources assimilated by fry fed an animal:plant-based diet were similar to those consumed when using a mixing model with the estimated TDFs, while proportions were unrealistic when using mean TDFs extrapolated from the literature. 4. The results of our study indicate that the quality of food must be considered to use an appropriate timescale to detect changes in fry diets in the field. Moreover, we recommend using different carbon and nitrogen TDFs, one for animal-derived | 1871 NAHON et Al.

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Section: Discussionsupporting

confidence: 93%

How protein quality drives incorporation rates and trophic discrimination of carbon and nitrogen stable isotope ratios in a freshwater first‐feeding fish

et al. 2020

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“…This enrichment in d 15 N should only occur when fasting or starvation is severe enough to cause protein, rather than lipid, catabolism (Martinez del Rio and Wolf 2005;Hatch 2012). However, possibly because of this threshold effect, other studies report no effects of starvation on d 15 N values (Milanovich and Maerz 2013), or even a decrease in d 15 N values (Aguilar et al 2014). Nutritional stress is also expected to result in enrichment of d 13 C due to processing of lipid reserves.…”

Section: Introductionmentioning

confidence: 99%

Effects of fasting and nutritional restriction on the isotopic ratios of nitrogen and carbon: a meta‐analysis

Hertz

Trudel

Cox

et al. 2015

Ecology and Evolution

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Many organisms experience fasting in their life time, and this physiological process has the potential to alter stable isotope values of organisms, and confound interpretation of food web studies. However, previous studies on the effects of fasting and starvation on stable isotopes show disparate results, and have never been quantitatively synthesized. We performed a laboratory experiment and meta‐analysis to determine how stable isotopes of δ 15N and δ 13C change with fasting, and we tested whether moderators such as taxa and tissue explain residual variation. We collected literature data from a wide variety of taxa and tissues. We surveyed over 2000 papers, and of these, 26 met our selection criteria, resulting in 51 data points for δ 15N, and 43 data points for δ 13C. We determine that fasting causes an average increase in the isotopic value of organisms of 0.5‰ for δ 15N and that the only significant moderator is tissue type. We find that the overall effect size for δ 13C is not significant, but when the significant moderator of tissue is considered, significant increases in blood and whole organisms are seen with fasting. Our results show that across tissues and taxa, the nutritional status of an organism must be considered when interpreting stable isotope data, as fasting can cause large differences in stable isotope values that would be otherwise attributed to other factors.

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“…Eventually, when pheretimoid earthworms remove the entire organic horizon, microinvertebrate abundances will decline and salamanders may have to expend more energy to locate prey. Red-backed salamanders have low metabolic rates, are adapted for climate-based shifts in prey availability, and regularly experience periods of starvation (during egg brooding, dispersal, and inhospitable surface conditions) [ 88 ]. So, it is also possible that the effects of pheretimoid earthworm-mediated LL degradation on microinvertebrate prey populations at the sites used for this study may not yet be strong enough to significantly alter salamander body condition.…”

Section: Discussionmentioning

confidence: 99%

Invasive Asian Earthworms Negatively Impact Keystone Terrestrial Salamanders

2016

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Asian pheretimoid earthworms (e.g. Amynthas and Metaphire spp.) are invading North American forests and consuming the vital detrital layer that forest floor biota [including the keystone species Plethodon cinereus (Eastern Red-backed Salamander)], rely on for protection, food, and habitat. Plethodon cinereus population declines have been associated with leaf litter loss following the invasion of several exotic earthworm species, but there have been few studies on the specific interactions between pheretimoid earthworms and P. cinereus. Since some species of large and active pheretimoids spatially overlap with salamanders beneath natural cover objects and in detritus, they may distinctively compound the negative consequences of earthworm-mediated resource degradation by physically disturbing important salamander activities (foraging, mating, and egg brooding). We predicted that earthworms would exclude salamanders from high quality microhabitat, reduce foraging efficiency, and negatively affect salamander fitness. In laboratory trials, salamanders used lower quality microhabitat and consumed fewer flies in the presence of earthworms. In a natural field experiment, conducted on salamander populations from “non-invaded” and “pheretimoid invaded” sites in Ohio, salamanders and earthworms shared cover objects ~60% less than expected. Earthworm abundance was negatively associated with juvenile and male salamander abundance, but had no relationship with female salamander abundance. There was no effect of pheretimoid invasion on salamander body condition. Juvenile and non-resident male salamanders do not hold stable territories centered beneath cover objects such as rocks or logs, which results in reduced access to prey, greater risk of desiccation, and dispersal pressure. Habitat degradation and physical exclusion of salamanders from cover objects may hinder juvenile and male salamander performance, ultimately reducing recruitment and salamander abundance following Asian earthworm invasion.

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Realistic Fasting Does Not Affect Stable Isotope Levels of a Metabolically Efficient Salamander

Cited by 8 publications

References 57 publications

How protein quality drives incorporation rates and trophic discrimination of carbon and nitrogen stable isotope ratios in a freshwater first‐feeding fish

How protein quality drives incorporation rates and trophic discrimination of carbon and nitrogen stable isotope ratios in a freshwater first‐feeding fish

Effects of fasting and nutritional restriction on the isotopic ratios of nitrogen and carbon: a meta‐analysis

Invasive Asian Earthworms Negatively Impact Keystone Terrestrial Salamanders

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