This is the ninth in a series of posts by Associate Curator of Invertebrate Zoology Janet R. Voight as she heads out on an expedition to Norway. There, she and colleagues will look for a wood-boring clam, Xylophaga dorsalis, to study its, well, poo. Read the first post and stay tuned for upcoming posts to find out what they discover.
My fellow researcher, Reuben, and I have been scouring the Norwegian coast for driftwood with boring clams. After four days, we had gathered a nice bunch of wood that we thought was likely to have shipworms, or even—just maybe—our target species, Xylophaga dorsalis. The issue is, of course, how to find out if they do. We’re at a field station where there are no X-ray machines or CT scanners, so we have to do it the traditional way: pick up our woodworking tools. For the last two days, we have been using chisels and hammers to split the wood apart lengthwise to see what, if anything, might be inside. Sounds simple, doesn’t it? The right tools, well-applied, should make the wood pop apart, especially if the clams have done some work for us and bored into the wood. The truth, as in so many things in life, is far different.
One piece of wood, admittedly far taller than Reuben, took us seven hours one day and three hours the next day to take apart. The work is slow and careful. We’re also looking for shipworms, Reuben’s specialty. These bivalves line their boreholes with a thin layer that forms a calcium-rich wall, so we want to get them out intact. At the tip of the siphon are hard little structures called pallets that are currently believed to be the only way to identify the animals. The shell and features of the siphon do not actually help identify the specimens, despite being most of the animal. So when you open the length of wood and encounter part of a siphon, you have to follow it to its tip to figure out what it is.
Unlike the clams I study, shipworms don’t move in straight lines. They somehow sense when they are nearing the edge of the wood or when another shipworm is dead ahead (despite being separated from them by solid wood), and they change course—maybe 90 degrees or even 180 degrees. You would think that they could follow the grain of the wood from one end to the other but they don’t, even if they are all alone in the wood. They run an obstacle course with barriers that are invisible (to us), traveling up a bit, over a bit, and around another shipworm. They avoid touching each other, but to someone who opens the wood from the side, it seems a total, random mess! We sorted them out, one by one—kind of like following one piece of spaghetti in a plate of pasta.
So far, we have two species and about 20 specimens after 10 hours of labor by two wood-boring specialists. (At times like this, I ask myself: Why didn’t I pick something else to be an expert in, like lichens that grow on everything, including car doors?!) One special surprise after all that work was one complete, though empty, shell of Xylophaga dorsalis. It’s about half the size I’d like to see, and it looked as if it had only recently died. Our efforts show that perseverance pays off. Though the numbers may seem low, we’re studying material that no one else does—isn’t that what you expect from The Field Museum?
Read on in Part 10: Searching for Sunken Treasure in the Fjords of Norway
Funding for this project was provided by the Robert A. Pritzker Center for Meteoritics and Polar Studies established by a grant from the Tawani Foundation.