Friday, June 25, 2010
It has been a while since I have posted anything in this blog, but I must admit that school has kept me very busy. After Junction, I went back to Chihuahua. I had a good time, even though it lasted too little. I have been taking microbiology and organic evolution at Tech this summer and have been able to acquire some knowledge over what was done at Junction in my mammalogy class. Those samples that we gathered are used in research on disease, evolutionary processes, and even animal characteristics themselves. How can we study disease from animals gathered in the field? This is a very interesting process that covers many aspects of biology. Epidemiology, ecology, evolutionary sciences, and even biotechnology are tools that us scientists can utilize in order to acquire data that we can use to treat, prevent, and even understand pathogenic disorders. By acquiring the tissues, one can identify organisms that serve as carriers of disease, which can be spread to humans. Below I will explain the process to acquiring these samples, preserving the skins and skulls of the animal. As a model I will be using a Peromyscus pectoralis. This is a common deer mouse found throughout much of the American continent.
As I had said in earlier entries, the rodents are collected in the field via the use of live traps (in our case Sherman Traps). Once collected, the mouse is brought to the lab where it is paralyzed. We collect blood form the eye socket through the use of capillaries while the mouse is still alive. After the animal is sacrificed, it is usually frozen and set a aside until one is ready to prepare the specimen.
When the specimen is ready to be prepared, one acquires measurements of the animals total body length, tail length, fore foot length, and ear length. If you are working with a bat, you will also measure its tragus (a small structure in front of the ear). Also, one needs to acquire the weight of the animal. Once these measurements are taken and annotated, you are ready to begin the skin removal.
You begin to remove the skin by creating a delicate incision within the abdomen, being careful not to puncture the abdominal cavity. You begin by removing the legs first to the feet, where you would cut the tibula and fibula at the base where it meets the foot. Then you remove the tail, being careful to first cut off all muscle, urethra, and large intestine. You pull the tail by grabbing the buttocks with one hand and the skin at the base of the tail with the other. You continue to remove the skin throughout the body which is easy until you come to the arms. The arms are easily removed if you pretend that you are taking off a “sweater” then cutting off at the base of the hand where it meets the ulna and radius. The head is a little tricky to skin since there is a lot of connective tissue, but if you cut it with scissors at base of skull you should be able to remove your skin without damaging it.
Once you have skinned your mouse, you want to rub the skin in corn meal. This will absorb most of the fat and moisture that can damage the look of your skin. You continue to remove the organs from the carcass. The heart, kidney, lungs, liver, spleen, and a piece of muscle are collected in order to perform DNA studies or any other that are needed. The samples are stored in liquid nitrogen in order to preserve the delicate RNA which begins to degrade immediately after the animal dies. When the carcass is empty, you can wrap it in string and dry it. It will later be exposed to flesh eating beetles that will clean it of all flesh.
The skin is then filled with cotton and wires and sown shut. When you prepare the skin, you want to make it look real. The specimen is likely to last up to 200 years, and you want to make it look its best for future scientist to study.
An evolutionary scientist can utilize your sample in order to acquire clues when building phylogenic trees. These are hypothetical depictions of the evolutionary processes. These trees have a lot of purposes since they can be utilized in many ways to answer many questions. The great thing about this process of specimen collection is that it allows one to explore both biology and natural history. One acquires a small representation of the species available in an area at a certain time. If you are interested in this, you can visit the Texas Tech Museum in Lubbock, TX. They currently present an exhibit regarding this process. I myself have 10 specimens stored within the museum that I was allowed to prepare in Junction. Although one is not allowed to freely experience the mammal and ornithology collections, the museum allows the public to view a few specimens within the museums exhibits. Above all, knowing that an individual will be utilizing your work for research in nearly 200 years makes you feel that the hard work was worth it.