Effects of Copper on the Neuromasts of Xenopus Laevis

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Effects of Copper on the Neuromasts of Xenopus Laevis Paige M. Krupa1   · Scott T. McMurry1 · Matteo Minghetti1 · Jason B. Belden1 Received: 1 August 2020 / Accepted: 26 October 2020 © This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2020

Abstract Fish and aquatic amphibians possess neuromasts on the surface of their body that constitute the lateral line, a sensory system used to detect water displacement. Copper is known to inactivate the neuromast organs of this system. Copper-induced neuromast loss in African clawed frogs, Xenopus laevis, was examined by exposing Nieuwkoop-Faber stage 54–55 larvae to copper concentrations of 0, 100, 200, 300, and 400 µg/L for 96 h, followed by an examination of neuromast counts, staining intensity, and behavioral responses. Neuromasts were counted using a novel imaging method across four different body regions: the whole body, partial body, head, and tail. Neuromast counts showed a decreasing, but nonsignificant, trend across increasing levels of copper exposure. Intensity of neuromast staining showed a stronger concentration-dependent decrease in all four body regions. The decrease in staining intensity, but not neuromast number, may indicate that although neuromasts are still functioning, they have a decreased number of viable hair cells. Potential loss of responsiveness related to neuromast damage was examined via sensitivity to puffs of air at varying distances. We detected little to no difference in response to the air puff stimulus between control tadpoles and tadpoles exposed to 400 µg/L of copper. Neuromasts of X. laevis may be more resistant to copper than those of North American tadpole species, possibly suggesting greater tolerance of the lateral line to environmental stressors in species that maintain this sensory system throughout their lifespan as compared with species that only have the lateral line during the larval period. The ability of organisms to interact with their biotic and abiotic environments is essential for survival and reproduction, and various sensory systems are vital for responding to environmental stimuli. Vertebrates living in aquatic environments use many of the same sensory systems as terrestrial animals, including vision, somatasense, olfaction, and auditory (Collin and Marshall 2008). Some aquatic species possess electroreception (Collin and Marshall 2008). Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s0024​4-020-00778​-z) contains supplementary material, which is available to authorized users. * Paige M. Krupa [email protected] Scott T. McMurry [email protected] Matteo Minghetti [email protected] Jason B. Belden [email protected] 1



Department of Integrative Biology, Oklahoma State University, 501 Life Sciences West, Stillwater, OK 74078, USA

Additionally, fish, larval amphibians, and some adult aquatic amphibians have a mechanosensory lateral line system (Russell 1976) comprised of an array of neu