Embryonic exposure to environmentally relevant concentrations of triclosan impairs foraging efficiency in zebrafish larvae

Abstract

The ubiquitous and persistent contaminant triclosan is known to cause developmental and behavioral toxicity in fish, but few studies have evaluated the long‐term effects of these responses. We used a phenotypically anchored approach to evaluate the behavioral responses caused by early exposure to environmentally relevant concentrations of triclosan to better understand the risk triclosan poses to fish. Zebrafish were exposed to 0, 0.4, 4, or 40 μg triclosan/L (nominal concentrations) for 5 d followed by depuration for 16 d to assess effects on mortality, development, and foraging efficiency. Because foraging efficiency can be impacted by neurological and structural alterations, we assessed morphological and behavioral indicators of neurotoxicity and morphology of craniofacial features associated with gape to identify potential underlying mechanisms associated with altered foraging behaviors. To our knowledge, we are the first to show that early exposure to environmentally relevant concentrations of triclosan impairs foraging efficiency in larval fish by 10%, leading to emaciation and reduced growth and survival. The cause of the impacts of triclosan on foraging efficiency remains unknown, because effects were not associated with overt indicators of neurotoxicity or grossly malformed craniofacial structures. Our results suggest that early exposure to triclosan has the potential to impact the sustainability of wild fish populations, and thus the mechanism underlying behavioral alterations following exposure to triclosan warrants further study. Environ Toxicol Chem 2018;37:3124–3133. © 2018 SETAC

Developmental exposure to triclosan and benzophenone-2 causes morphological alterations in zebrafish (Danio rerio) thyroid follicles and eyes

“…This is in line with observations by Kim et al ( 2018 ), who described a smaller eye diameter in zebrafish exposed to TCS. A decrease in eye diameter was also evident in zebrafish embryos exposed to other TPO inhibitors such as PTU (Baumann et al 2016 , Reider and Connaughton 2014 ) and could be correlated to impaired foraging efficiency of zebrafish embryos after exposure to TCS (Wirt et al 2018 ). Whereas the thickness of the RPE did not respond to TCS exposure, changes in PRL thickness showed a monotonic increase over water and DMSO controls with increasing TCS concentrations.…”

A Short Review of the Toxicity of Dentifrices—Zebrafish Model as a Useful Tool in Ecotoxicological Studies

“…Once triclosan levels are detected in various human tissues such as adipose tissue, brain, and liver [ 55 , 56 ], studies on its long-term effects on human health have been undertaken [ 57 ]. Toxic effects of triclosan have been also extensively evaluated using zebrafish as an animal model [ 58 , 59 , 60 , 61 ]. Triclosan’s mechanisms of toxicity encompass a range of effects on zebrafish, including endocrine disruption, oxidative stress, microbiota imbalance, altered behavior, and developmental and reproductive effects.…”

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“…Reduced eye size, an indicator of neurotoxicity, was also observed in zebrafish embryos exposed to more than 0.4 μg/L triclosan. [ 63,68 ]…”

“…Reduced eye size, an indicator of neurotoxicity, was also observed in zebrafish embryos exposed to more than 0.4 μg/L triclosan. [63,68] Several studies have reported triclosan-induced neurotoxicity using cell culture as experimental system. Triclosan-induced apoptosis in mouse neocortical neurons, mouse neuronal progenitor cells, and rat neural stem cells.…”