Shifts in sensitivity of amphibian metamorphosis to endocrine disruption: the common frog (Rana temporaria) as a case study

Katharina Ruthsatz; Kathrin H Dausmann; Katharina Paesler; Patricia Babos; Nikita M Sabatino; Myron A Peck; Julian Glos

doi:10.1093/conphys/coaa100

Shifts in sensitivity of amphibian metamorphosis to endocrine disruption: the common frog (Rana temporaria) as a case study

Conserv Physiol. 2020 Dec 14;8(1):coaa100. doi: 10.1093/conphys/coaa100. eCollection 2020.

Authors

Katharina Ruthsatz^{1

2}, Kathrin H Dausmann¹, Katharina Paesler¹, Patricia Babos¹, Nikita M Sabatino³, Myron A Peck^{4

5}, Julian Glos¹

Affiliations

¹ Institute of Zoology, Universität Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany.
² Zoological Institute, Technische Universität Braunschweig, Mendelssohnstraße 4, 38106 Braunschweig, Germany.
³ Department of Life Sciences, Hamburg University of Applied Sciences, Ulmenliet 20, 21033 Hamburg, Germany.
⁴ Institute of Marine Ecosystems and Fisheries Science, Universität Hamburg, Große Elbstraße 133, 22767 Hamburg, Germany.
⁵ Department of Coastal Systems, Royal Netherlands Institute for Sea Research, PO Box 59 1790, AB Den Burg, Netherlands.

Abstract

Effective conservation actions require knowledge on the sensitivity of species to pollution and other anthropogenic stressors. Many of these stressors are endocrine disruptors (EDs) that can impair the hypothalamus-pituitary-thyroid axis and thus alter thyroid hormone (TH) levels with physiological consequences to wildlife. Due to their specific habitat requirements, amphibians are often sentinels of environmental degradation. We investigated how altered TH levels affected the bioenergetics of growth and development (i.e. age, size, metabolism, cardiac function and energy stores) before, during and after metamorphosis in the European common frog (Rana temporaria). We also determined how ontogenetic stage affected susceptibility to endocrine disruption and estimated juvenile performance. TH levels significantly affected growth and energetics at all developmental stages. Tadpoles and froglets exposed to high TH levels were significantly younger, smaller and lighter at all stages compared to those in control and low TH groups, indicating increased developmental and reduced growth rates. Across all ontogenetic stages tested, physiological consequences were rapidly observed after exposure to EDs. High TH increased heart rate by an average of 86% and reduced energy stores (fat content) by 33% compared to controls. Effects of exposure were smallest after the completion of metamorphosis. Our results demonstrate that both morphological and physiological traits of the European common frog are strongly impacted by endocrine disruption and that ontogenetic stage modulates the sensitivity of this species to endocrine disruption. Since endocrine disruption during metamorphosis can impair the physiological stress response in later life stages, long-term studies examining carry-over effects will be an important contribution to the conservation physiology of amphibians.

Keywords: Amphibian conservation; energy budgets; environmental stress; global change; standard metabolic rate; stress physiology.