Caiman latirostris — a crocodile
Some of our specimens, recently discussed in our post about specimens as snapshots in time, take on a unique role after entering the museum's collections. Certain reptiles, amphibians and fishes undergo a process called clearing and staining, which helps scientists look into the critters.
After being turned translucent by a digestive enzyme called Trypsin (found in the bellies of many vertebrates including us), dyes are added. Bones and hard tissue are stained red with a chemical called Alizarin, and soft tissues are highlighted by adding Alcian blue.
The contrasting colors help scientists study the morphology - the skeletal and skin structures - of an animal. As an example, they prove especially useful for studying frog skulls, which undergo a peculiar dance of morphological change as frogs mature.
The word “fossil” often conjures images of Tyrannosaurus rex skulls, mammoth femurs, or other large bones. But those aren’t the only ones that survive through the millennia, and certainly aren’t the only ones that have importance.
KU Biodiversity Institute graduate students Sarah Spears and Kathryn Mickle study prehistoric fishes. Their fossils are so small that, in order to get them ready for study, Sarah and Kathryn have to use tiny tools to remove excess rock. Sometimes, even metal tools are too rough and inexact, so they switch over to porcupine quills — just sharp and flexible enough to clean tiny fish bones.
Like any good ichthyologist, I keep saltwater fish. When I lost a Banggai cardinalfish recently, how did I deal with this tragedy? Not by flushing it or starting a pet cemetery, but by turning that loss into a gain for the Biodiversity Institute's Ichthyology collection.
It is true that aquarium fish make less than ideal specimens. It is impossible to get accurate, reliable information on the natural habitat, behavior, distribution, and population structure of such a specimen. However, for large-scale genetic studies, a specimen without such data can still provide valuable insight into the evolutionary relationships among fish species. Likewise, we can gain important morphological information to further inform our ideas on the evolution of structures like jaws and tails.
So how does a fish reach scientific immortality after passing on to the great aquarium in the sky? First, and not surprisingly, it's important to get the fish into the freezer as soon as possible to keep it from decomposing (genetic material starts to break down quickly as the fish decomposes). When we are ready to process the fish, we first take photos of it, since preservation often causes bright colors and patterns to fade. Then a small piece of muscle is taken from one side and added to our tissue collection--this leaves the other side of the fish intact for morphological studies. We then inject the fish with formalin and store it in alcohol, or clear and stain it.
While at first blush this may seem perverse, my cardinalfish now lives on as frozen tissue and fluid specimens, where it will provide valuable genetic and morphological information for researchers and students. I know I would much prefer that to being flushed.