Fig. 2: Intact visual circuit and subcellular visual adaptations in the Greenland shark.

a Immunofluorescent staining of retinal cross-sections from the Greenland shark labelling active (H3K27Ac) and repressed (H4K20me3) chromatin, counter-stained with Hoechst. b Higher magnification image of H4K20me3 and H3K27Ac localization in photoreceptor nuclei (n = 1 individual). Dashed white line demarcates the nuclear membrane. c Distribution of H4K20me3 and H3K27Ac immunofluorescent signal intensity in the nucleus. Dashed line indicates the center of the nucleus. d In situ hybridisation of key retinal cell markers in retinal cross-sections (n = 1). Note that the expression of elovl2, a key gene in synthesis of VLC-PUFAs, is confined to the retinal pigment epithelium cells in the Greenland shark, in contrast to previous work showing zebrafish expression in Müller glia⁷¹ and human expression in cones⁶⁷. e In situ DNA fragmentation detected by TUNEL staining in retinal cross-sections from the Greenland shark (n = 1). DNase I treatment was used as a positive control. f PUFA composition of bovine (n = 5) and Greenland shark retinas (n = 2) showing the relative abundance of each PUFA, normalized to the total signal intensity of all detected PUFAs by liquid chromatography-mass spectrometry (LC-MS). Since LC-MS cannot reliably distinguish between omega-3 and omega-6 species, we have reported only the total number of carbon atoms and double bonds for each lipid species in the panels. Brackets highlight the most abundant sets of PUFAs in each animal’s retina, allowing for a straightforward visual comparison of the relative abundance of specific fatty acids. Scale bars: 25 µm (a, d), 5 µm (b), 10 µm (e). Abbreviations: RPE, retinal pigment epithelium; ONL, outer nuclear layer; INL, inner nuclear layer; GCL, ganglion cell layer. Source data are provided as a Source Data file.