Arms control

Natural History, April, 2002 by Judy Rice

Off the coast of British Columbia, a sunflower sea star prepares to spawn, using a dozen or so arms to hoist its fleshy central mass free of the seafloor. The hunched posture is typical of female stars, which shoot a stream of eggs upward to be fertilized by drifting sperm. But this static pose belies the mobility of the species. Fleet, large, and voracious, the sunflower sea star roams cool shallow Pacific waters hunting down assorted shellfish, urchins, and fishermen's bait. "You can often see a whole gang of them under a dock," reports one biologist, ominously.

The sunflower sea star can be a full thirty inches in diameter. Despite its proportions, it is the cheetah of its habitat, flexible and--carried on tube feet, the many tipped bristles on its underside--able to reach speeds of rive feet a minute. Prey is first enveloped, then digested by the star's everted stomach. "I have seen swimming scallops scattering in front of a large star," says photographer Fred Bavendam, who also witnessed cannibalism: "I lifted up a sunflower sea star that was on top of another. On the bottom one I could see a `munched' area."