Getting the “Inside” Scoop about Fish

The museum has a new exhibition coming in January, X-rays of Arctic Fishes. Now, if you think X-Rays belong only in a hospital, think again. Fish expert Noel Alfonso describes how and why the museum uses this amazing technique to study fish and other vertebrates.

X-rays provide a unique window into the internal structure of a variety of natural history objects. I do the non-mineralogy X-rays at the museum and have X-rayed specimens as diverse as dinosaur jawbones, turtles, fossil bird bones and, of course, a wide variety of fishes. After all, my main job is that of an ichthyologist, or someone who studies fishes.

Noel Alfonso examines a fish in a jar from the museum’s collections.

Noel Alfonso examines a jar from the museum’s fish collection that contains a Blackfin waryfish (Scopelosaurus lepidus) collected in Davis Strait, Nunavut. Image: Roger Bull © Canadian Museum of Nature.

Taking an X-ray (or a radiograph, as it is sometimes called) provides a fast, easy, non-destructive way of getting information that could otherwise require time-consuming and laborious dissection. For example, if you need to know how many vertebrae a particular fish has, you can get that information in under five minutes with an X-ray.

I have also prepared X-rays of some turtles as part of a project to see what the average number of eggs was for that species. Imagine the work involved in dissecting 20 turtles! It is even possible to X-ray live turtles.

X-ray of an Atlantic Halibut.

X-ray of an Atlantic halibut (Hippoglossus hippoglossus) collected in 1962 (catalogue number: CMNFI 1964-0033). Image: Roger Bull © Canadian Museum of Nature.

The information from X-rays is very important to a natural history museum’s basic role of taxonomic and systematic research. For fishes, the number of vertebrae are important in differentiating one species from another. Often it’s easier to count fin rays on an X-ray than on the actual specimen.

With fishes, osteology (the study of bones) is more challenging than in other vertebrates because fish skeletons have many more bones. For example, human skulls have 28 bones, whereas fishes have more than 150! A lot of fish classification is based on osteology, so you can understand the importance of X-rays to this work.

X-ray with three Acadian Redfish (Sebastes fasciatus).

X-ray of three Acadian Redfish (Sebastes fasciatus), collected in Passamaquoddy Bay, New Brunswick in 1960 (catalogue number: CMNFI 1964-0485). This will be shown in the exhibition, X-rays of Arctic Fishes. Image: Roger Bull © Canadian Museum of Nature.

You can also get ecological information from X-rays. In this image, it’s possible to tell the taxonomic family and, in some cases, the genus of the shells in this fish’s stomach.

There is also an artistic element to X-rays. Some X-ray images are quite beautiful. There’s something about being able to see part of the outside as well as the inside of an object at the same time that is thought-provoking and stunning.

X-ray of the front half of a flatfish (Samaris cristatus) that shows snails in its stomach.

This X-ray of a flatfish (Samaris cristatus), shows whole snails in its stomach. The X-ray was taken for Noel Alfonso’s research on flatfishes. Image: Noel Alfonso © Canadian Museum of Nature.

I am combining my fascination with fishes, my experience taking X-rays and my involvement in an upcoming book (Arctic Marine Fishes of Canada) for an exhibition that will open at the museum in January. It’s called X-rays of Arctic Fishes.

Noel Alfonso and Susan Swan crouch behind a large table upon which rests numerous jars with fish in them.

Noel Alfonso and Susan Swan from the museum’s exhibitions team examine fish from the museum’s collections. These were X-rayed for the upcoming exhibition. Image: Roger Bull © Canadian Museum of Nature.

To prepare for this show, my colleague Roger Bull and I spent three days at the Royal Ontario Museum in Toronto in early November. We used their X-ray system to prepare radiographs of Arctic marine fishes for the exhibit. The system generates very large, high resolution files that will be used to print transparencies backlit in light boxes.

Noel Alfonso stands in front of an X-ray machine that has the front door open in order to place a specimen.

Noel Alfonso puts some fish specimens in the X-ray machine. Image: Roger Bull © Canadian Museum of Nature.

This exhibition will highlight the spectacular osteological architecture of fishes and showcase some of the fascinating species found in the Canadian Arctic. It will also highlight the fact that our museum has one of the best collection of Arctic marine fishes in the world. We are hopeful that this show will be an attention-grabber that will have wide appeal.

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