Researchers at the University of British Columbia’s Institute for the Oceans and Fisheries (IOF), the Department of Fisheries and Oceans (DFO), University of Toronto, Dalhousie University, and the Hakai Institute examined juvenile sockeye salmon from three locations along their migration route in coastal British Columbia. In 2016 and 2016, the body condition and nutritional health of juvenile sockeye was sampled in the northern Strait of Georgia, the highly tidally mixed Johnstone Strait, and Queen Charlotte Strait.

“We measured the fatty acids in the sockeye salmon tissues, specifically looking at stored fatty acids that are important for mobilizing energy during periods of starvation, such as what these salmon face in Johnstone Strait,” said lead author Dr. Jessica Garzke, an IOF postdoctoral fellow. “We found that short term changes in health differed between years but were not related to zooplankton biomass, abundance, average size, or species composition. Rather it was the quality of the zooplankton that played an important role.”

Leaving the generally productive and good foraging area of the Strait of Georgia, to the typically food-poor conditions of the Johnstone Strait has a powerful impact on the young salmon. When juvenile sockeye salmon entered Johnstone Strait in 2015, they were generally in good body and nutritional condition, and able to use stored energy resources to manage traversing this section, where prey availability was low, to get to Queen Charlotte Strait. In 2016, however, juvenile sockeye salmon entered Johnstone Strait with poor body and nutritional condition, and they struggled to regain condition when they reached Queen Charlotte Strait.

“It was clear from our study that differences in juvenile salmon condition between the two years were due to changes in the food quality available to the fish, more than any other factor. Incorporation of food quality measurements in addition to analysis of quantity of prey is vital to understanding changes in fish condition and survival between years,” Dr. Garzke said.

Understanding how diet affects the salmon’s growth and health during the early part of their lives could help researchers understand the long-term population trends of the species including their decline, says Dr. Garzke. Sockeye salmon are an iconic species in British Columbia, important both commercially and culturally, and are in decline.

The research highlighted how variable the ocean conditions are that juvenile salmon face in British Columbia, said senior author and IOF associate professor Dr. Brian Hunt, with migrating salmon experiencing “boom and bust” feeding conditions. “Importantly, feeding conditions are not consistent from one year to the next. They are impacted by changing climate, and areas that had good feeding conditions in one year can be bad the next. The more areas that switch to bad feeding conditions the tougher it is for juveniles to survive the coastal migration and their first winter at sea.”

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Disruptions to the body’s internal clock — which coordinates the timing of biochemical, physiological and behavioral processes — are associated with a range of diseases, including cancer, cardiovascular conditions and susceptibility to infections, as well as a higher risk for accidents. Common disruptions of circadian rhythms are jet lag and shift work, which is performed by some 30 million people in the U.S.

“We are studying two mutations, both of which affect our ability to respond to shifts of the light cycle,” says neurobiologist Eric Bittman, Professor Emeritus of Biology. “Both of them speed up the clock. They reveal how vulnerable we are to disruptions in the light:dark schedule.”

In mammals, circadian rhythms are generated internally by a master pacemaker in the suprachiasmatic nucleus of the hypothalamus in the brain. In addition, every cell in the body has its own circadian clock, which the master pacemaker coordinates. In the normal, light:dark and fluctuating environment, circadian clocks create 24-hour cycles. However, in constant conditions, such as when hamsters are studied in darkness, the rhythms generate cycles whose period is longer or shorter than 24 hours.

“What this reveals to us is that there’s some internal mechanism that is generating rhythmicity, and that the animals are using cues from the environment, the most powerful of which is the light:dark cycle, to sync it up to exactly 24 hours,” Bittman says.

In previous research, Bittman and team identified a recessive mutation, which they call duper, as a defect in the circadian regulator gene Cryptochrome 1 (CRY1) of Syrian hamsters. By improving the draft of the hamster genome using fast homozygosity mapping, they created a modern genetic research model for investigating human diseases.

In a follow-up paper published recently in the Proceedings of the National Academy of Sciences (PNAS), the research team focuses on the effects of duper in genetically altered hamsters. The scientists identify previously unsuspected functions of CRY1 in circadian entrainment, which is the synching of the biological clock with external signals, and heart disease.

“Duper speeds up the clock in constant conditions and it makes it be able to shift by as much as 180 degrees in response to even a brief pulse of light,” Bittman explains. “We suspect this might be relevant in understanding the effects of jet lag and shift work.”

The body’s organs reset their clocks at different rates after circadian disruption. This temporal misalignment is believed to cause the adverse health effects associated with shift work. “Almost all of our physiological processes are rhythmic,” Bittman says.

The researchers found that circadian re-entrainment is accelerated in duper mutant hamsters, independent of the speeding up of the clock. In an effort to understand more about the health consequences of circadian misalignment, the researchers examined effects of duper and phase shifts on a hamster model of heart disease known to be aggravated by phase shifts.

Simulated jet lag, in the form of eight-hour phase shifts every second week, shortened the lifespan of cardiomyopathic hamsters. However, the shortened lifespan was reversed in duper hamsters as the mutation accelerated their adjustment to the shift of the light:dark cycles. Bittman says the findings have implications for pinpointing the pathways involved in human biological clocks.

“For people with jet lag or the millions of shift workers, it can take days and sometimes weeks for the body — the different organs — to come back into their normal temporal relationship,” he says. Many of us disrupt our circadian system when we are exposed to light late in the evening, such as by looking at cell phones and computer screens. “It can take a couple of weeks until your brain is having the right relationship to your liver and kidneys,” Bittman adds.

The research suggests that we all need to be mindful of how the environment affects our biological clocks. Specifically, hospitals need to be sensitive to the timing of lights and darkness in patients’ rooms. “We need to pay attention to the temporal relationship between organs and between the master clock and the brain, and how it regulates the clock in the brain, as well as in the peripheral organs, and be sensitive to the light:dark environment,” Bittman says.

Additionally, understanding the rhythms of the organs is a crucial aspect in the timing of medical treatment. “An awful lot of drugs that are administered are more effective at one time of the day than another because the circadian clock is regulating all these metabolic pathways that in fact are being targeted by these drugs,” Bittman says.

Ongoing research will focus on identifying the underlying mechanisms of the biological clocks and their role in disease.

But surprising new research published in Nature is adding a new, early chapter to the evolutionary story of gills.

“Our work suggests that the early, simplified gills of our worm-like ancestors played an important role in ion regulation. And that role might have originated as early as the very inception of gills, well before they played any role in breathing,” says Dr. Michael Sackville, a zoologist who led the study while with the University of British Columbia (UBC).

“This really does flip the script on our understanding of how gills and gill function evolved.”

The evolution of gills and lungs has fascinated biologists, including Darwin, for more than 100 years. Prior to this study, gills were thought to be first used for breathing and ion regulation near the very beginning of vertebrate life. In this traditional timeline, these two functions shifted from the skin to the gills in tandem, helping vertebrates transition from small, worm-like creatures to larger, active fishes. This transition from “small and wormy” to “big and fishy” is an iconic event in vertebrate evolution.

The study traced the evolutionary journey of gills by comparing three animals that are alive today, but belong to different lineages: lampreys, which are vertebrates, and amphioxus and acorn worms, which are close relatives of vertebrates. The researchers assumed that any gill functions shared between the animals were inherited from a common ancestor, which is believed to be when simple gills first appeared well over 500 million years ago.

“We found that gills were used for breathing in only our vertebrate representative, and only with increasing body size and activity,” says Dr. Colin Brauner, a UBC zoologist and senior author on the paper.

“But we found ion regulating cells in the gills of all three of our animals. This allowed us to trace the origin of ion regulation at gills all the way back to early deuterostome animals, when very simple gill structures are thought to have first evolved. The finding supports the classic story that gills were first used for breathing in early vertebrates, but adds an exciting new, earlier chapter to the story, clearly worthy of further study.”

The study was conducted in collaboration with researchers at the University of Montreal and Cambridge University, and funded by the Natural Sciences and Engineering Council of Canada and Royal Society.

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