From Brain to Behaviour, How Nanoplastics Associated or not with Methylmercury Influence Zebrafish (Danio rerio)?

Abstract

Plastics, including microplastics (MPs) and nanoplastics (NPs), are ubiquitous in the
aquatic and terrestrial environments. Their massive accumulation caused a growing concern and numerous studies have been carried out to understand their impact. While the toxicity of macro- and microplastics is relatively well studied, the toxicity of nanoplastics is less so. On the other hand, methylmercury (MeHg) is well-known for its neurotoxicity. Although it interact with NPs, the nature of their interaction is still unknown. This present study aims to investigate the impacts of NPs combined or not with MeHg, on nervous system and behaviour in zebrafish (Danio rerio). Neurotoxicity, locomotor toxicity as well as developmental toxicity were considered. After 48 hours of exposure, NPs caused a higher heartbeat rate and a lower apoptosis level in the eye. MeHg alone lead to an increased heartbeat rate within 48 and 72 hours of exposure. The combination of NPs with MeHg also caused a higher heartbeat rate accompanied with an increase in oxygen consumption and hyperactivity. None of the conditions applied had an impact on acetylcholine esterase activity. After 30 days of exposition, changes in brain tissue were noticed in all groups exposed to contaminants. However, results from NPs+MeHg exposed group were always higher than NPs or MeHg alone, bringing arguments to synergistic relationship.
This study demonstrates some toxic impacts on development, locomotion behaviour
and nervous system in zebrafish. Furthermore, it provides new insights into the interaction
between NPs and MeHg.

Date of Award	2024
Original language	English
Awarding Institution	University of Namur UC Louvain
Supervisor	Patrick Kestemont (Supervisor) & Mathilde Oger (Co-Supervisor)