Silver exposure in developing zebrafish (Danio rerio): persistent effects on larval behavior and survival

Area of Science:

• Environmental toxicology
• Developmental neuroscience
• Nanomaterial safety

Background:

• Increased use of silver nanoparticles (AgNPs) leads to higher human and environmental exposure.
• AgNPs release silver ions (Ag+) which impair neural cell replication and differentiation in vitro.
• Potential for Ag+ exposure to compromise neurodevelopment in vivo.

Purpose of the Study:

• To determine if Ag+ impairs neurodevelopment in vivo.
• To assess the effects of Ag+ exposure on zebrafish survival, morphology, and behavior.
• To investigate Ag+ toxicity at concentrations below the threshold for gross morphological defects.

Main Methods:

• Zebrafish embryos and larvae (0-5 days post-fertilization) were exposed to Ag+ (10 nM to 100 µM).
• Evaluated effects on survival, embryonic development, hatching, swim bladder inflation, and larval behavior.
• Assessed swimming activity and general motor function at sub-dysmorphology concentrations.

Main Results:

• Ag+ concentrations ≥3 µM significantly reduced embryonic survival.
• 1 µM Ag+ delayed hatching; 0.1 µM Ag+ delayed swim bladder inflation without gross malformations.
• Low-level Ag+ (0.1 µM) impaired swimming activity, predicting decreased survival, despite normal swim bladder inflation later.

Conclusions:

• Silver ions (Ag+) are developmental toxicants at concentrations near allowable levels.
• Ag+ acts as a neurobehavioral toxicant at low concentrations, even without causing visible malformations.
• Early behavioral deficits induced by Ag+ can predict subsequent survival outcomes.