New Research
Examining a different side of the leech
Archived article from Sep 20, 2004
Contrary to popular belief, few leeches suck human blood. Take the North American aquatic leech Thermomyzon rude (T. rude), which was named as such for its rather “rude” habit of feeding inside the nose of a duck. (If you’ve ever seen a duck sneeze, you’ve probably witnessed the work of T. rude.)
According to Daniel Shain, assistant professor of biology at the Camden campus, T. rude really isn’t rude at all. In fact, it would rather starve to death than feed off a human. Plus, T. rude is one of very few invertebrates that do not abandon its young. The beautiful cocooning butterfly? Hardly an admirable parent: It’s long gone before its offspring’s first flight. But what marvels Shain most is that T. rude’s cocoon is virtually indestructible.
Thanks to a recently awarded three-year National Science Foundation grant, Shain will conduct groundbreaking research into the unique biomaterials found in the T. rude cocoon. Unlike much of the current leech research devoted to the use of anticoagulants and other leech secretions in medicine, Shain aims to do for the leech cocoon what has been done for the spider’s web. Bridges are now being built out of spider webs, which have proven to be stronger than steel. Shain, a developmental and evolutionary biologist, says that the T. rude cocoon exhibits some amazing properties, including resiliency to harsh chemicals as well as sweltering temperatures that exceed 250° Celsius (480° Fahrenheit). Aquatic leeches, like T. rude, secrete specialized proteins that assemble underwater into a clear, membranous sheath, which becomes sealed at either end, as if glued. Within just a few hours, this process requires the synthesis of thousands of kilometers of fiber. Shain believes that, like the cocoons of the silkworm used to harvest silk, T. rude’s cocoon could also yield interesting industrial, biomedical and even astronautical applications.
Shain also will explore aspects of T. rude’s exceptional development. A single parent of T. rude (the hermaphroditic leech produces sexually with a mate, but only one parent rears its young) lies on top of the cocoon, filled with dozens of embryos, until it hatches. At one millimeter in diameter, T. rude’s embryos are hundreds of times larger than a human embryo – ideal potential, Shain says, for embryonic stem cell research. The parent leech cares for the newborns until they are juveniles (about two weeks later) and ultimately takes the youngsters to their first meal: the nose of a duck, which is what they feed on exclusively. T. rude, which has an average lifespan of one year, dies after harvesting its eggs, indicated in its turning green from translucent.
Shain’s research has taken him around the world. In the Amazon River, he used himself as leech bait, which he says is common practice for leech researchers. Although no leech bit him then, he still managed to identify two new species of leech, one of which evolved gills. “Each leech is different,” Shain says, “just like every snowflake.”
– Cathy Karmilowicz
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