CALIFORNIA (31 Oct 2004) -- Like so many other wonders, it turns out that Mother Nature also invented the harpoon. After close study of a small ocean creature called the cone snail, scientists in California find that it quickly shoots a spear-like weapon, loaded with a paralyzing poison, into the flesh of its hapless prey. Then it's dinnertime. According to biologists working at Stanford University's Hopkins Marine Station in California, the snail's harpoon carries toxins that can paralyze a fish in less than one-tenth of a second. It uses one of the fastest prey-capture mechanisms yet known, they said. The harpoon itself is actually a tooth that sits retracted inside the snail's proboscis, like a poisoned arrow loaded into a crossbow. The nose-like appendage pokes around until it locates a suitable meal, then it apparently uses a pressurized fluid to fire the tooth -- its harpoon -- directly into the victim. According to Joseph Schulz, a faculty member at Occidental College near Los Angeles, study of the cone snail began because "I've been interested for a long time in these animals and how they evolved. And I'd noticed something most unusual about their prey-capture mechanism." Most unusual were the cone snail's spear, the spear's speed, its means of propulsion and the ultra-potent poisons the harpoon delivers. Useful in medicine The toxins used by the huge family of marine cone snails -- there are more than 600 species known, all living in tropical waters -- have been a scientific curiosity for years. They are extraordinarily powerful poisons, and "they are completely novel. Each species seems to have its own toxin," Schulz said. The toxins are now turning out to be useful in medicine. Neurobiologist Stefan McDonough, a staff scientist at the large biotechnology firm Amgen Inc. in Thousand Oaks, Calif., studies such toxins and explained they tend to be complex mixtures of many biochemicals called peptides. Some have been shown to have analgesic properties that can alleviate pain, and one is effective against morphine-resistant pain in AIDS and cancer patients, he said. A new toxin-derived drug called Prialt is being developed by an Irish pharmaceutical firm, Elan. Beyond that, McDonough said, cone snails "are interesting in their own right just because of their biology." Scientists are eager to learn how "this predator has evolved an incredible variety of components in its venom; there are hundreds of active components" in any given sample. Schulz said a synthetic component of one cone snail toxin is set to enter the market in January, exploiting its ability to alleviate chronic back pain. | | A Goldfish is the bait used by Jean-Paul Bingham to lure a salt-water snail into using its harpoon, orange extension from the snail at right, shown here in his lab at Clarkson University in Potsdam. McDonough said such treatments may be an important step forward in pain control, although he doesn't expect it will offer a complete answer. One problem is that the toxin peptides cannot be taken orally; they must be injected. Folding, gulping The newest results from studying the cone snail's prey-catching apparatus were reported by Schulz and his colleagues, Alex Norton and William Gilly, this fall in the Biological Bulletin, a publication of the Woods Hole Marine Biology Laboratory in Massachusetts. These scientists focused on one snail species known as Conus catus and used high-technology underwater observation techniques to record what happens as the snail shoots its poisoned tooth into small fish. The prey is immediately paralyzed, and then the snail folds the fish in half and gulps it down. This hunting technique seems to rely mostly on "great tactile response," meaning the nose's sensitive touching and feeling ability, although the cone snail "does have very simple eyes," Schulz said. A cone snail has a bunch of arrows, each ready to replace the weapon used to capture a fish. It seems the animal is continually making new harpoons, so it stays well-armed. Although the snails do not prey on humans, Schulz said there have been reports of people in tropical Pacific regions being killed by cone snail jabs. The most dangerous seems to be a species called Conus geographus, which sometimes people "inadvertently pick up, and get stung. It has a light shell," Schulz said, "and may use it [the poisoned arrow] to protect itself from being crushed." Some species are as small as 1.5 inches across. Bigger varieties may measure 4 or 5 inches across. As the name suggests, the snails' spiral shells grow into a cone shape, and in some instances they can exhibit brilliant colors. The coloration makes them popular with collectors, even though the live snails can be extraordinarily dangerous. SOURCE - News-Press |
