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Group Sex About an hour after sunset, seven days after the full moon in August, star coral polyps, the little animals that make up star coral, had sex. This was not a case of a boy polyp and a girl polyp getting together, finding one another attractive and then discretely engaging in an act of procreation. No, this was a veritable orgy of group sex, with countless millions of polyps openly and shamelessly participating. This bacchanalia of lasciviousness occurs once a year at this time, although according to Steve Simonsen, who has attended more than one of these gala events as a photographer and scientific observer, there are some years in which the mass mating fails to occur. This year, however, was not a time of abstention and in a few hours of orgasmic intensity the polyps ejected their orange bb-sized eggs and cloud-like sperm into the warm tropical waters of the Virgin Islands. Because the sea was perfectly calm the day after the event, you may have noticed the polyp eggs, which looked like large patches of gray foam floating on the surface of the water. There is a good reason behind this sexual madness. The probability that any individual polyp egg will survive long enough to be fertilized, and that the resulting larvae will encounter the right combination of conditions allowing them to grow to maturity is incredibly small. To begin with, the presence of massive quantities of fresh juicy polyp eggs floating about in open water is the equivalent of having a beluga caviar feast held in the parks and plazas of a major city, open to the public and admission-free. There would need to be a staggering amount of caviar in order for there to be some left by the end of the day. This is the situation encountered by the polyp eggs. Fish and other predators emerge from every nook and cranny of the undersea environment to greedily gobble up these tasty morsels. With nothing standing in their way, the predators feast on the eggs until they are completely satiated and can eat no more. Luckily for the polyps, the amount of eggs produced is so great that there is an ample supply leftover after the banquet. However, only some of the surviving eggs will be fertilized and grow into larvae, which is the next stage in the life cycle of a polyp. The helpless larvae have no defense against predators and, along with other plankton, they drift near the ocean surface at the mercy of wind, waves and current. Those that survive eventually settle to the bottom of the sea. To complete its life cycle the star coral larvae must attach itself to a suitable section of the ocean substrate. This could be a rock, an area of dead reef, a pier or concrete piling or an old shipwreck. The base for attachment, in whatever form, must be firm and clean and not already colonized by anything else such as algae or grass. The water where this attachment occurs must be shallow and clear enough to allow sunlight to penetrate. The environment must also be sufficiently circulated by waves or currents in order to supply food and remove wastes. In addition to these conditions the larvae needs water that is clean and pollution-free. Moreover the water must maintain a proper temperature and salinity throughout the year, never being too warm, too cold, too salty or too diluted. The larvae are not in control of where they settle, and those that fall in unsuitable places, which would include almost the entire ocean floor, will soon die. If, however, all of these conditions are met, the larva will produce a limestone outer skeleton and attach itself to the substrate. At this point the larvae has reached maturity and becomes a polyp, an animal rooted to the earth like a plant. The polyp then reproduces itself asexually and an identical polyp is created, the two of them cemented together by limestone. This process of asexual reproduction continues until there is a large colony of polyps all stuck together. This entity, which looks more like a colorful rock than a colony of animals, is what we know of as star coral. In short the probability that a polyp egg will ever become a mature coral is infinitesimally small. The only way to overcome these terrible odds is for the coral polyps to produce astronomically large quantities of eggs and sperm. This is the reason that the annual sexual extravaganza occurs on such a grandiose scale, and this is the reason why star coral still exists on the reefs of the Virgin Islands. |