The latest exhibition at the Canadian Museum of Nature is a provocative look at the inside of animal bodies. A technique called plastination gives durable, graphic and artistic results that allow curious viewers to see and compare biological systems of many different species.

For centuries before this innovative plastination approach, scientists dissected plants and animals to compare anatomical features in an effort to answer their questions. As well as telling us about how the various animals live, the comparison of physical features is also the foundation of taxonomy—the naming and classification of species. Comparative anatomy is a primary tool of species discovery.

A room full of mounted skeletons.
Part of the skeleton collection in the Gallery of Comparative Anatomy, National Museum of Natural History, in Paris. Image: Mark Graham © Canadian Museum of Nature

The size of an anatomical feature (for example, the length of a jaw), or the number of body parts (for example, the number of spines in a fish’s fin), are part of the list of characteristics that can help to distinguish one species from another.

Sometimes, scientists have to dig much deeper to find those critical markers of identity. For example, researchers working with insects often have to dissect and study the shape of the reproductive system to establish the identity of a species. And in most cases, a full diagnosis requires a long list of characteristics.

Illustration of the bones in a human arm, dog leg, bird wing, whale flipper.
A comparison of the upper limbs of vertebrates; colours indicate similar structures for each. Image: Volkov Vladislav Petrovich © Volkov Vladislav Petrovich (licensed: CC BY-SA 4.0)

One thing that all biologists know is that nature offers a great deal of variability in all living things. To fully understand those variations for each species, an extensive collection is ideal. Such a collection is amassed across a wide range of geography and over time. A large collection provides for understandings about the variety of shapes and sizes, differences between males and females, and how a species responds to different environmental conditions.

Collage: Drawings of two fishes.
Sockeye Salmon (Oncorhynchus nerka). Left: Adult male colouration when it is living in the ocean. Right: Adult males live in freshwater when in reproductive condition, as seen here. Images: Jmabel, United States Government, and Timothy Knepp, U.S. Fish and Wildlife Service © Public domain

Recently, new tools have emerged to assist in the detailed task of identifying species. The use of genetic material such as DNA (deoxyribonucleic acid) can be fast and powerful in differentiating and comparing species. Molecular techniques are especially useful for comparing species that are closely related and difficult or impossible to separate based on just anatomical parts, or for identifying species in their larval stages before they reach the more identifiable adult stage. Because of these new methods and tools, museums are now storing tissues and genetic material for future scientific research in addition to collecting entire plants and animals.

Collage: Drawings of two plants.
Two species of Arctic grasses that are difficult to tell apart by their physical appearance alone (left: Puccinellia banksiensis; right: P. phryganodes). Museum scientists have established a DNA procedure to distinguish hundreds of Arctic plants (read the article). Images: Roger Bull © Canadian Museum of Nature

Natural history collections come together through field work and in exchanges with an extensive network of collaborators. Museums’ species-discovery programmes include the preservation and sharing of the specimens and data they collect for scientific questions now, and for centuries to come. The Canadian Museum of Nature forges scientific collaborations amongst the Alliance of Natural History Museums of Canada, with the Alliance of Natural History Museums of the Arctic, and with colleagues at universities, government labs, and other museums around the globe. As we continue our adventures in species discovery, we take a careful look at nature inside and out.

An X-ray of three fish.
An X-ray of three Arctic sculpin species. Top to bottom: Polar Sculpin (Cottunculus microps), Longhorn Sculpin (Myoxocephalus octodecemspinosis) and Fourhorn Sculpin (M. quadricornis). See this X-ray and others at the museum in Beneath the Surface: X-rays of Arctic Fish. Image: Noel Alfonso, Roger Bull © Canadian Museum of Nature