Eugenol exposure inhibits embryonic development and swim bladder formation in zebrafish

Area of Science:

• Aquatic toxicology
• Developmental biology
• Fish physiology

Background:

• Eugenol, a clove-derived essential oil, is widely used for its anesthetic properties in aquaculture.
• The potential developmental toxicity of eugenol, particularly during early fish life stages, remains under-explored.
• Massive eugenol use in aquaculture raises safety concerns for aquatic organisms.

Purpose of the Study:

• To investigate the developmental toxicity of eugenol exposure in zebrafish (Danio rerio) embryos.
• To elucidate the underlying molecular mechanisms, focusing on the Wnt/β-catenin signaling pathway.
• To assess the impact of eugenol on hatching, growth, swim bladder development, and larval survival.

Main Methods:

• Zebrafish embryos were exposed to varying concentrations of eugenol (0–30 mg/L) for 96 hours post-fertilization.
• Evaluated developmental endpoints including hatching rate, body length, and swim bladder inflation.
• Utilized real-time quantitative polymerase chain reaction (qPCR) to analyze gene expression related to the Wnt/β-catenin pathway.

Main Results:

• Eugenol exposure significantly delayed zebrafish hatching and reduced body length and swim bladder inflation in a dose-dependent manner.
• Increased mortality was observed in eugenol-exposed zebrafish larvae.
• qPCR analysis revealed significant alterations in Wnt/β-catenin pathway gene expression, including upregulation of wif1 and downregulation of fzd3b, fzd6, ctnnb1, and lef1.

Conclusions:

• Eugenol exposure induces developmental toxicity in zebrafish, primarily by inhibiting the Wnt/β-catenin signaling pathway.
• Swim bladder malformation due to pathway inhibition is a critical factor in zebrafish larval mortality.
• These findings highlight the risks associated with eugenol use in aquaculture and its impact on early fish development.