Of all the creatures in the animal kingdom, the sea lamprey is not among the most attractive, or the most pleasant. Referred to by some as “nature’s vampires,” it’s a long and parasitic eel-like fish that attaches itself to the side of larger fish, essentially sucking the innards out of its host.
Now an award-winning PhD student in Biological Sciences has made an important discovery about how the lamprey processes olfactory information, which he says may help aid efforts to eradicate the invasive species from the Great Lakes.
“If we could design the ultimate cocktail of odours, we might be able to improve pheromone-based trapping strategies,” said Warren Green, who received the first place prize for the best oral presentation at the 10th International Congress on the Biology of Fish held last month in Madison, Wisconsin.
Sea lampreys found their way into the Great Lakes during the early part of the 20th century through artificial canals, and they prey on many species of commercial value such as lake trout. Authorities try to control their spread with toxicants called lampricides, which kill their larvae without harming other aquatic species.
Green, who earned his undergraduate degree from Nipissing University in North Bay and a Master’s degree from McMaster University, studies the brain functioning of lampreys, focusing specifically on the olfactory bulb, where odours are processed. He was following up on research conducted by Barbara Zielinski, his academic supervisor, which mapped out the neural route between a sea lamprey’s nose and its spinal cord, explaining why certain smells make the creature automatically swim and confirming that its brain can translate smell in to locomotion.
All of that processing happens in the olfactory bulbs of the lamprey’s brain, and Green wanted to know more.
“What were the properties of the olfactory bulb that were driving that mechanism?” he asked. “Are there specific physiological properties of the olfactory bulb that drive the locomotor response?”
He conducted a series of experiments and traced the precise region of the lamprey’s brain where pheromones, which help fish make mating and migratory decisions, and amino acids, which determine feeding decisions, are all processed. As in other fish, the lamprey olfactory bulb is “chemotopically organized,” meaning different areas of the brain process different types of odour information. However in lamprey, this chemotopy includes a specific medial region that processes information from many odours, and stimulates movement.
“That’s rare in nature,” said Green, who was awarded the NSERC Alexander Graham Bell Canada Graduate Scholarship several years ago. “Other fish have different regions of the bulb that are responsive to particular types of odours, not a single region responsive to a variety of odour types.”
Dr. Zielinski said her student did a tremendous job explaining the process in Wisconsin.
“He did a great talk, she said. “He summarized a very complex phenomenon really well. This is quite a large event and is attended by fish biologists from all over the world. It’s great that one of our students received this kind of international recognition.”
Green, who expects to defend his thesis this fall, said he hopes the work will enhance current strategies being used to get rid of lampreys. By better understanding how the process works, methods can be developed to use specific pheromones that might lure large numbers of lampreys into traps, he said.
“In order to do that, we needed to understand olfactory processing,” he said.