Hydrothermal vents along the mid-ocean ridges host ephemeral ecosystems of diverse fauna, including several crustacean species, some of which undergo development as larvae up to 1,000 meters above and 100 kilometers away from the vents. For example, vent crab Bythograea thermydron (at stage of (5) larvae) possess image-forming compound eyes with a visual pigment sensitive to the blue light of upper oceanic waters. As these larvae metamorphose into adulthood and begin to descend to and settle at the vents, they lose their image- forming optics and develop high-sensitivity naked-retina eyes. With maturation, the spectral absorbance of the visual pigment in these eyes also shifts towards (10) longer wavelengths and this progressive visual metamorphosis trades imaging for increased sensitivity, and changes spectral sensitivity to the dim, longer wavelengths of light existing at the bottom of the ocean. As hydrothermal vents produce light, vision may supplement thermal and chemical senses to orient post-larval settlement at vent sites. Which of the following is the most appropriate title for the passage?