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

Abstract

The increased use of silver nanoparticles in consumer and medical products has led to elevated human and environmental exposures. Silver nanoparticles act as antibacterial/antifungal agents by releasing Ag+ and recent studies show that Ag+ impairs neural cell replication and differentiation in culture, suggesting that in vivo exposures could compromise neurodevelopment. To determine whether Ag+ impairs development in vivo, we examined the effects of exposure on survival, morphological, and behavioral parameters in zebrafish embryos and larvae. Methods We exposed zebrafish from 0–5 days post-fertilization to concentrations of Ag+ ranging from 10 nM to 100 µM in order to assess effects on survival and early embryonic development. We then tested whether concentrations below the threshold for dysmorphology altered larval behavior and subsequent survival. Ag+ concentrations ≥3 µM significantly reduced embryonic survival, whereas 1 µM delayed hatching with no effect on survival. Reducing the concentration to as low as 0.1 µM delayed the inflation of the swim bladder without causing gross dysmorphology or affecting hatching. At this concentration, swimming activity was impaired, an effect that persisted past the point where swim bladder inflation became normal; in contrast, general motor function was unaffected. The early behavioral impairment was then predictive of subsequent decreases in survival. Ag+ is a developmental toxicant within concentrations only slightly above allowable levels. At low concentrations, Ag+ acts as a neurobehavioral toxicant even in the absence of dysmorphology.

Developmental lead exposure causes startle response deficits in zebrafish

“…Several research groups have tracked the swim pattern of fish larvae exposed to a range of organic chemicals (Irons et al 2010 [neuroactive drugs]; Jin et al 2010 [bifenthrin]; Powers et al 2010 [Ag + ]; Winter et al 2008 [pharmaceuticals]; Levin et al 2004 [chlorpyrifos]). These experiments, however, used video recording speeds that were sufficient only for tracking general locomotor activity without external physical stressors that would initiate a startle response.…”

Zebrafish model systems for developmental neurobehavioral toxicology

“…These include tasks that measure behavior characteristic of addiction, anxiety, aggression, learning/memory, locomotion, social responses, antipredatory behavior and mate choice. These tasks have been employed for studies of drug abuse (for a review see Ninkovic & Bally-Cuif, 2006), drug development (Levin, 2011) and toxicant exposure (Levin et al, 2003; Powers et al, 2010; Powers et al, 2011). …”

“…However, relatively few studies have examined the effects of developmental exposure to Ag + . High doses of Ag + cause increased mortality while low doses are associated with morphological abnormalities in embryonic and larval zebrafish (Powers et al, 2010). When zebrafish embryos exposed to relatively low concentrations of Ag + reached adulthood, significant differences in the acquisition of spatial discrimination appeared, compared to control animals (Powers et al, 2011).…”

“…Exposure to the insecticide fipronil is associated with notochord degeneration and impaired swimming activity in larval zebrafish (Stehr et al, 2006). Embryonic exposure of zebrafish to silver causes morphological abnormalities and short and long term behavioral perturbations which manifest as reduced swimming activity (Powers et al, 2011; Powers et al, 2010). MeHg exposure has been shown to disrupt startle response in larval zebrafish, increasing the latency to respond and prolonging the duration for which they swim following stimulus presentation (Weber, 2006).…”

Stressing zebrafish for behavioral genetics

“…More recently, extended activity monitoring of larval zebrafish, generally in 96-well microtiter plates has become a reality, as automated methods of larval detection and motion analysis are developed using readily available software [34] or commercially available behavior monitoring software systems. At least two products are active in the zebrafish larval market- ZebraLab software and a zebrabox imaging system (ViewPoint Life Sciences, Montreal, Canada) [109, 110, 114] and EthoVision software combined with an imaging tower (Noldus Information Technology, Wageningen, Netherlands) [107]. Current behavioral monitoring of larval zebrafish work requires a single embryo per well or dish to facilitate tracking movement.…”