Higley, D. J., Winters, D. G. & Bartels, R. A. Two-dimensional spatial-frequency-modulated imaging through parallel acquisition of line images. Opt. Lett. 38, 1763–1765 (2013). In giant clams, shell opening and closing have been found to be controlled by diurnal light availability [ 3], with the clams basking wide open to optimize photosynthetic production in the daylight hours, and closing partially at night. The clams close when exposed to predation [ 16], temperatures approaching their maximum thermal tolerance [ 3], and to minimize exposure to ultraviolet radiation, such as among intertidal populations [ 4]. Researchers in ethology have increasingly used giant clam shell closure as a model system to understand how mollusks balance food acquisition and predator avoidance [ 16]. Giant clams have eyes that can resolve object sizes [ 17, 18] and evaluate those objects relative to perceived threat [ 19]. The clams can habituate to repeated stimuli and prioritize energy expenditures towards reacting to novel or more severe threats [ 19]. They have also been found to change their valve closure behavior as they grow larger [ 20] and if exposed to distracting stimuli such as noise [ 21]. 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). Our results contrast with a previous culture experiment exposing T. maxima to differing levels of ultraviolet radiation [ 4], where the clams used partial valve closure to reduce the area exposed to UV at all hours. In the Biosphere 2 Ocean, UV exposure is nearly eliminated by the presence of the glass roof above, reducing these clams’ need to utilize such a strategy. More studies are therefore needed into the varying degrees to which valve closure is used as a UV management strategy in wild clams, particularly at differing depths. Arossa S, Martin C, Rossbach S, Duarte CM. Microplastic removal by Red Sea giant clam (Tridacna maxima). Environmental pollution. 2019;252: 1257–1266. pmid:31252123

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 Prevedel, R. et al. Simultaneous whole-animal 3D imaging of neuronal activity using light-field microscopy. Nat. Methods 11, 727–730 (2014). Jolles J. Broad-scale Applications of the Raspberry Pi: A Review and Guide for Biologists. EcoEvoRxiv; 2021. Tran D, Nadau A, Durrieu G, Ciret P, Parisot J-P, Massabuau J-C. Field Chronobiology of a Molluscan Bivalve: How the Moon and Sun Cycles Interact to Drive Oyster Activity Rhythms. Chronobiology International. 2011;28: 307–317. pmid:21539422Rossbach S, Overmans S, Kaidarova A, Kosel J, Agustí S, Duarte CM. Giant clams in shallow reefs: UV-resistance mechanisms of Tridacninae in the Red Sea. Coral Reefs. 2020;39: 1345–1360. Lim SSQ, Huang D, Soong K, Neo ML. Diversity of endosymbiotic Symbiodiniaceae in giant clams at Dongsha Atoll, northern South China Sea. Symbiosis. 2019;78: 251–262. Mondal, P. P., Dilipkumar, S. & Mohan, K. Efficient generation of diffraction-limited multi-sheet pattern for biological imaging. Opt. Lett. 40, 609–612 (2015). In this article, I explain the ins and outs of this simple – yet incredibly powerful – two-light portrait setup. From experimenting with different modifiers to playing with light positions and beyond, I’ll explore all the details to help you master this wonderful lighting technique. By the time you’re finished reading, you’ll know how to create clamshell-lit portraits like a pro (no matter your lighting gear!). If you’re familiar with different types of photography lighting, then you’ve probably come across another, very similar lighting setup:

Ballesta-Artero I, Witbaard R, Carroll ML, Meer J van der. Environmental factors regulating gaping activity of the bivalve Arctica islandica in Northern Norway. Mar Biol. 2017;164: 116. pmid:28546647The higher the light is, the more prominent the shadows that help sculpt the cheekbones will appear.

Lai, H. M. et al. Next generation histology methods for three-dimensional imaging of fresh and archival human brain tissues. Nat. Commun. 9, 1066 (2018). The data from the valvometric sensors in this study support the limited prior observations that wild giant clams bask in the daylight hours and then close to around 20% open at night [ 3], with more valve closures at night than during the day. Similar to the wild-type clams, the Biosphere clams closed to around 30% and experienced more valve closures in the afternoon and nighttime (n = 864 over three months) than during the day (n = 684). This giant clam behavior balances the need to gather photosynthetic energy with the need to avoid predation [ 16]. Closing the valves actively uses energy through exertion of the adductor muscle, while gaping open is energetically “free” due to the elastic hinge ligament. Giant clams therefore spend the brightest hours exposing maximum tissue surface area to sunlight for as long as possible. The short closures were likely “valve clapping” events to expel pseudofeces (excess non-food particles adhered to the gills) [ 37]. We propose that most valve closures at night were related to this filter-feeding activity, based on the average length of those closures. The expelled pseudofeces was visible as “snowdrifts” of fine algal particles surrounding the clams.Cong, L. et al. Rapid whole brain imaging of neural activity in freely behaving larval zebrafish (Danio rerio). eLife 6, e28158 (2017). I like going with a second light, rather than a reflector. It’s easier to control, and doesn’t require any holding–though if you do go with a reflector, you can always have the model hold it, or an assistant of some sort. Evening Out the Second Light Méjean A, Peyraud-Thomas C, Kerbrat AS, Golubic S, Pauillac S, Chinain M, et al. First identification of the neurotoxin homoanatoxin-a from mats of Hydrocoleum lyngbyaceum (marine cyanobacterium) possibly linked to giant clam poisoning in New Caledonia. Toxicon. 2010;56: 829–835. pmid:19895826