National Geographic : 1963 Mar
surface of the sea. Swimmers and sailors see only its iridescent lavender-blue flotation bladder, or pneumatophore, shaped rather like a distorted football (page 392). Atop the bladder rises the tiny mainsail, a graceful rayed crest of pliant membrane. With this airfoil held erect, the creature ghosts along before the breeze or, some authorities believe, even makes good a quartering course across the wind. To early mariners plying Portuguese waters, the physalia, sailing along with the wind, suggested a galleon under way -hence the popular name. Unseen, below the float, trails the man-of war's armament, its fishing tackle-a fear some array of thin, tenuous tentacles stud ded with thousands of stinging batteries. Portuguese men-of-war first appear on south Florida beaches in late fall. Untrained observers probably could not guess the iden tity of these first arrivals, very little larger than a grain of wheat. Even at this early stage, however, they possess all the equipment of the mature animal. Within a month the phy salias have grown until the average float may measure an inch or more in length. Lethal Armament May Extend 100 Feet By late winter the animal reaches maxi mum size-the float averages eight inches; tentacles may stretch 100 feet. In late April or early May, physalias disappear. Next fall their offspring repeat the life cycle. Although the physalia has simple needs and an uncomplicated way of life, it appears to the scientific observer as a mechanism almost as complex as a space vehicle. Each man-of war is a colony consisting of many parts. Each component represents a distinct individual. Upon the efficient performance of each part depends the life of the colony as a whole. Consider the physalia's most prominent feature, the gaily tinted bladder. Somewhere in the animal's mysterious insides a genera tor operates to keep the pneumatophore filled with a carbon-monoxide-rich gaseous mix ture for buoyancy. Some students believe the physalia can valve out gas, as does a bal loonist. It could then sink below the waves and escape storm-induced turbulence. At sea and in our laboratory tanks we fre quently have seen men-of-war pitching and rolling from side to side, bathing the entire bladder. Edmond L. Fisher's remarkable photograph, made in the Gulf Stream off the Florida coast, captures a physalia righting it self after such acrobatics (page 389). This ma neuver keeps the float moist and may play a 394 part in gas secretion. Another benefit may be the partial absorption of destructive ultravio let light by the thin film of sea water spread over the bladder's exposed surface. Below the bladder dangle many fishing ten tacles, and various kinds of brilliant polyps. Each kind has a special function. Some polyps capture food; others ingest it; still others at tend to the reproductive processes. Physalia can contract its hundreds of long fishing tentacles from many feet to a few inch es in seconds. As winds and currents drive the colony through the water, the tentacles twist and writhe, reaching for food. Each fishing tentacle bears myriad nem atocysts, or stinging capsules, armed with neurotoxin and the mechanism for its in jection. Hundreds of nematocysts are housed KODACHROMES BY FLIP SCHULKE () N.G.S. Living seine seizes dinner for a hun gry man-of-war. Beadlike batteries of stinging capsules kill the victim, photo graphed twice life-size. Doomed guppy, magnified ten times, rises toward the feeding polyps as phy salia contracts its tentacles.