Early-life stress influences ion balance in developing zebrafish ( Danio rerio )
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ORIGINAL PAPER
Early‑life stress influences ion balance in developing zebrafish (Danio rerio) A. J. Hare1,2 · A. M. Zimmer1 · R. LePabic1 · A. L. Morgan1 · K. M. Gilmour1 Received: 6 April 2020 / Revised: 16 September 2020 / Accepted: 29 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract As a key endocrine axis involved in responding to stress, the hypothalamic–pituitary–interrenal axis plays dual roles in mobilizing energy and maintaining ionic/osmotic balance in fishes. Although these roles have been examined independently in detail in adult fishes, less attention has been paid to the effects of an endogenous stress response during early life, particularly with respect to its potential effects on ionic/osmotic balance. The present study tested the hypothesis that exposure of zebrafish to stress during early development would alter ion balance later in life. Zebrafish at three developmental stages (4, 7, or 15 days post-fertilization, dpf) were subjected to an air-exposure stressor twice a day for 2 days, causing elevation of whole-body cortisol levels. Individuals stressed early in life exhibited decreased survival and growth, altered cortisol responses to a subsequent air-exposure stressor, and increased whole-body Na+ and Ca2+ concentrations. Changes in whole-body Ca2+ concentrations were accompanied by increased ionocyte abundance at 7 dpf and increased rates of Ca2+ uptake from the environment. Differences in whole-body ion concentrations at 15 and 35 dpf were not accompanied by altered ion uptake rates. Across all ages examined, air-exposure stress experienced at 7 dpf was particularly effective at eliciting phenotypic changes, suggesting a critical window at this age for a stress response to influence development. These findings demonstrate that early-life stress in zebrafish triggers developmental plasticity, with age-dependent effects on both the cortisol stress axis and ion balance. Keywords Cortisol · Hypothalamic–pituitary–interrenal axis · Stress · Ion balance · Developmental plasticity
Introduction Activation of the hypothalamic–pituitary–interrenal (HPI) axis, and the subsequent glucocorticoid stress response in teleost fishes, as in other vertebrates, orchestrates metabolic, and behavioral adjustments that help the individual deal with a stressor (Barton 2002; Gorissen and Flik 2016; Schreck and Tort 2016; Wendelaar Bonga 1997). However, Communicated by B. Pelster. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00360-020-01319-9) contains supplementary material, which is available to authorized users. * A. J. Hare [email protected] 1
Department of Biology, University of Ottawa, Ottawa, ON, Canada
Department of Integrative Biology, University of Guelph, 50 Stone Rd E, Guelph, ON N1G 2W1, Canada
2
glucocorticoids (with cortisol being the primary glucocorticoid in teleost fishes) also play an important organizational role during early development (Gorissen and Flik 2016; Pankhurst 2016; Nesan an
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