Potent Ocean Poisons Could Help Fight Diseases on Land : Science: Researchers are looking at deadly compounds in algae and reef-dwelling animals as potential weapons against human ailments.

Coral reefs in the Caribbean Sea and off the coasts of North Carolina and Australia may look idyllic, but some of them hide enough poison to enliven a paperback thriller.

The toxic substances that endanger the lives of sea creatures don’t threaten humans, however. To the contrary, they may someday be used to save human lives and solve a variety of land-based problems, such as combatting insect pests.

Using ocean poisons for such purposes is a concept still under development. In one of the most active areas of research, pharmaceutical companies are looking at deadly compounds coming from algae and small, reef-dwelling animals as potential weapons against disease.

Lethal substances from certain sponges and tiny corals seem to inhibit human cancer cells. Compounds from soft corals reduce inflammation caused by arthritis and asthma. Material from sea squirts may help treat diabetes.

“Furthest along are substances that seem to fight arthritis,” said William Fenical, a chemist and oceanographer at the Scripps Institution of Oceanography in La Jolla. “We have materials that have been licensed and are going out to the pharmaceutical industry for development.”

Scientists don’t view marine organisms as a prospective panacea. “In the long run we may not be harvesting a lot of drugs from the sea,” said Mark Hay, a marine scientist at the University of North Carolina at Chapel Hill.

“Rather, we view marine life as a sort of library offering potential solutions to medical problems. What we’re looking for are magic bullets, not things that are broad toxins.

“For instance, there might be something that produces a compound that works as a good pain suppressor. We wouldn’t harvest it all from the sea. Chemical analysis would first have to prove that it could be reproduced synthetically.”

Hay, who with Fenical has led expeditions to the reefs, speculated that chemicals from sea plants and animals also might be useful as insecticides.

“Here’s a whole arsenal of materials that terrestrial insects have never seen,” he said. “So the insects have no evolutionary experience or immunity to them.”

Agrochemical companies have recognized sea-born pest-control possibilities, but have been slow to pursue them. The potential cost of synthesizing large quantities of compounds from the oceans holds them back.

“Agrochemicals have to be very cheap--a couple of bucks a pound--because you usually have to spread them over comparatively large areas,” Fenical said. “In many cases, what has been discovered in the ocean has been effective, very interesting, potentially very usable, but the economics don’t look that good.”

“Only in the past few years, through the work of Mark Hay and one or two other people worldwide, has it become abundantly clear that chemical substances are the basis of the interaction of plants and herbivorous animals on coral reefs,” Fenical said.

Before, it had never been decisively proved that some sea plants and small herbivores subject to predation specialize in chemical defenses to stay alive.

Fish that gobble anything in sight make tropical coral reefs the world’s most heavily grazed habitats. Measurements have shown that the plants, tiny animals and coral on each square yard of a reef can draw from 40,000 to 156,000 fish bites a day.

To escape this feeding frenzy, some small creatures dine on poisonous seaweed to make themselves unpalatable.

Some nonpoisonous seaweed becomes as unpalatable as possible by calcifying into concrete-hard substances, but fish still go after it. “The fish actually grind up large amounts of reef material,” said Hay, whose work has been supported by the National Geographic Society.

“It’s analogous to cows trying to graze the parking lot of a fast-food restaurant for its spilled grease.”

But for most small reef animals, poison is their defense. By dining on poison plants, one group of sea slugs has developed immunity to the toxicity, making itself so unappetizing to fish that it has been able to shed its protective shell.

Convinced that the threat of predation is the reason small, herbivorous sea creatures feed on poisonous plants, Hay suspects that the same motive guides many terrestrial insects.

So does Elizabeth Bernays, a University of Arizona entomologist. Studying caterpillars, aphids and their predators, she has found that insects choosing a specific plant for shelter or food have a much better chance of surviving than those that are less selective.

On land, poison isn’t the prime attraction. “Some insects may have been better camouflaged on one plant than another,” Bernays said. “Others might have developed some kind of odor analogous to garlic breath that turned off their predators. Then there might have been those that fed on plants that made them similar in color and taste, so as prey they weren’t noticed.”