Pond Acidification May Explain Differences in Corticosterone among Salamander Populations

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.. ABSTRACT Physiological tolerances play a key role in determining species distributions and abundance across a landscape, and understanding these tolerances can therefore be useful in predicting future changes in species distributions that might occur. Vertebrates possess several highly conserved physiological mechanisms for coping with environmental stressors, including the hormonal stress response that involves an endocrine cascade resulting in the increased production of glucocorticoids. We examined the function of this endocrine axis by assessing both baseline and acute stress-induced concentrations of corticosterone in larvae from eight natural breeding populations of Jefferson's salamander Ambystoma jeffersonianum. We surveyed individuals from each pond and also examined a variety of environmental pond parameters. We found that baseline and stress-induced corticosterone concentrations differed significantly among ponds. Population-level baseline corticosterone concentrations were negatively related to pH and positively related to nitrate, and stress-induced concentrations were again negatively related to pH, positively related to nitrate, and positively related to temperature. We followed the field survey with an outdoor mesocosm experiment in which we manipulated pH and again examined baseline and acute stress-induced corticosterone in A. jeffersonianum larvae. As in the field survey, we observed an increase in the baseline corticosterone concentration of individuals exposed to the lowest pH treatment (pH 5-5.8). Examining physiological indices using a combined approach of field surveys and experiments can be a powerful tool for trying to unravel the complexities of environmental impacts on species distributions. The University of Chicago Press

Multifarious selection through environmental change: acidity and predator-mediated adaptive divergence in the moor frog (Rana arvalis)

“…First, elevated corticosterone levels may facilitate predator-induced increases in tail depth and its levels can correlate positively with pond predator densities [46]. Second, as acidic conditions may increase corticosterone expression [47], the relatively deeper tails in the acidic populations, as well as within the acidic treatment, seen here may reflect higher corticosterone expression. Third, corticosterone also mediates locomotor and feeding activity of tadpoles [48]-possibly providing a link between the observed increased activity (in the absence of predators) and increased tail depth in acidic ponds.…”

Stress and chytridiomycosis: Exogenous exposure to corticosterone does not alter amphibian susceptibility to a fungal pathogen

“…These "non-detect" data, with chemical concentrations below or above assay detection limits, represent a common example of censored data (Kent and Funk, 2004;Helsel, 2005a). We recently applied censored regression that explicitly accounts for "non-detect" observations (Helsel, 2005a, b) in two endocrine studies examining corticosterone concentrations in larval amphibians (Chambers et al, 2011(Chambers et al, , 2013. We follow a similar approach here for corticosterone comparisons (outlined in S-Methods).…”

“…Amphibians will also elevate corticosterone into a reactive homeostasis range in response to stimuli, but these responses can vary with life stage (Crespi and Denver, 2005). In larvae, corticosterone can be elevated in response to crowding, food deprivation (Glennemeier and Denver, 2002c;Crespi and Denver, 2005), confinement (Glennemeier and Denver, 2002a;Belden et al, 2010), and acidic conditions (Chambers et al, 2013). Corticosterone elevation at the larval stage can lead to altered growth and development (Glennemeier and Denver, 2002b) and increased susceptibility to infectious disease (Belden and Kiesecker, 2005).…”

Physiological Stress Responses in Amphibian Larvae to Multiple Stressors Reveal Marked Anthropogenic Effects even below Lethal Levels

“…Amphibians are also deeply affected by human disturbances and indeed constitute the most threatened group of vertebrates (Hoffman et al 2010). CORT regulation is a common stress response in anuran tadpoles to pond drying, pollutants, predators, acidification, or UV-B radiation (Glennemeier and Denver 2001;Chambers and Belden 2009;Burraco et al 2013;Chambers et al 2013;Maher et al 2013). However, CORT regulation has many potential cascading effects on other aspects of amphibian biology, and these are seldom studied.…”