Source question 22. 5 GO ON TO THE NEXT PAGE. ACT-Z04 1 1 PASSAGE II Glowing on an Adventure As I pulled my camera out of my backpack, I felt a tap on my arm. “No photographs,” whispered the woman next to me, pointing up to the cave ceiling. “The flash will make them stop glowing,” she said, whispering. She was referring to the thousands of glowworms that clung to the limestone ceiling and, with their radiant bodies, flooded the cave in aquamarine light. While I was traveling on canoe on a group tour through the renowned Glowworm Grotto of New Zealand’s Waitomo Caves. Were it not for the twinkling light of these Arachnocampa luminosa, a species unique to New Zealand and abundant in these caves, this meandering subterranean passageway would feel as though it were downright ensconced in shadows. I sheepishly tucked the camera away and focused again on the glowworms. Collectively, they resembled the cosmos, a sea of stars in a clear night sky. Beautiful—yet what made them glow? “Bioluminescence,” the woman said, peculiarly sensing my curiosity. 5 A badge was pinned to her shirt indicated she was a biochemist, here, I guessed, to research the organism. 16 17 18 19 20 22 She explained that to attract prey, glowworms (not really worms at all, but the larval stage of a fungus gnat) emit light through their translucent skin; via a cellular chemical reaction. The cells produce luciferin, a chemical pigment that reacts with oxygen to produce light that shines through the organism’s tail-end intestine. From its mouth, she showed me, all glowworms dangle shimmering silken threads glossed in beads of mucus. Cave-dwelling insects are trapped in these threads, then reeled in like fish on a line, and finally lured by the light. The light responds to environmental factors. The sound of splashing water, however, might signal that prey is nearby, causing them to brighten. <
