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This is the story of two UNC scientists, Niels Lindquist and Mark Hay, who set out to study sea squirts and wound up peddling sunscreen. The moral is: you just can't tell what benefits may result from scientific research.
Lindquist and Hay are ecologists at the UNC Institute for Marine Sciences in Morehead City. They share an interest in how soft-bodied sea creatures manage to avoid being eaten. In many cases, the defenses of these animals include toxic chemicals which make them unattractive to potential predators. (Chemical defenses are common on both land and sea: millipedes store cyanide poison in their bodies, and monarch butterflies use their bright colors to advertise how unappetizing they are.)
In the course of their research, Lindquist and Hay became interested in a animal named Tridentata marginata. These tiny creatures are sea squirts. Unless you are a biology teacher, you may have missed out on sea squirts. They are distant relatives of the vertebrates, belonging to the group called urochordates. Shaped like walnuts, or sometimes like vases, they live attached to a surface. They have two small protruding spouts, from which they will squirt water when disturbed, thus justifying their name. Sea squirts are quite common on the rocky coast of New England and much less common on the sandy shores of the Carolinas.
Sea squirts have no physical defense against predators: they cannot run away like fish and have no armor like clams. It seems obvious they must use chemical defenses. However, that's not really our story.
One day it occurred to the two UNC researchers that these particular sea squirts have another problem. Most sea squirts live underwater, typically anchored to rocks on the bottom. Tridentata marginata lives on the sargasso seaweed drifting on the surface of the Sargasso Sea. The Sargasso Sea, a vast area in the middle of the North Atlantic Ocean east of Bermuda, lies under the Bermuda High, an almost-permanent feature of the weather map. Winds blow clockwise around the high, as the do around all high-pressure centers, but over the Sargasso Sea, under the center of the high, there is generally very little wind at all. Sailors fear and avoid this area, where ships can be becalmed for weeks.
In the calm, warm waters of the Sargasso Sea float huge quantities of a sargasso seaweed, or gulfweed, as it is often called in English. Sargasso is a Portuguese word meaning "grape-bearing": early explorers gave the seaweed this name because it grows grape-sized air bladders along its fronds. Sometimes storms passing along the edges of the Sargasso Sea blow the seaweed out into more active waters. When the wind blows from the east or southeast, it often brings gulfweed up on the beaches of North Carolina.
All kinds of tiny sea animals have adapted to life attached to the floating sargasso, among them the sea squirts Tridentata marginata. Since the seaweed is floating, animals living on it are exposed to brilliant sunshine. Like us, they must protect themselves somehow from the sun's ultraviolet radiation. This is not a problem for hard-bodied animals like crabs or armored animals like barnacles, because their shells or external skeletons protect them. But how does a soft-bodied animal like a sea squirt avoid getting sunburned?
Lindquist and Hay realized that the sea squirts must produce a sunscreen. In fact, they discovered that Tridentata marginata protects itself with a natural sunscreen more effective than any sunscreen sold at your neighborhood pharmacy. They have named this previously-unknown chemical tridentol.
Tridentol protects against the powerful ultraviolet-A radiation that causes sunburn. Unlike commercial sunscreens, it also protects against the weaker rays of ultraviolet-B. Ultraviolet-B does not cause sunburn, but many doctors believe exposure to ultraviolet-B raises the risk of skin cancers.
Before we can smear tridentol over own bodies, though, there are plenty of problems to solve. The sea squirts know how to make the chemical, and we don't. Right now, a tridentol sunscreen would be prohibitively expensive. So there won't be any Tarheel Tanstopper on your pharmacist's shelf any time soon. But perhaps there will be one day.
One of the arguments for preserving endangered species is that you never know what useful things might arise from studying those creatures. Tridentata marginata is not at all endangered, as long as gulfweed floats in the Atlantic, but its unique abilities remind us how little we understand and appreciate the natural world and how much we still have to learn about it.
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Posted September 2, 1997. Features remain online as long as they remain current; they may be updated if new information becomes available.
Copyright © 1997, Center for Mathematics and Science Education. Teachers have permission to duplicate this page for use in teaching their own classes. All other rights reserved. You are welcome to link to this page, but do not copy its contents.
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