High absorption of UVR by guanine has been known for decades, however, mostly in the context of mutations in DNA due to the production of the oxidized form of guanine when exposed to UVR – the main reason why UVR is mutagenic ( Kawanishi et al., 2001; Ravanat et al., 2001). However, the role of guanine crystals in iridocytes has received attention only recently. Holt et al. (2014) modeled, based on spectral shifts of irradiance with depth into the Tridacna tissue, the photo-protective role of giant clam role iridocytes. The present experimental data extends these efforts by providing evidence that, in addition to reflection, iridocytes in the T. maxima mantle tissues show a clear absorbance of UVR wavelengths (200–400 nm; Figure 4), consistent with the UVR absorption of pure guanine. Therefore, our results identify a dual role of iridocytes, protecting the animal from high-energetic wavelengths (including UVR), while enhancing the flux of PAR to the symbiont by shifting the UVR radiation absorbed into longer wavelengths within the PAR range, where they can be used by the photosynthetic symbionts. Further, our results provided evidence that the re-emitted longer wavelengths are in fact contributed by guanine (as shown in Figure 6B), the material which composes the optically active components of the iridocytes in Tridacninae, as well as similar guanine-containing structures in other animals (e.g., squid, octopus, and chameleon) ( Rohrlich and Rubin, 1975; Cloney and Brocco, 1983; Teyssier et al., 2015). Photonic Cooperation Leads to the Rich Color Palette and Patterns of Giant Clam Mantles Jacobs, M., Lopez-Garcia, M., Phrathep, O.-P., Lawson, T., Oulton, R., and Whitney, H. M. (2016). Photonic multilayer structure of Begonia chloroplasts enhances photosynthetic efficiency. Nat. Plants 2:16162. Regaudie-de-Gioux, A., Agustí, S., and Duarte, C. M. (2014). UV sensitivity of planktonic net community production in ocean surface waters. J. Geophys. Res. Biogeosci. 119, 929–936. doi: 10.1002/2013jg002566

Technically, you can use clamshell lighting in most portrait situations. It works well on most subjects, and will give you images that are bright and eye-catching. You can use clamshell lighting for family portraits, for corporate headshots, for fashion shots, and much, much more.The datasets generated for this study are available on request to the corresponding author. Author Contributions For every scan, the laser source was automatically cut-off right after a completed scan to minimize potential damages of the tissues due to continuous exposure. The planar and vertical adjustment of the stage, using LabSpec6, allows a fine resolution as low as 1 μm. PL Measurements of Giant Clam Mantle Tissue If you don’t see catchlights in the subject’s eyes, that means your light is too high. Lower the light stand until you get a bit of reflection in the eyes. Cheng, A., Gonçalves, J. T., Golshani, P., Arisaka, K. & Portera-Cailliau, C. Simultaneous two-photon calcium imaging at different depths with spatiotemporal multiplexing. Nat. Methods 8, 139–142 (2011).

Van De Poll, W. H., Eggert, A., Buma, A. G., and Breeman, A. M. (2001). Effects of UV-B-induced DNA damage and photoinhibition on growth of temperate marine red macrophytes: habitat-related differences in UV-B tolerance. J. Phycol. 37, 30–38. doi: 10.1046/j.1529-8817.2001.037001030.x Once you’ve created the “clamshell” setup, with your lights nicely positioned in the shape of a clam, you’ll want to fine tune the strength of the lights. Ishikura, M., Kato, C., and Maruyama, T. (1997). UV-absorbing substances in zooxanthellate and azooxanthellate clams. Mar. Biol. 128, 649–655. doi: 10.1007/s002270050131 The second light should look like the mirror image of the first. This is the bottom half of the shell to the first light.While investigating PL spectra of pure guanine, by exciting them with identical laser excitation sources (633, 473, and 325 nm, respectively), no emission signal (other than noise) was detected when exciting pure guanine with red irradiance at a wavelength of 633 nm ( Figure 6B and Supplementary Table 2). However, emission spectra peaked at 500 nm when excited with a 473 nm source and at 363 nm with a shoulder at 414 nm when excited with 325 nm ( Figure 6B).