Robyn MacLellan is a fourth-year biochemistry student completing honours research under the supervision of Suzanne Currie, who is currently on sabbatical, and Tyson MacCormack.
MacLellan’s thesis is entitled, “Elasmobranchs as models of stress: the effect of hypo-osmotic stress on the chemical and molecular chaperone systems of the spiny dogfish shark (Squalus acanthus).” MacLellan conducted most of her research for this project over the summer in the Mount Desert Island Biological Lab in Salsbury Cove, Maine.
Elasmobranchs are a subclass of cartilaginous fish that includes sharks, skates, and rays. The animal that MacLellan is focusing on for her research is the spiny dogfish shark, which falls into this subclass.
MacLellan looked at stress, specifically hypo-osmotic stress, on these sharks. MacLellan exposed specimens to an environment with seventy percent seawater. These specimens were attached with an arterial cannula (a piece of tubing surgically inserted into an artery) to draw blood without causing unnecessary stress. Blood was taken at four separate times over forty-eight hours: at time zero (before salinity dropped from one hundred percent seawater to seventy percent), time three (upon completion of salinity drop to seventy percent), time twenty-four, and time forty-eight. After all necessary blood samples were taken, the specimens were euthanized and tissues were collected for further analysis.
In the blood samples, MacLellan is looking for heat shock proteins, trimethylamine oxide (TMAO), and urea concentration. Elasmobranchs are known as osmoconformers, meaning that when they are exposed to a change in salinity, they try to cope with the new stress by conforming their internal osmotic pressure to that of the seawater. TMAO is an osmolyte that significantly contributes to the sharks’ osmotic pressure constant, and is known as a cellular protectant. MacLellan is trying to determine if, during a stressful event, the dogfish sharks dump TMAO and urea concentrations out of their cells while inducing heat shock proteins. TMAO also indirectly promotes proper protein conformation—in the face of stress, proteins can denature (an unfavourable process), and if the specimens are dumping TMAO, they are losing that protective system. If they are dumping TMAO, heat shock proteins will be induced to cope with the potential of protein denaturation.
MacLellan’s project is relevant due to its implications for climate change. Seawater is being gradually diluted due to melting polar ice caps—sea animals, now more than ever, are facing the threat of diluted seawater. Spiny dogfish sharks have been known to travel into estuaries and brackish water for breeding and to escape predators. MacLellan aims to learn how they cope with this, which could provide further insight into how other organisms could potentially cope as well.
Her research has implications for human health as well. Heat shock proteins are a highly conserved protein family, meaning they are present in most animals. By learning how animals such as elasmobranchs cope with stress, comparative studies can be completed in the future.
MacLellan explains that Currie was the reason she chose Mount Allison to pursue her studies. While still in the twelfth grade, MacLellan booked a campus tour that included the chance to talk to a professor. After meeting Currie, MacLellan was really struck by how passionate she was for teaching, her students, and her research. This experience made MacLellan realize that Mt. A was a close-knit community that was right for her.
Now that she is working for her, MacLellan says that as a supervisor, Currie is “fantastic” and is a “great resource.”
“She expects you to work independently and to learn things for yourself, but is always there when you have questions.” MacLellan says that this independent learning method works best for her.