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Dogfish Science Lab

Guest post by Upper School science teacher Jennifer DesRochers

Ms. DesRochers gives a dogfish shark to a student.

Dissections are something that make most people go “Yuck!”. When I was in high school, our biology teacher had us dissect a worm and a frog. I was fine with the worm, having gone fishing many times, but I could not bring myself to cut into an organism that I used to catch in puddles in my backyard. Dissections have raised a lot of ethical questions- is it right to euthanize organisms so we can study their internal organs? Do they suffer or feel pain during this process? Is there a better way to study internal anatomy? Though I could spend a lot of time debating the ethics, the simple truth is that students get the clearest pictures of internal anatomy when they are actually looking at an organism and seeing where all the organs fit inside the body cavity. In this anatomy class, students dissected a sheep brain to look at the neuron organization, and then a frog, shark, and pig. The goal was to compare organs and organ systems across taxonomic classifications- an amphibian, a cartilaginous fish, and a mammal. Here are what students had to say about the dissections:

Two students begin dissecting their dogfish.

“In the past few weeks, our anatomy class has dissected a frog, a dogfish, and a pig. Although these organisms are classified differently, they have many similarities. A frog is an amphibian and spends part of its time in water and other times on land, while a shark spends all its time in the water. The pig’s anatomy is the closest to that of humans. I found it cool that sharks had 2 slits as a nose (Rostrum). I found it interesting that shark’s intestines were spiral compared to that of pigs and humans, which are coiled. Doing these dissections gave me a better sense of the location of all the different organs within the bodies. I was also surprised to find that the livers were so big compared to the stomach that were a lot smaller than I had expected. The small intestines also did not seem “small” to me. Overall doing these dissections was beneficial to me because I learned how to actually cut open organisms and learned to locate different organs.”
~Jon H.

“Although the dissections put me out of my comfort zone, I learned a lot from them. I never truly pictured or imagined opening up an organism to look inside. I didn’t realize how large the liver was either. I pictured it to be a small, non central organ, but it is a large part that is very central. I thought it was extremely interesting when we opened up the stomach and were able to see the food the animal was digesting at the time they were euthanized. My group found a hook in our shark.”
~Joanna G.

Students dissecting a dogfish

“All the dissections were very interesting to me because all of these organisms fall into vastly different classifications. Sharks are extremely different from the other we studied because they spend their entire life in the water. As a result, sharks do not have lungs. However, they use oxygen through the gills. As water flows over the gills the oxygen diffuses and is dispersed directly to the heart. Additionally, they have a compact body cavity which explains why they have a spiral intestine. The most interesting thing that I learned was about how a shark’s liver occupies almost all of its body cavity. The liver is immense because it has to accommodate a lot of oil which keeps the shark buoyant in the water.”
~Vanessa L.

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