Figure 4.

Effects of SiO₂NPs on Hydra regeneration. Forty eight-hours-regenerating Hydra treated with 25 nM SiO₂NPs (A); 48 h-regenerating Hydra treated with 10 nM SiO₂NPs (B); untreated 48 h-regenerating Hydra (C). In (D), the histogram shows the distribution of polyps developmental stages; stage 0 indicates absence of tentacles; stage 1 indicates the presence of tentacle buds; stage 2 indicates new emerging tentacles. Animals treated with 25 nM SiO₂NPs are significantly impaired in the regeneration process. Data are means of three independent experiments. Twenty-five animals for each experiment were employed. Bar (A–C), 1 mm.