National Geographic : 1971 Aug
Science's Window on the Sea By far the most persistent forager I en countered was a gray-and-turquoise queen triggerfish that had her eye on a succulent but spiny sea urchin. The triggerfish repeat edly lifted the urchin off the bottom by one spine in an attempt to dive beneath and attack the creature's undefended portion. Each time, however, the urchin touched bottom first and set off directly toward the safety of the reef. Finally the triggerfish charged head-on at its prey, receiving a spine or two in the nose while cracking it open. I'm convinced that the many triggerfish I have seen with purple noses were veterans of similar en counters; they had been tattooed by their pin cushion prey. Annoyed Lobster Mounts an Attack Initial results of the spiny-lobster study added considerably to the knowledge I had gained the year before during Tektite I. Unlike his solitary New England cousin, the spiny lobster is a sociable creature, often crowding 15 or 20 strong into a single den. By comparing our head count against the past year's figures, we determined that the lobster population of Great Lameshur Bay reef had remained roughly constant. The census was merely the first stage in our study. During our second week, Ian and I turned to the subject of lobster behavior and began prowling the sea at night. Like the basket star, octopus, moray, and certain types of shrimp, the spiny lobster is nocturnal. Only when darkness overtakes the reef does he forsake the security of the den. Under cover of night he roams the sandy plains adjoining the reef, foraging for snails, oysters, clams, and other mollusks, keeping an eye out for his two great enemies, the shark and the giant grouper. Few other creatures care to trifle with an adult Panulirus:Pound for pound he is a match for most predators. My New England friends, accustomed to the massive claws of their native lobster, consider Panulirus a poor defenseless cray fish. Although he lacks claws, Panulirus is surprisingly well armed. In addition to his spiny shield, he packs tremendous power in a set of ten sharp-pointed legs and in a mouth that can crack the quarter-inch-thick shell of a conch to get at the luckless inhabitant. Those who dismiss Panulirusas a timid and harmless creature would do well to consider Ian's brush with a six-pound male. Had it happened to an inexperienced diver, he could have been in serious trouble. The mishap occurred during a short earlier dive, while Ian and another diver were sur veying the inshore waters for lobsters. They were working with standard scuba gear at a depth of 35 feet, well separated but within sight of each other. Ian's partner had just spotted a young lobster and was reaching down to snare it, when some sixth sense made him glance in Ian's direction. Ian was no longer on the bottom. A vanish ing column of bubbles indicated that he had surfaced abruptly. Ian is an experienced diver, and nothing short of an emergency would cause him to leave a partner below without warning. Following Ian's bubbles, his part ner reached the surface and found him grap pling with a large male lobster. Once Ian got rid of his attacker, he told what had happened. In a crevice of the reef he had spied a fairly large lobster, measuring a foot and a half in length. After snaring it with his nylon loop, he picked it up in the proper fashion behind the carapace and started loosening the loop. "I must have held it too close to me," Ian said, "because the next thing I knew it had pulled my face mask down around my neck and pried the air regulator out of my mouth." With only seconds to act, Ian took off for the surface 35 feet overhead. There he caught a breath and managed to free himself. Had the accident occurred during our time in the habitat, Ian's predicament would have been even more serious. Prevented from sur facing under threat of the bends, he would have had to fight the lobster underwater for his scuba gear. One of the major puzzles regarding the Daddy longlegs of the deep, an arrow crab on a midnight stroll am bles past black-spined sea urchins and a tomato-red sponge (following pages). Tektite divers, logging countless night hours with their miner type head lanterns, found that such daytime foragers as parrotfish and wrasse surrender the reef to a strikingly different nocturnal population. ABOUT5 TIMESLIFE-SIZE;EKTACHROME © N.G.S.