These clams (Pholas dactylus) are dazzling to see. From their encased homes, they emit bioluminescent light through their mucus and along their bodies, lighting up parts of the coast for those who take an evening stroll. Pliny the Elder wrote about how they light up the mouths of those eating them. More importantly, they were central to the discovery of the proteins luciferase and luciferin. French pharmacologist Raphael Dubois extracted these proteins, essential to the internal production of luminescence, from Pholas dactylus in the 1880s.