How Do They Do That?
As the new biology research technician here at Virginia Museum of Natural History, I thought it would be appropriate to make my first post about what I do at the museum. I help out in three different departments: Archaeology, Mammalogy, and Recent Invertebrates. Two of these departments, Mammalogy and Archaeology, have skeletons in their collections. One of my tasks here at VMNH is to help prepare specimens that will end up in the collections as skeletons.
In this post, I will take you through what I do for specimens that are prepped as skeletons for the Mammalogy department. Stay tuned for a future post that talks about the process that a specimen goes through to become a skeleton for the Archaeology department. The process for the two departments is different because they are being used for different purposes.
The majority of the specimens that I prepare are salvaged from road kills. This specimen was a road kill that happened right in front of a curator’s house. It is a Virginia opossum, Didelphis virginiana. This opossum is in pretty good condition considering it was hit by a car, however, it was in the freezer for a while so it does have some freezer burn on its feet and nose thus making the skin unsuitable for a study skin to be made out of it (I’ll post about study skins in the future too).
The first thing that I need to do to get a skeleton out of this specimen is to skin it. Since I am not worried about saving the skin for a study skin, the process takes a little less time as I don’t need to be as careful about making nicks in the skin or of making too long of an incision or too many incisions. Once the animal is skinned and I have removed all the organs, I am ready for the next step.
Now the specimen is dried similar to how jerky is made (low humidity, warm temperature) and is ready to be added to the colony of bugs that will remove all the flesh off the skeleton. The drying of the specimen reduces the chances of mold developing and allows us to better control the humidity in the tank of beetles.
The hide beetle or dermestid, Dermestes maculates, is a species of beetle that is commonly found on carcasses out in nature. They eat flesh, fresh or rotten, while leaving the bones and skin mostly alone. Colonies of these beetles are commonly maintained in museums as a cheap, effective, and chemical-free way to clean flesh off skeletons. They do a wonderful job getting every piece of flesh in all the tiny spaces because the larva at hatching are extremely small. Depending on the size of the colony and the size of the specimen that is being cleaned, the skeleton can be ready in just days to a few months.
I added the opossum to a very active colony of dermestids on Friday, October 31, 2014. As you can see from the picture, there is a lot of flesh on the skeleton. My initial thoughts were that it would take them about two weeks to clean the skeleton.
As of November 4, 2014, I moved the opossum a little and put some of the legs in separate containers so that the small pieces of bone that make up the wrist and paws will not be lost in the bottom of the aquarium but will stay in the yellow containers where I can more easily find them.
As of November 6, 2014, you can see they have really been active and a significant amount of the skeleton is now exposed.
My initial predication of two weeks was actually a little long, as I ended up pulling the skeleton out Monday, November 10, 2014. This means in just a week and a half, they had cleaned all the flesh off of the bones and were even eating the cartilage that holds the bones together causing the skeleton to disarticulate or come apart. Usually the skeleton gets removed before too much disarticulation happens so that the very small bones that make up the wrist and hands are easy to find. As you can see from the pictures below the wrist and finger bones of the front feet were still articulated but the back feet were reduced to tiny bones. I believe I was able to find all of them in the bug colony but am not entirely sure. Our dermestids are wonderful, hard workers!