S5: Environmentally Relevant Exposures of Nanomaterials...
Environmentally Relevant Exposures of Nanomaterials in Various Life Stages using Japanese Medaka
Realistically, considering all life stages, fish have various routes of exposure to a variety of aquatic contaminants. For early life stages, exposure may have come from the parent and depending upon the site for egg and larval development, additional exposure may occur via water. Adult life forms may feed upon contaminated food organisms or take up materials over the gills or other surficial tissues. The small aquarium model fish, Japanese medaka (Oryzias latipes), with its wide salinity tolerance and superior imaging properties of developmental forms enables detailed descriptions of phenotypic alterations following exposures ranging from fresh- to marine waters. The model allows us to mimic realistic conditions and toxicant exposure in a controlled laboratory setting over short periods of time to localize uptake and response in various life stages. Our general approach is to identify and characterize effects of bulk materials prior to studies of their nano-sized counterparts. In our hands, dietary exposure to selenomethione affected the offspring of exposed parents and embryos exposed to nano-selenium (nanoSe) revealed altered survival, hatching, and development. The coatings of silver nanoparticles (AgNPs) matter significantly in their toxicity to hatchlings. Following nanomaterial exposure, we use high resolution microscopy to hunt for sites of uptake and distribution as well as tissue response. Our acquisition of the transparent Quintet strain of medaka has increased clarity of in vivo observations through the adult body wall prior to any further ex vivo studies. The pinpointing of areas of interest, prior to further processing, greatly enhances our high resolution studies in light and electron microscopy. Recently, we have tested Quintets for effects of ingested microplastics. This use of the medaka model has shown how life stage plays an important role in exposure. Our evaluation of responses at specific tissue sites ground proofs host reactions, while providing economy of time and statistical precision.