Exploring combined effects of arsenic and selenium exposure on larval zebrafish (Danio rerio)

Arsenic contamination in aquatic ecosystems is a major environmental concern, with arsenite (As³⁺) being highly toxic. Selenium (Se) helps mitigate oxidative stress and hence could reduce the toxic effects of arsenic. However, Se can also be toxic at high concentrations. Given that these metalloids commonly co-occur in the environment, there is a pressing need for further research into their combined effects on aquatic life. To investigate this interplay, zebrafish embryos were exposed to As alone (as arsenite) or in combination with two different chemical forms of Se including As 120 μg/L alone (as arsenite), As 120 μg/L + Se 25 μg/L (as selenite), As 120 μg/L + Se 120 μg/L (as selenite), and As 120 μg/L + Se 2.5 μg/L (as selenomethionine, SeMet) until 4 days post-fertilization. There was no significant difference in the survival, hatching and deformity rate when fish were exposed to both As and Se. Co-exposure to As and Se significantly affected thigmotactic behaviour and reflexive movement (for all p < 0.001), with 2.5 µg/L Se mitigating As-induced impairments. While reactive oxygen species (ROS) levels were elevated in larvae exposed to As alone and As + Se 25 µg/L, there was a markedly reduced ROS level in the As + Se 120 µg/L and As + SeMet 2.5 µg/L treatments, highlighting selenium’s antioxidant efficacy. A marked suppression of genes related to antioxidant (Mn-SOD, gpx), neurogenesis (ngn1, hucs, bdnf, sf1), dopaminergic (Sncgb, otpa, robo2, th1), serotonergic (pet1, tph2), and motor neuron (pax2a) was observed following arsenic exposure. At the same time, co-treatment with As + Se 25 µg/L partially restored nrf2a expression (p < 0.05). These findings highlight the potential for naturally co-occurring Se to modulate As toxicity in aquatic environments, underscoring the importance of considering chemical interactions when assessing ecological risks.

Name thesis:degree_name

Master of Science (M.Sc.)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Biology

Grantor

University of Saskatchewan

Year dc:date.issued

2025

Author dc:creator

• Luo, Owen H

Advisors dc:contributor.advisor

• Chivers, Douglas
• Niyogi, Soumya

Committee members dc:contributor.committeemember

• Ferrari, Maud
• Weber, Lynn

• Arsenic
• Selenium
• Zebrafish
• Toxicity

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10388/17549

OAI identifier oai:identifier

oai:harvest.usask.ca:10388/17549