Davis, with colleagues in the Johnsen Lab and the Smithsonian, trawled Monterey Bay and the Gulf of Mexico for fish living a mile deep, where almost no light penetrates.  The results of their quest have been published in “Ultra-black Camouflage in Deep-Sea Fishes."  Predators at that depth use bioluminescence to locate prey.  After finding 18 different species, Davis et al. used the wavelength of available light in the “Midnight Zone” (480 nanometers) to measure how much light each fish reflected back.  Sixteen qualified as “ultrablack,” having less than 0.5% reflectance—which made them very difficult to photograph!  After studying skin samples with electron microscopy and spectrophotometry, the researchers determined that these fish have tightly packed, spherical melanosomes which form a continuous layer covering the body.  Normal black skin has pearl-shaped melanosomes with space between them that reflects light effectively. 

Could this be the secret of Romulan starships’ infamous cloaking ability?  Only further research will tell!