The beauty of fish bones

An x-ray of Carangoides gibber, commonly known as the imposter trevally, a small tropical fish.IMAGE: KYLE LUCKENBILL, ANSP Sandwiched between two floors of dead fish at Philadelphia's Academy of Natural Sciences, Kyle Luckenbill is creating art. As the Academy's curatorial assistant resident dead fish paparazzo he photographs and x-rays the institution's 3,000 species-defining specimens as part of a National Science Foundation grant. "We didn't really plan an exhibit with the project, but it was one of those things where it was sort of a no-brainer," Luckenbill says. So far, Luckenbill has x-rayed about 500 specimens, about a dozen of which are on display in an exhibit called "All Types of Fishes," part of the museum's rotating "Art of Science" series. "Imagery like this is really created as a scientific tool, but we look at it and say, 'but gosh, it's beautiful!'," says Barbara Ceiga, vice president for public operations at the Academy. "Sometimes people who actually are producing it are like, 'you want to hang what on the wall?'" Inadvertent artistic endeavors aside, the x-ray project has identified new species and has even provided the final ruling on a world-record breaking fish caught in New Jersey. If the fish turned out to be a red hake, it counted as a world record fish, but if it were a white hake, it was just a big fish. (The red hake broke the record at 12 pounds and 13 ounces and measured 33 inches long and 19 inches around!) The "primary type" specimens, which Lukenbill x-rayed for the exhibit, are the standard-bearers for their entire species. Primary type specimens are the first members of their species to be systematically described and named in the literature, and define the telltale characteristics of the species. The Academy has about 1.5 million fish specimens in total, the majority of which are secondary types. The 3,000 primary type specimens upon which Lukenbill focuses sit in alcohol or formalin filled glass jars, and some since the 1800s. Over time, the solution degrades the samples, making their documentation and study more difficult. "They start to decalcify, the bones start to break down and it's tougher to get a really good x-ray," Luckenbill explains. "It's important to do this stuff now, because a few years down the line, there'll be nothing left and you can't get a decent x-ray." X-rays are crucial identification tools because the number of vertebrae is a defining feature of many species; for some types of fish, it's the only way to tell the difference between two closely related species. In order to preserve the primary type specimen intact, researchers can't cut them open and count their backbones. Luckenbill fishes a quarter-sized Chrysiptera punctatoperculare, collected in 1946, out of a jar the size of a salt shaker. He delicately wipes the excess alcohol off on a towel browned by fish goo. The tiny fish is propped up on a cloud of fluffy white polyfill before he leaves it on the exam table. A few clicks from the other side of the lead door, and the fish is bombarded by x-rays, its image captured by one of only three digital x-ray machines of its ilk on the US East Coast. Sometimes, this process gives Luckenbill a bit of trouble, especially with the larger specimens--like the Academy's extensive eel collection. When the specimens are preserved in formalin, they become rigid. The long eel bodies are forever locked into a spiral formation, taking on the cylindrical shape of the jar. When lifted out of their jars, the eel can't be flattened out without breaking bones or destroying delicate structures. So Luckenbill meticulously snaps shots of each part of the eel and aligns them using Photoshop. The resulting images of intricate fish bones against a stark black background beg for closer inspection. "You take something you think you're familiar with and you show someone a hidden part of it, a surprising part of it, there is something really delightful about that," says Ceiga. "You think, 'I thought I knew what fish were, but I had no idea.'" Ceiga says that she can see the understanding dawning on the faces of visitors to the gallery. "As they start to look at things more closely you see the thought process of grouping things," she says. "That's learning, even though you don't feel like you are learning." The "Art of Science" series was started about 18 months ago with an exhibit of 200 year old botany drawings and pressings. The fish x-rays will be on display through the end of July, and will be followed by "A Many-Colored Glass: Ethereal Images of Microscopic Marine Life," an exhibit of colorized photomicrographs of diatoms which opens August 7.

The beauty of fish bones

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