A Non-Invasive Water-Borne Assay of Stress Hormones in Aquatic Salamanders

Gabor, Caitlin R.; Zabierek, Kristina; Kim, Diana S.; Barbiano, Laura Alberici da; Mondelli, Megan J.; Bendik, Nathan F.; Davis, Drew R.

doi:10.1643/ot-14-207

Cited by 55 publications

(74 citation statements)

References 38 publications

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“…One way researchers are addressing this issue is by turning to assays of the hormone in hair, feathers, urine or faeces instead of blood. In aquatic animals, it is even possible to measure CORT in the water around the animal (Gabor et al., ). Theoretically, CORT and its metabolites in these materials could reflect plasma levels over a recent period (or, for feathers, during the period of feather growth), and are unlikely to be affected by handling stress associated with sampling (Bortolotti, Marchant, Blas, & Cabezas, ; Narayan & Hero, ; Russell, Koren, Rieder, & Van Uum, ).…”

Section: Glucocorticoid Hormones and Leukocyte Profiles Are Not Intermentioning

confidence: 99%

The use of glucocorticoid hormones or leucocyte profiles to measure stress in vertebrates: What’s the difference?

2018

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Measuring stress in animals is important in many ecological, zoological and veterinary research settings. A common method is to measure plasma levels of glucocorticoid hormones (cortisol, corticosterone, hereafter CORT). Over the past decade, an alternative method has become widely popular: assessing leucocyte profiles; in other words, the heterophil‐to‐lymphocyte ratio (H/L) in birds and reptiles or the neutrophil‐to‐lymphocyte ratio (N/L) in mammals, amphibians and fish. Recent studies have shown that although both indices reliably change after acute stress, they are not always correlated at baseline, and thus are not interchangeable. This lack of correlation has led to some confusion about which of these two measures is “better”; in other words, more biologically relevant and a truer readout of stress. In this review, we first document the dramatic expansion of the use of leucocyte profiles to assess stress over the past decade. We then review published evidence that may explain the discrepancies between leucocyte profiles and plasma CORT. We argue that these discrepancies stem from the nature of the stress reaction and the role of corticosterone (or cortisol) versus leucocytes during the stress response. The differing roles of the two responses translate to differences in the timing of each, which is important for researchers studying either acute or chronic stress. Although plasma glucocorticoids rise within minutes of the onset of acute stress and return to baseline within 1 or 2 hr after the stressor passes, H/L or N/L ratios remain low for at least 30–60 min or sometimes more. The temporal nature of these metrics differs also in the context of long‐term chronic stress. The glucocorticoid response wanes in repeatedly stressed animals, or those exposed to chronic environmental stress, which can often (but not always) lead to low baseline levels and more typically, an attenuated acute stress response. Meanwhile, H/L or N/L ratios appear to remain high under the same conditions. Understanding the temporal differences in the responses should help researchers decide which metric is the better method in their particular study, or whether both would be useful for elucidating different elements of the stress response.

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Section: Glucocorticoid Hormones and Leukocyte Profiles Are Not Intermentioning

confidence: 99%

The use of glucocorticoid hormones or leucocyte profiles to measure stress in vertebrates: What’s the difference?

2018

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“…Analyses of CORT in plethodontids have largely dealt with physiological (rather than developmental) responses in paedomorphic adults (Gabor et al 2016) and terrestrial adults (Wack et al 2013; Thomas et al 2017). Recent experiments indicate synergistic influences of CORT on T 3 -induced metamorphosis in Eurycea tynerensis , (R.M.…”

Section: Is the Metamorphic Response To Thyroid Hormones And Corticosmentioning

confidence: 99%

How Metamorphosis Is Different in Plethodontids: Larval Life History Perspectives on Life-Cycle Evolution

2017

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Plethodontid salamanders exhibit biphasic, larval form paedomorphic, and direct developing life cycles. This diversity of developmental strategies exceeds that of any other family of terrestrial vertebrate. Here we compare patterns of larval development among the three divergent lineages of biphasic plethodontids and other salamanders. We discuss how patterns of life-cycle evolution and larval ecology might have produced a wide array of larval life histories. Compared with many other salamanders, most larval plethodontids have relatively slow growth rates and sometimes exceptionally long larval periods (up to 60 mo). Recent phylogenetic analyses of life-cycle evolution indicate that ancestral plethodontids were likely direct developers. If true, then biphasic and paedomorphic lineages might have been independently derived through different developmental mechanisms. Furthermore, biphasic plethodontids largely colonized stream habitats, which tend to have lower productivity than seasonally ephemeral ponds. Consistent with this, plethodontid larvae grow very slowly, and metamorphic timing does not appear to be strongly affected by growth history. On the basis of this, we speculate that feeding schedules and stress hormones might play a comparatively reduced role in governing the timing of metamorphosis of stream-dwelling salamanders, particularly plethodontids.

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“…We extracted hormones from water and dried samples following Gabor et al [60]. We re-suspended the hormone residue with 95% EIA buffer and 5% ethanol for a total of 230 µL.…”

Section: Water-borne Hormone Methodsmentioning

confidence: 99%

“…We validated the use of the CORT EIA kits for water-borne hormones for A. maculatum. Hormones were extracted from 9 non-experimental animals following [60]. We re-suspended the dried hormone residue in a total of 230 µL of EIA and ethanol to create the pool sample.…”

Section: Water-borne Hormone Methodsmentioning

confidence: 99%

“…For this subset of 64 salamanders, we collected water-borne hormones for CORT analysis on 25 July 2016. We placed each salamander individually in 40 mL of reverse osmosis (RO) water in a petri dish (100 × 15 mm) for 1 h (following [60]). We wore gloves throughout this collection procedure and petri dishes were cleaned with 95% ethanol and rinsed with RO water before use.…”

Section: Introductionmentioning

confidence: 99%

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Cross-Life Stage Effects of Aquatic Larval Density and Terrestrial Moisture on Growth and Corticosterone in the Spotted Salamander

et al. 2018

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For organisms with complex life cycles, conditions experienced during early life stages may constrain later growth and survival. Conversely, compensatory mechanisms may attenuate negative effects from early life stages. We used the spotted salamander, Ambystoma maculatum, to test how aquatic larval density and terrestrial moisture influence juvenile growth, food intake, evaporative water loss and water reuptake rates, and corticosterone levels. We conducted an outdoor mesocosm experiment to manipulate larval density and transferred metamorphosed salamanders into low and high terrestrial moisture treatments in laboratory terrariums. After the larval stage, high-density salamanders were significantly smaller and had higher corticosterone release rates than those from low-density treatments. Salamanders in the low terrestrial moisture treatment consumed fewer roaches, had lower mass-specific growth rates, higher water reuptake, and higher corticosterone release rates than salamanders in high terrestrial moisture treatments. Across moisture treatments, smaller salamanders had higher mass-specific growth rates than larger salamanders. Our results suggest that salamanders can partially compensate for competition in the larval aquatic habitat with increased growth as juveniles, but this response is dependent on terrestrial habitat quality. Thus, the persistence of early life stage effects can be an important, yet context-dependent, component of amphibian life cycles.

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A Non-Invasive Water-Borne Assay of Stress Hormones in Aquatic Salamanders

Cited by 55 publications

References 38 publications

The use of glucocorticoid hormones or leucocyte profiles to measure stress in vertebrates: What’s the difference?

The use of glucocorticoid hormones or leucocyte profiles to measure stress in vertebrates: What’s the difference?

How Metamorphosis Is Different in Plethodontids: Larval Life History Perspectives on Life-Cycle Evolution

Cross-Life Stage Effects of Aquatic Larval Density and Terrestrial Moisture on Growth and Corticosterone in the Spotted Salamander

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