The Starfish Eaters

The scholarly paper that German Zoologist Wolfgang Wickler presented at a scientific meeting in Tanzania last January dealt, among other subjects, with sexual fidelity in the animal world. For two members of the conference, Ecologist Lee Talbot and his biologist wife Martha, both of the Smithsonian Institution, his remarks were of more than academic interest. They provided an exciting clue that might well lead to control of the crown-of-thorns, the giant starfish that is literally eating away vital coral reefs in the Pacific (TIME, Sept. 12).

In discussing creatures that form lasting bonds with their mates (jackals, gibbons, geese, etc.), Wickler included Hymenocera elegans, or the painted shrimp. Almost in passing, he mentioned that the shrimp feeds on starfish, including the crown-of-thorns. To the Talbots, who have been looking for ways to cope with the sudden and mysterious proliferation of the crown-of-thorns, the beautifully colored russet-and-white shrimp seemed a promising answer.

Soft Underbelly. At the Talbots' request, Wickler set up a demonstration of the painted shrimp's effectiveness; he staged an extraordinary laboratory encounter between a crown-of-thorns and a pair of painted shrimps.* It was hardly a match. Oblivious to the starfish's poisonous spines, the shrimps quickly lifted one of its arms (it can have as many as 21) and began tickling the tiny tubular feet of its prey. Instantly, the starfish retracted them, effectively immobilizing itself. Then, after only a few minutes of joint effort, the two-inch-long shrimps succeeded in toppling the large (more than a foot across) crown-of-thorns onto its back, even though it weighed 100 times as much as they. Dancing across the soft underbelly of the helpless starfish, the shrimps forced the withdrawal of the starfish's remaining exposed feet. Finally, the shrimps moved in for the kill, puncturing its tissue with their sharp pincers and tearing out large chunks of flesh from the wound. After a full day's feeding, they had reduced the crown-of-thorns to nothing more than a pile of jellied debris.

The efficient dispatch of the starfish convinced Wickler and the Talbots that the painted shrimp, in sufficient numbers, might quickly bring the crown-of-thorns under control and end the threat to Pacific reefs. Although the shrimp are not common around Australia's Great Barrier Reef and other threatened areas, they could be mass-produced in laboratories and set free in the ocean; a single female, laying between 100 and 200 eggs at a time, can theoretically produce a new generation of adult shrimps every 18 days.

In contrast, other methods of containing the crown-of-thorns seem hopelessly inadequate. Divers have already injected thousands of the creatures off Pacific reefs with lethal solutions of formaldehyde, but the population continues to explode. Indeed, Australian scientists recently reported that the starfish have so seriously damaged the Great Barrier Reef that it will take at least 20 years to recover.

Sudden Proliferation. For all the promise of the painted shrimp, scientists will take a cautious approach to this new form of biological control. They are fully aware that a sudden proliferation of painted shrimp might upset other balances in nature and, in the long run, cause more harm than good. What will the shrimp eat, for example, after they have disposed of most of the starfish? Says Lee Talbot: "We want to be awfully sure of what they are going to do to the rest of the environment before we turn them loose."

* A film of the battle at Munich's Max Planck Institute for Behavioral Physiology will be shown during the NBC special The Great Barrier Reef Friday evening, May 22, 7:30 p.m., E.D.T.

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