— This may not be at the top of your worry list, but have you ever wondered how the Hulk can stretch into a green monster twice his normal size without ripping his body to pieces? Probably not, but if you do, you might want to take a close look at sea cucumbers.
That's right. Sea cucumbers.
The makers of the movie were worried enough about that little problem to consult Greg Szulgit, assistant professor of biology at Ohio's Hiram College, who has been up close and personal with a lot of sea cucumbers.
These critters are echinoderms, members of a group of spiny-skinned animals that also includes starfishes and sea urchins, and they possess a talent that would be the envy of David Banner, the fictional mad scientist and father of the Hulk, star of a recent movie about a green monster who jumps around and beats up people.
Szulgit stumbled across sea cucumbers while doing graduate study with biologist Robert E. Shadwick at the Scripps Institution of Oceanography in La Jolla, Calif.
Sea cucumbers, like all echinoderms "can do this interesting thing with their connective tissues," Szulgit says. "Their connective tissues are very similar to ours, even on the molecular scale. They are really just about the same biologically."
But they can do something we can't do. Sea cucumbers can stretch, increasing their size without destroying tissue, and then shrink back to their normal size.
That, of course, is what the Hulk needs to do in order to fulfill his destiny. And that's why the science adviser to the movie producer ringed up Szulgit and asked for a little help. Szulgit and Shadwick had published some of their findings in the Journal of Experimental Biology, establishing them as the leading authorities on sea cucumbers and their remarkable talent.
The adviser wanted to know how the sea cucumber does its magic.
Szulgit, of course, wasn't really thinking about the Hulk when he got into studying sea cucumbers. He was interested in these ugly little animals because they could help in the development of medical treatment for several serious human problems ranging from sports injuries to debilitating diseases in which human tissues fall apart for reasons that are not yet understood.
The two researchers found that sea cucumbers and other echinoderms can stretch their bodies because the protein in their fibers, called collagen, is not fixed in their connective tissues, as it is in humans, but can slide back and forth.
"Our connective tissues look like a bunch of rope-like molecules that are all strung together," Szulgit says. "Theirs can slide past each other and they can lock and unlock."
As an analogy, he describes the process this way.
"I take my fingers and interlock them, and then I sort of let them slide past each other and you can see how one finger slides past the other. They can lock so they are unable to slide, and then they can unlock and slide back and forth.
"It's really neat. We are unable to do that, but it turns out that by looking at how these things are able to do this we're getting a really decent idea of the basic structure of our own connective tissues."
Research for Disease, Not Hulk
So the lowly sea cucumber, which Szulgit describes as looking "like a little turd," is providing a "back door into some really basic medical research that's turning out to be pretty exciting."