Through her research, UWinnipeg professor, Dr. Sara Good, hopes she can help protect Canada’s fisheries from a devastating invasive species.
Sea lampreys are parasitic aquatic creatures that have decimated freshwater fish populations ever since they made their way into the Great Lakes in the 1920s.
We’re trying to find genes that could be targets to knockout fertility of sea lamprey.
Dr. Sara Good
“Natively, sea lamprey come into streams in Maine or New Brunswick on the East Coast,” Dr. Good explained. “They go downstream to the Atlantic Ocean and, in the Atlantic Ocean, they prey on sharks, rays, and other fish. But, since they have co-evolved, lamprey don’t typically kill their host.”
When lamprey became landlocked in the Great Lakes, they began feeding on lake trout, lake whitefish, walleye, and many other species. Because freshwater lake fish are not adapted to them and are smaller than a sea lamprey’s native prey, the lamprey typically kill the host fish.
“By the 1940s, sea lamprey were exerting a huge negative toll on freshwater fisheries in the Upper Great Lakes,” Dr. Good explained.
Efforts to control sea lamprey
This led to the formation of a binational organization, the Great Lakes Fisheries Commission (GLFC), which has established multiple mechanisms to help control the number of lampreys in the Great Lakes. For example, physical barriers help prevent the fish from migrating throughout the system and a lampricide treatment is applied every few years, which kills their larvae.
Another method is to catch male sea lampreys before they spawn upstream. These males are then treated with a chemical that makes their sperm non-viable. These sterile males are released into the spawning area, but they don’t fertilize a female’s eggs.
“This has also been an effective method for reducing the population,” Dr. Good said. “But lampreys are phenomenally prolific and still exert a reasonably heavy toll on the freshwater fisheries. There are still tens of thousands getting through the system.”
Dr. Good’s latest research aims to add a new tool to the fight to control this invasive species.
Through her research, Dr. Good hopes to identify which sea lamprey’s genes are responsible for making it male or female in order to manipulate the sex determination system.
“We’re trying to find genes that could be targets to knock out fertility of sea lamprey,” Dr. Good said. “So, rather than bringing them in and just sterilizing males, you could introduce genes that make individuals sterile in populations. That could be another mechanism to reduce the negative impact of sea lamprey in the Upper Great Lakes, but would have to be implemented very carefully.”
What we can learn from an ancient vertebrate
With funding through the Natural Sciences and Engineering Research Council of Canada (NSERC), Dr. Good also hopes to understand how the process of sex determination and differentiation in lamprey compares to that of other vertebrates.
“Geneticists, in particular, use a lot of models. And different species serve as good models for different things,” Dr. Good explained. “We use models to understand genetic pathways. A mouse is a great model for humans for many things, but not for everything. The worm, C. elegans, for example, turns out to be a great model for the nervous system.”
Dr. Good’s research uses sea lamprey as a model to better understand the hypothalamic–pituitary–gonadal (HPG) axis, which regulates reproductive activity and sexual development.
“Sea lamprey are about 100 million years older than any other living vertebrate, but they are true vertebrates,” Dr. Good said. “They’re also the oldest taxa that have the HPG axis.”
The sex hormones, estrogen and testosterone, are produced in the gonads following specific signals from the hypothalamus, pituitary, and gonad. The coordinated signaling system of the HPG system in humans regulates, among other things, the menstrual cycle in females and spermatogenesis in males.
“The HPG axis is not present in non-vertebrates. But lampreys have it,” said Dr. Good. “I’m looking at the oldest vertebrate, so I’m basically working to understand the core components, potentially, of the HPG axis system.”
The main application of Dr. Good’s research is to help control the invasive populations of sea lamprey in the Upper Great Lakes, work she is doing in collaboration with Dr. Margaret Docker (UofM) and many others working for the GLFC. But, she also hopes that in the future her research could help us better understand what impacts reproduction and fertility.
“Not just for humans,” Dr. Good concluded. “We’re having huge impacts on aquatic species. And many of the chemicals, including endocrine disruptors and other forever chemicals that are in our water systems, do impact the fertility of other species.”
