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[AOS16-04] TiO2 nanoparticles inhibit growth of marine single-cell eukaryote, benthic foraminifer Ammonia veneta
Keywords:artificial nanoparticle, toxicity, Foraminifera, long-term incubation
Titanium dioxide nanoparticles (TiO2 NPs) are widely used for industrial products. Such artificial NPs have been accumulated in the marine environment, in particular in coastal area, without decomposition, leading toxic effects on marine ecosystem. Benthic foraminifera, single-cell eukaryote, are distributed from the coastal to deep seafloor, and attract materials of own surroundings by using pseudopodia. This organism could be a good candidate to study such marine toxic effect. The trascriptomic analyses based on Ammonia veneta exposed in 1 ppm TiO2 NPs showed that foraminifers caused the stress (e.g., reactive oxygen species production) due to endocytosis of TiO2 NPs (Ishitani et al., in revision). Moreover, foraminifers withstood such cytotoxicity of TiO2 NPs via extocytosis of nanoparticle encapsulated in ceramide, suggesting their ability of survival in the toxic condition. Here we examined a tolerant limit of a benthic foraminifer in the TiO2 NPs contamination and compared growth rates among specimens treated in different TiO2 NPs concentration throughout 5 weeks incubations.
The exposure experiment with three different concentrations (1, 10, and 50 ppm) of TiO2 NPs showed that the condition with 50 ppm concentration was obviously overdose. Between two feeding frequencies: once and twice per week, the specimens treated in 1 ppm TiO2 NPs had a same growth rate (rate of chamber formation) as that of controls in the seawater. In the other experimental conditions with three different concentrations (1, 5, and 10 ppm) of TiO2 NPs and different amounts of feeding, the specimens of control and 1 ppm TiO2 NPs treatment showed similar growth rates, which were significantly different from those of 5 and 10 ppm NPs treatments. On the other hand, we incubated Chlorophyceae Dunaliella salina, which was the food of foraminifers, in the three different concentrations (1, 5, and 10 ppm) of TiO2 NPs and counted their growth rates. This microalga showed same growth rate between control and 1 ppm TiO2 NPs treatment, whereas it had significantly low growth rates in 5 and 10 ppm NPs treatments. Foraminifers kept extension of pseudopodia in high concentration (10 ppm) of TiO2 NPs. Accordingly, the analysis of the scanning electron microscope with the energy dispersive X-ray spectroscopy indicated some attachment derived from TiO2NPs on the foraminiferal test surface, but no physical changes on the pore where pseudopodia extending from. Thus, the foraminiferal growth rate is affected by the decreasing of food resources rather than toxicity of TiO2 NPs uptake. Although the foraminiferal survival rate was low in the incubations with high concentration TiO2 NPs (5 and 10 ppm), many specimens produced daughter clones in 1 ppm TiO2 NPs. In such low concentration of TiO2 NPs, the future study is available to examine genotoxicity caused by nanoparticle contamination for foraminifers.
[Reference]
Ishitani, Y., C. Ciacci, Y. Ujiie, A. Tame, M. Tiboni, G. Tanifuji, Y. Inagaki, and F. Frontalini, Fascinating strategies of marine organisms to cope with coming pollutant, Titanium dioxide nanoparticle. Environmental Pollution, in revision.
The exposure experiment with three different concentrations (1, 10, and 50 ppm) of TiO2 NPs showed that the condition with 50 ppm concentration was obviously overdose. Between two feeding frequencies: once and twice per week, the specimens treated in 1 ppm TiO2 NPs had a same growth rate (rate of chamber formation) as that of controls in the seawater. In the other experimental conditions with three different concentrations (1, 5, and 10 ppm) of TiO2 NPs and different amounts of feeding, the specimens of control and 1 ppm TiO2 NPs treatment showed similar growth rates, which were significantly different from those of 5 and 10 ppm NPs treatments. On the other hand, we incubated Chlorophyceae Dunaliella salina, which was the food of foraminifers, in the three different concentrations (1, 5, and 10 ppm) of TiO2 NPs and counted their growth rates. This microalga showed same growth rate between control and 1 ppm TiO2 NPs treatment, whereas it had significantly low growth rates in 5 and 10 ppm NPs treatments. Foraminifers kept extension of pseudopodia in high concentration (10 ppm) of TiO2 NPs. Accordingly, the analysis of the scanning electron microscope with the energy dispersive X-ray spectroscopy indicated some attachment derived from TiO2NPs on the foraminiferal test surface, but no physical changes on the pore where pseudopodia extending from. Thus, the foraminiferal growth rate is affected by the decreasing of food resources rather than toxicity of TiO2 NPs uptake. Although the foraminiferal survival rate was low in the incubations with high concentration TiO2 NPs (5 and 10 ppm), many specimens produced daughter clones in 1 ppm TiO2 NPs. In such low concentration of TiO2 NPs, the future study is available to examine genotoxicity caused by nanoparticle contamination for foraminifers.
[Reference]
Ishitani, Y., C. Ciacci, Y. Ujiie, A. Tame, M. Tiboni, G. Tanifuji, Y. Inagaki, and F. Frontalini, Fascinating strategies of marine organisms to cope with coming pollutant, Titanium dioxide nanoparticle. Environmental Pollution, in revision.