Neuromotor activity inhibition in zebrafish early-life stages after exposure to environmental relevant concentrations of caffeine

Abstract

Caffeine (CAF), a neuroactive compound, has been found in surface waters at concentrations ranging from few nanograms up to micrograms and may induce adverse effects in aquatic vertebrates. Thus, the aim of this study was to evaluate the potential of CAF in affecting fish early-life stages in a wide concentration range, including occurring levels in surface waters. Specimens of zebrafish in early-life stages were exposed to CAF for 168 h and survival, developmental alterations, locomotor activity and acetylcholinesterase activity were evaluated. CAF induced mortality in embryos unable to hatch or in larvae after hatching (LC₅₀ − 168 h = 283.2 mg/L). Tail deformities were observed in organisms exposed to concentrations ≥ 40 mg/L, while edemas were found at concentrations of 100 mg/L. CAF also decreased the total swimming time and distance moved of exposed organisms (LOEC = 0.0006 mg/L). Locomotor inhibition may be associated with an acetylcholinesterase inhibition observed at concentration ≥ 0.0088 mg/L. Therefore, the hazard of CAF for fish populations deserves further attention since unexpected effects on neuro-behavioral parameters occurs at concentrations often detected in natural aquatic ecosystems.

GRAPHICAL ABSTRACT

Keywords:

• Danio rerio
• embryotoxicity
• acetylcholinesterase
• behavior
• emerging contaminants

Additional information

Funding

This study was partially financed by the “Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES)” - Finance Code 001 (RO: PNPD grant, NOF: PhD grant) and São Paulo Research Foundation – FAPESP (RO: grant no. 2018/03108-0); CKG is grateful to CNPq grant “Bolsas de Produtividade”. The present study also received financial support from the Federal District Research Foundation (FAP-DF; edital da água - 05/2016). Thanks, are also due for the financial support to CESAM (UID/AMB/50017/2019), by FCT/MCTES through national funds. Inês Domingues was funded by national funds, through FCT (Fundação para a Ciência e a Tecnologia, I.P), in the scope of the framework contract foreseen in numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19.