Head region of 5 d old zebrafish (Danio rerio) embryos from the negative control (A), embryos exposed to 4 mg/L benzophenone-2 (BP-2; B), and embryos exposed to 7 mg/L BP-2 (C). The micrographs show analysed areas of the greyscale version of the TRITC channel under the fluorescence microscope. An increase in size and intensity of the fluorescence signal after exposure to BP-2 compared to the solvent control (DMSO) could be observed.

Integrated density of the thyroid follicles of zebrafish (Danio rerio) embryos after 5 days of exposure to benzophenone-2 (BP-2; A) and triclosan (TCS; B). BP-2: n = 45–47; TCS: n = 40–47. The central line displays the median and the whiskers are showing the standard deviation. Asterisks indicate statistically significant differences of the exposure groups to the negative control (NC) group: *p < 0.05, **p < 0.01; ****p < 0.0001. SC = solvent control

Changes of the thickness of the photoreceptor layer and its ratio according to the measurement of the outer segment (OS) of the photoreceptor layer (PRL) in the eyes of 5 d old zebrafish (Danio rerio) embryos after exposure to benzophenone-2 (BP-2). Paraffin-section with the visible optical nerve of 4 µm thickness and HE-stained. A Eye of an embryo of the negative control. B Eye of an embryo exposed to 7 mg/L of BP-2. An increase in the overall size of the PRL after treatment with BP-2 was obvious. Likewise, a change in the ratio of the outer and the inner segment (OS, IS) of the PRL is evident due to the increase in the thickness of the OS

Changes of the outer and inner segment (OS/IS) ratio of the photoreceptor layer in the eyes of 5 days old zebrafish (Danio rerio) embryos exposed to triclosan (TCS). Paraffin-sections with the visible optical nerve of 4 µm thickness after HE-staining. A Eye section of an embryo of the negative control. B Eye section of an embryo exposed to 80 µg/L of TCS. An increase in the thickness of the OS of the PRL, associated with an increase of the OS/IS ratio of > 50% was evident

Quantitative changes in the morphology of various layers in the retina of eyes of 5 days old zebrafish (Danio rerio) embryos after exposure to benzophenone-2 (BP-2) or triclosan (TCS). A, B Thickness of the retina. C, D Thickness of the retinal pigment epithelium (RPE). E, F Thickness of the photoreceptor layer (PRL). G, H OS/IS ratios. BP-2: n = 21–33; TCS: n = 30–36. The central line displays the median and the whiskers are showing the standard deviation. Asterisks indicate statistically significant differences of the exposure groups to the negative control (NC) group. *p < 0.05, ****p < 0.0001. SC = solvent control