5 Jun
Posted in: Sharks, URI
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Sharks, Skates, and Chemistry: What can they Tell Us?

Species used in the TMAO study.

Species used in the TMAO study.

URI grad student Abigail Bockus draws blood from a spiny dogfish.

URI grad student Abigail Bockus draws blood from a spiny dogfish.

Could sharks and skates play a role in our understanding of climate change impacts? What role might they play in helping people choose only fresh food? Or could these fish actually help scientists develop drought resistant crops? These are the kinds of questions URI Graduate student Abigail Bockus wonders about. And that is why, at the moment, she is using one hand to hold down a four-foot spiny dogfish shark while the other holds a needle that will draw blood.

Sharks and skates contain a cellular molecule known as trimethylamine oxide, or TMAO. In sharks, the molecule helps regulate water content, buoyancy, and changes the temperature at which body fluids would normally freeze. And while many scientists are currently evaluating other possible uses for TMAO, Bockus is attempting to find out just where the protein comes from in the first place.

“We know that sharks typically have TMAO in their systems,” Bockus explains. “We also know that a certain amount of it comes from the foods they eat, which also contain the protein. But just how much comes from foods and how much does the animal manufacture itself? There are lots of theories and disagreements about how TMAO functions, as well as how it is produced in the body. I’m hoping this research will contribute to settling some of the arguments, or at least to unifying a lot of these theories.”

But why study where a chemical in sharks comes from? Although there are no current medical or commercial uses for TMAO, it may play a key role in a variety of issues. Since this substance regulates things like water retention within the organism, there’s a chance that it could help farmers raise plants that are resistant to the drought conditions that plague them with increasing frequency. TMAO is also the substance that produces the “fishy” odor that increases as fish begin to spoil. If a way were found to measure this protein, the result may be a reduction in the incidences of food poisonings. And since TMAO is found in higher amounts in cold water sharks than warm, there is a chance that learning where the substance comes from will help predict how sharks and other organisms will react to climate change. That’s why Abigail Bockus is trying to figure out where the sharks get this chemical in the first place.

Shark species are kept in a holding tank.

Shark species are kept in a holding tank.

The building where Bockus conducts her experiments is on URI’s Bay Campus. Inside, there are several pools of water, roughly four feet deep and twelve feet across, like an oversized kiddie pool. Of course, these pools contain the stuff of kiddie nightmares: spiny dogfish, “smooth hounds”, and skates cruise in the cold shallow waters. Some of them poke their heads well out of the water as they swim, constantly on the prowl for food.

To better understand just where TMAO comes from, Bockus will hold these animals in captivity for several months. One group will be fed the normal diet of captive sharks, a combination of herring, which is high in TMAO, and squid, which contains little or nothing of the chemical. The other group will be fed squid only. As the months go by, Bockus will periodically obtain blood samples to determine whether those on the low-TMAO diet continue to maintain those protein levels despite the absence of herring in their diet. If they do, it would seem likely that some sharks are able to produce the chemical on their own, instead of it coming from food.

Today is what Bockus refers to as “time zero”. The sharks have all been fed normal food to this point. It marks the first step in her experiment, taking blood samples to determine a baseline in the amount of TMAO found in her subjects. In the months ahead, she will investigate whether there are changes in TMAO levels as their diet changes.


Marine Research Assistant Danielle Duquette assists Bockus in blood sampling.

On this day, Bockus is getting help from Marine Research Assistant Danielle Duquette. Her job will be to quickly snatch the fish from the tank and carry it to the table. There, the fish will be weighed, then immersed in a combination of salt water laced with a carefully chosen level of anesthesia.  Duquette and Bockus will hold the fish in place, gently passing the water across its gills. As the water circulates, the shark will absorb the anesthesia into its bloodstream, making the blood sampling less stressful on the fish.  Conducting the procedure on all the animals will take six hours. While the anesthesia is working its way through the animal’s system, its muscular body telegraphs periodic attempts to thrash around: seconds before it twists, the muscles tense; it’s then that Duquette needs to be certain of her grip.

Even before the first shark was captured by Bockus and others last spring, the experiment had to pass a stringent set of requirements. Since the process would involve experimenting with living creatures, Bockus had to write a proposal showing why it was essential to use them, rather than rely on other data, such as computer programs. “I had to justify the use of invertebrates,” she explains. “Every university has an ethics panel that monitors these regulations. If similar results can be obtained by using a computer, the proposal will be rejected. Only if there is no other way to obtain the results will I be allowed to experiment on animals. And the higher the intelligence level of the invertebrate, the more difficult it is to obtain permission.” These regulations have been around for some time, and are part of a strict protocol for monitoring animal experiments in universities. The board making the call on these experiments is composed of faculty members, and the process is rigorous.

The shark on the table is proof that Bockus was indeed granted permission to move ahead with her experiment. After five minutes, the spiny dogfish, now turned on its back, has stopped squirming. Bockus, wearing blue rubber gloves to protect both her hands and the fish, lowers the needle to a spot just in front of the tail. The blood draw is quick, and the samples will go into a centrifuge to separate the chemicals. The shark is returned to the tank, and Duquette gently holds the animal in the water, giving it time to begin to get its bearings before being released.

The process of blood sampling will be a long one, lasting throughout the day. Then, in another month, it will be repeated. And the month after that, and the month after that. When it’s over, there will be data to be correlated, conclusions to be drawn. It may be years before the results of Bockus’ experiment become that link in the understanding of TMAO that she spoke of earlier. But this is the nature of science: each piece of a puzzle must be recognized, understood before it is placed where it belongs in order to compose the full picture.


  • Great article!

    • Thanks! I had a lot of fun doing it!

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