Deep-water cutting is not an attractive fish by any conventional standard. You won’t find him hanging on a plate or getting a role in a Disney movie.
What you might say about the bottom dweller is that he is a survivor, having made a living at the bottom of Canada’s deepest, coldest lakes since the last ice age.
Researchers at T. Scarborough University are now sequencing their entire genome to see how this seemingly unremarkable fish has been able to adapt to such extreme environments.
“He’s an iconic Canadian survivor,” says Nathan Lovejoy, a professor in the biology department whose lab is doing genetic research on the sculpture thanks to a grant from the CanSeq150 initiative.
“Here’s this small, humble fish that has been able to survive in these really difficult habitats, and we don’t know much about it, especially how it has been able to adapt over time.”
Deep-water esculins live almost exclusively in lakes with depths greater than 35 meters and temperatures below 8 C. Their distribution extends from the Great Laurentian Lakes and the Gatineau region in northwestern Quebec to the more deep from Ontario, Manitoba and Saskatchewan to Great Slave and Great. Bear Lake in the Northwest Territories.
Physically he is relatively long and flat, with two small black eyes located at the top of his head. Adults are small, typically 10 to 15 cm (4-6 inches) long and weigh less than 25 g (less than an ounce).
Despite its non-exceptional appearance, it plays an important role in the Great Lakes food chain, connecting the small crustaceans and aquatic insects that feed on the lake trout and the larger predatory fish that feed on the cut. .
At the same time, Lovejoy says that because it lives at such deep depths, it is still a little-studied fish, with relatively little known about its biology and genetics.
A “glacial relic”
The closest relative of the deep-water cutter is an Arctic ocean fish found in shallow water called a four-horned sculpture. Lovejoy says the deep-water cut probably originated when the ancestral four-horn cut was pushed to land in freshwater continental habitats by the advance of glaciers. Over time they adapted to these freshwater conditions.
Alex Van Nynatten, a postdoctoral fellow in the Lovejoy lab, is currently doing the huge job of dumping heaps of data in an effort to sequence the fish’s genome.
“Deep water sculpture has undergone these important changes in his body as a result of deepening more and more,” he says. “So we really want to look at the specific molecular adaptations that this fish has undergone to adapt to these freshwater environments.”
In collaboration with Professor Belinda Chang of the Department of Cell and Systems Biology, Van Nynatten is especially interested in studying the genes of fish vision, specifically those that can be seen in cold, low-light conditions.
Over time, the deep-water cut has also lost the horns at the top of its head that are still present in the four-horn sculpture.
“It is possible that as it deepened, birds no longer preyed on them, so this defense mechanism was no longer necessary,” he says.
The fact that the fish has undergone such drastic changes in a relatively short period of time makes it a fascinating topic for a study of genetics, says Van Nynatten. Researchers would also eventually want to sequence the genome of the four-horn sculpture to compare the two species.
Despite showing remarkable success in adapting to its environment over time, the future of deep-water sculpture could be in jeopardy due to climate change and invasive species such as round gobies and zebra mussels. It is currently listed as a species of special concern under the Canadian Endangered Species Act.
In an effort to help with monitoring, Lovejoy’s lab is working with Professor Nick Mandrak on developing a technique that is based on environmental DNA analysis. Because fish spill DNA through their feces and urine, the technology could track the number of individual deep-water squirrels that live in a given area from a water sample.
“One of the big problems with climate change is that it forces everyone living in a lake more and more into cold water, so there’s a lot more competition,” Van Nynatten says.
“Having a way to control their numbers would be very beneficial, especially because they live in such deep and inaccessible environments.”
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Materials provided by the University of Toronto. Original written by Don Campbell. Note: Content can be edited by style and length.