Dr. Sara Good is part of a research team who are investigating the genetic pathways involved in sex determination and differentiation of one of the world’s most fascinating creatures. Sometimes referred to as the ‘vampire fish,’ lamprey have captivated researchers because of their unusual biology and ancient lineage. Good’s research into these unique vertebrates is not only providing new insights into the evolutionary development of sex determination mechanisms across different species but has the potential to play a pivotal role in the future of the Great Lakes fisheries by assisting in the control of lamprey populations.

On this episode the research question is: “What can lampreys tell us about the complexity of sexual determination in nature?”

SARA GOOD: It’s probably nicer out here. At least so you can see it. So, we’re going to do some extraction. In fact, I have some of the lamprey samples, and we’re actually going to extract some DNA from eggs tomorrow.

KENT DAVIES: Today, we’re at the Laboratory of Evolutionary & Population Genomics at the University of Winnipeg.[i]

SARA GOOD: Yeah, I have eggs and milt from the lampreys and we’re extracting the DNA to sequence the genome.

KENT DAVIES: That’s Biology professor Dr. Sara Good, she uses a range of laboratory techniques in molecular genetics to study the evolution of genomes. Good is part of a team of researchers whose recent findings have potential to play a pivotal role in the future of the Great Lakes ecosystem. Her main focus is on the genetic basis of sex determination and differentiation in one of the most fascinating creatures in the animal kingdom.

Lamprey, a group of jawless fish with an ancient lineage have captivated researchers because of their unique biology. They’re also valuable models for studying the diversity and evolution of sex determination in different species.

On this episode the research question is: what can lampreys tell us about the complexity of sexual determination in nature?

From the University of Winnipeg Oral History Centre, you’re listening to Research Question- amplifying the impact of discovery of researchers of the University of Winnipeg.

 

KENT DAVIES: Dr. Sara Good will tell you that the environment can play a key role in shaping long-term evolutionary changes in populations of plants and animals. Likewise, Good’s environment growing up played a role in guiding her career towards becoming a population geneticist.

SARA GOOD: I am from Kingston, Ontario. I lived there until my undergraduate and my undergraduate at University of Toronto. My mom was librarian at Queen’s University. My dad’s a lawyer. My mom was a phenomenal reader. So, I think, definitely her love of books and indeed of all things literary influenced all of her children. And my dad had grown up on a farm, and he was very outdoorsy and loved to do stuff in nature, fishing, a little bit of hunting. So, I spent a lot of time with him for my love of biology. My mom was married before earlier to a mathematician, and I actually always loved math. And that’s in a way I sort of put math and biology together in what I do. I’m a population geneticist, which combines more sort of analytical thinking. So, I think they definitely did influence me.

KENT DAVIES: During her undergraduate degree at the University of Toronto, Good became interested in the field of population genetics.

SARA GOOD: And at that time, I wasn’t sure that I wanted to go into academia, but I was really interested in conservation. Something that still interests me. So, when I went to graduate school, I went to work specifically in a field called conservation genetics, which is a field dedicated to using genetic principles and genetic models to understand risk factors of populations. So, using genes, you can like estimate how big the effective size of a population is, you know, different concerns from a management point of view. Once populations get below a certain level, they really become risk of extinction as we know now. And so that was my original thought and I went on to do my masters, at Penn State. Yeah, I would say that for sure was my “a-ha” moment. That this was something that I was really interested in.

KENT DAVIES: For her masters, Good applied for a Smithsonian fellowship to work at the National Zoo in Washington D.C.

SARA GOOD: That was that was a fantastic experience. As a biologist, I worked at the National Zoo from 1994 to 1996. My masters was through Penn State, but the project was there. My project ended up being on a species called the giant kangaroo rat. And this is not that giant, but it’s big for a mouse. It lives in the what’s called the San Joaquin Valley, which is a huge, now agricultural basin. It was turned into agricultural land and the giant kangaroo rats, they’re solitary, and they make these huge mounds, and then they store all their nuts and seeds inside. But they were basically extirpated from the valley for agricultural purposes. So, I sampled the tail hairs and then I did a genetic analysis of those and found some really cool things, and had an amazing experience because I did the fieldwork with other people from U.S. Wildlife. Sleep in the day and go out in their trucks at eleven and put out our traps. And yeah, it was really fun. It was a great experience.

KENT DAVIES: For her PHD, Good’s research focus changed from animals to plants.

SARA GOOD: Conservation is a difficult field to work in because there’s so much bad news. And I’m kind of a ‘the cup is half full’ kind of person. I liked the idea of working with something that wasn’t living and breathing because of the dissections. My concern about the planet. So, I switched my doctorate into reproductive systems and plants. I’m still most famous for that work. I worked on many plant crops that we know, including apples and tomatoes. They have these interesting breeding systems where essentially, it’s beneficial for plants to be hermaphroditic. They need bees to move their pollen around for them. And as we know, there is also lots of concerns about this in the current world. Pollinators are declining worldwide. All plants that need pollinators to move their pollen from one plant to another will be affected. But self-incompatible plants they’ll be even more affected because they depend on pollinators. It’s beneficial for them to be hermaphroditic because they kind of don’t know if it’s going to be their lucky year to be a male or their lucky year to be a female. Like, are they going to get a big pollen load and be able to set a fruit, or is a bee going to carry their pollen away from them and they’ll father? They don’t really want to mate with themselves. So, of course it opens up possibility. You’ve got your own pollen and your own ovules. You could mate with yourself. I have a new paper coming out that estimates about forty-five percent of plant species have what are called genetically controlled, self-recognition systems. They have genes that recognize if the pollen is from the same plant and if it is, it doesn’t allow it to fertilize the plant. So, that’s another interesting topic that I’m dabbling in again recently.

KENT DAVIES: Good continued to work on plants until coming to the University of Winnipeg, when her research focus shifted once again, this time to studying fish.

SARA GOOD: So, my master’s in rodents, my Ph.D. was in plants, and I continued working in plants until I came to University of Winnipeg in 2008. And I had been collaborating on some questions with some other people working in fish, and fish are really cool because plants have a lot of different mating systems, but actually, so do fish. So, I’d always been sort of interested in fish for a variety of reasons. Within fish, I was looking at the way that genes change over time in different species and the different functions they can play. And from that point of view, lampreys are really cool. So, that I was interested in lampreys because, they are the oldest living vertebrate.

KENT DAVIES: Lampreys, ancient, jawless vertebrates, have earned the nickname ‘vampires of the deep’ because of their parasitic feeding habits. The lamprey lineage is long, providing biologists like Good with valuable insights into vertebrate evolution.[ii]

SARA GOOD: Vertebrates have been, on the planet for about 550 million years. And lampreys are the oldest extant. There were other really ancient lineages of vertebrates, but they all went extinct a long time ago. Lampreys represent this really ancient time. You’re going back to the very origin of vertebrates. And that’s why lampreys are so interesting, because there was abrupt and significant shifts that create the vertebrate body plan. Right? There is the development of the neural crest, development of the notochord and then the vertebrae, of many different, other physiological systems. The hypothalamus, pituitary gonadal axis. And lampreys are also the, the oldest living animal to have a thyroid. Lampreys also have a novel immune system. So, they’re also widely studied for that.

KENT DAVIES: Lampreys are also unique in the context of genome duplication, a process where an organism’s entire set of genetic material is copied driving evolutionary changes.

SARA GOOD: Vertebrates went through two whole genome duplications about 550 million years ago. So, right at the origin, right at the base of vertebrates. It gives an organism opportunity to take their existing genetic material and literally double everything and in vertebrates. It happened twice. So, they went from having, say, one set of chromosomes to having two to having four of all. You can imagine a pathway like where there’s all of these different enzymes required to like do something. But now when you duplicate your entire genome, you’ve duplicated all the genes that did that. So, you could take that same pathway and tweak it just a little bit. So, it took some of the genes and built upon those more complex networks essentially. Many of the individual genes would be lost. And then the chromosomes get rearranged so they end up being deployed like we are just having two sets, but the whole genome duplication sort of gives you an opportunity to refine and modify and make more complex already existing, molecular pathways.

And so, lamprey are interesting in this way because it was debated and debated and debated until just a couple of years ago whether lamprey had been through the same two whole genome duplications as other vertebrates. And it turns out that lamprey went through the first whole genome duplication, but then they diverged in their own lineage. They went through their first one but not their second one. The really cool thing is that they invented sort of some of the same things that later vertebrates did in, in their own way. Some of the genes and some of the pathways are shared, but other things like their immune system they ended up inventing a really effective immune system that’s completely independent of our own, but does, surprisingly, some very similar things. So, they’re very interesting organisms from this point of view is like, you know, the evolutionary toolbox, the way it plays around and comes up with things. Surprisingly, there’s been this ability to come up with similar things in their own, their own fashion. So, that’s the simplest way to put it.

KENT DAVIES: Equally fascinating is the life cycle of a lamprey. For the sea lamprey in fresh water habitats, it begins with a prolonged larval stage in which blind toothless larvae drift downstream and burrow into sandy or silty bottoms of rivers or streams.[iii]

SARA GOOD: As larvae, they are filter feeders. So, they are jawless animals. They basically open their mouth and they have like a little net at the back of their mouth that catches detritus and things. And they extract energy from this.

KENT DAVIES: Here, they filter-feed on microscopic organisms for several years before transforming into much larger parasitic juveniles.[iv]

SARA GOOD: During that metamorphosis period when they transform from these filter feeders into what will become a parasitic animal, their whole body goes through transformations. They don’t have true teeth, but they have, you know, it looks like it looks like teeth.

KENT DAVIES: The juveniles then migrate out to lakes, where they feed.[v]

SARA GOOD: As adults, they will grab on to a fish and they parasitized, the fish, they, they are estimated to drink. I think it’s two kilos of blood on average over that period. How frequently they switch between hosts isn’t completely clear. Sometimes, of course, they might kill their host. It’s also not known what else they get from the animal. Like we just talk about them as being vampires, it’s hard to study them because they’re on other fish. And then it takes, in the upper Great Lakes, it’s pretty much always around eighteen months. They swim back up. So now they’re much bigger. They’re anywhere from like 100 to 500 grams. That’s the size that they grow by parasitizing these other fish.

KENT DAVIES: After a year or so of feeding, they migrate back to the rivers and streams where they came from, becoming sexually mature along the way.[vi]

SARA GOOD: They swim back to these freshwater streams. They lay their eggs. Or there’s the milt, as it’s called, the sperm, on little burrows. There will be fertilization. And then they die.

KENT DAVIES: While sea lamprey are an important part of oceanic ecosystems, when introduced to the fresh waters of the Great Lakes, the shortage of predators led to an explosion in their numbers. The result was a major disruption of the Great Lakes aquatic ecosystem and mass devastation of commercial fisheries.[vii]

It’s believed sea lampreys first entered the Great Lakes system in the 1800s through manmade locks and shipping canals. Niagara Falls served as a natural barrier to keep sea lampreys out of the upper Great Lakes until the opening of the Welland Canal. Subsequent upgrades to the canal in the 1900s increased the spread lampreys even further throughout the system.[viii]

SARA GOOD: They got into Superior, Huron and Michigan in 1947. And then within seven or eight years, basically the salmon were extirpated from the Upper Great Lakes, and the trout, almost. And this cost like seven billion to the freshwater fishing industry. And of course, this is a huge catastrophe. And at that point, the Great Lake Fisheries Commission was established. And they’re the primary funders of my research.

KENT DAVIES: The Great Lakes Fisheries Commission is an organization dedicated to the management and conservation of fisheries in the Great Lakes region. One of their key focuses is population control of invasive species like lamprey. In previous years the sea lamprey control program, administered by the Great Lakes Fishery Commission, has successfully reduced sea lamprey numbers to ten percent.[ix]

SARA GOOD: It’s changed over time which rivers the lamprey come into but there’s about 5000 rivers in the upper Great Lakes basin. But lampreys currently today they are only spawning in about ten percent or four or five hundred. We don’t know why they select some rivers and not others. This would be an interesting thing to study, but they’re just in a subset.

In 1954 they established barriers. So, in the Upper Great Lake system, they’re spawning in these rivers, like four to five hundred rivers within the system. They will migrate downstream as juveniles or transformers as we call them into the lake, attach themselves to a trout or to whitefish. And then after that eighteen months, they go back upstream. So, they have barriers, for the adults so that they can’t migrate back up to spawn. And then they catch them and they still do this, and they still catch, like 100,000 a year. So, they’re controlled but not extirpated. And they also have cages to catch the juveniles. So, swimming downstream to go to the lake, they also catch juveniles. So, they have these barriers and traps to try to catch animals.

KENT DAVIES: Aside from barriers, the primary method used to control lamprey populations in the Great Lakes is the application of lampricides; chemicals that are toxic to lamprey larvae. This is applied to streams and rivers where lampreys spawn during the larval stage when lampreys are most vulnerable.[x] While this method is effective, it’s at administered at a significant cost.

SARA GOOD: So, it was costing them $390,000 to treat one river in one year. And that’s killing the larvae. And they do this. So, given that the life cycle is five years, like every four years or so, they try to spray each of the rivers that they’ve spawned in.  So, luckily, they don’t spawn in all of them. It’s an amazing group of people that I have had the opportunity to work at the Hammond Bay Biological Station. Like the amount of great interesting science, because it also has been a spin off for studying other fisheries. It’s a really great community. But yeah, they still wreak surprising devastation on the fisheries. And the goal is to keep them— The target is around ten percent of the historical abundance, but it’s still fluctuating quite a bit. And I think just last year it was a really bad year for the number of lamprey that are still making it to adulthood and getting into the into the lakes.

KENT DAVIES: Because the current model of regulating lamprey populations requires a significant investment of money and resources, the Great Lakes Fishery Commission has been funding research into alternative and more sustainable solutions.[xi] By deepening our understanding of lamprey genetics, Good hopes her research can lead to a more precise and effective strategy to control lamprey populations; mitigating their impacts on ecosystems.

SARA GOOD: The focus of my research over the last few years has been to try to understand the mechanism of sexual determination. The big insight that my group has had is that the way that sex is determined and even that sexual differentiation occurs in non-vertebrates is quite different than in vertebrates. We’re really changing our views about sex determination and differentiation as being more an integration of environmental and genetic aspects.

KENT DAVIES: Lampreys exhibit a unique reproductive process compared to many other vertebrates. They are characterized by a prolonged larval stage during which sexual differentiation and maturation are delayed until much later in their life cycle.[xii] When and how sex is determined in lamprey has been a deep-rooted mystery for researchers like Good.

SARA GOOD: They represent the first organism. The oldest vertebrate that is sharing mechanisms of sex determination and differentiation that are unique to vertebrates. So, what we’ve discovered is that of the gametes, the oocytes and the sperm, some of the genes that are involved in that determination, as well as some of the processes for the differentiation of the animal, which refers to the process of, you know, now you decided that you’re going to develop eggs or sperm. How do you develop the whole animal to, you know, release and have functional sperm and, you know, mature eggs, the mechanisms for that. So, I think most people know that mammals in sex determination occurs with the help, I’ll call it, of sex chromosomes. Right. So, males are usually XY and females are usually XX. These sex chromosomes, it means that the male— He’s producing sperm which are haploid. That would contain either X or Y. So, basically, you know, a dad determines whether the offspring, his mom is always contributing X. So, this keeps sex ratios around fifty percent. And then there’s a particular gene on the Y chromosome actually that really gets things going. So, if that gene is deleted or is on an XX, people always assume it’s the chromosomes themselves in some kind of way. But no, there’s a few genes on these chromosomes that are really important. So, were you to delete those, you know, you would get a different outcome. And then fish are like a whole other kettle of kettle of fish will say. [laughs] Yeah.

Some fish have sex chromosomes. And the genes that make you, male or female, are carried on those. Other fish don’t have sex chromosomes. They might, like, have a sex locus, like a gene that’s influenced it. But it’s not on chromosomes that are different in males and females. The point that I want you to get from this is that in non-mammals there’s some integration of environmental and genetic cues that determine whether you’ll be male and female. There’s no fish that are known that have purely environmental sex determination like reptiles. But many fish, there’s a little bit of environmental influence. And then that environment triggers genetic pathways that initiate the male or the female. This is important in lampreys because it wasn’t clear if it was genetic or environmental. So, people have done experiments to see whether it could be like in reptiles, where it’s mostly environmental. And there’s a little bit of evidence that density might influence the sex ratio.

KENT DAVIES: Another fascinating trait of a lamprey is program genome rearrangement which shapes their evolutionary trajectory and contributes to their adaptive capabilities.[xiii] This also may be a prominent factor in determining their sex.

SARA GOOD: Program genome rearrangement is found in some invertebrates. It’s found in lamprey. Basically, the sperm in the egg have twelve extra chromosomes. So, they meet, they fuse, and they start to make an embryo. All of those chromosomes are dividing through mitosis. Right? The embryo is getting bigger. But then on the third day, all of the descendant cells get rid of those twelve chromosomes and only the first little bit. So, that’s got to turn into the gonad, isn’t it? Because it’s not like this in humans. So, that you probably like I think— Many people know that the gonad is formed on like six to eight weeks, male or female is determined. Before you probably, you know, the brain knows where the brain is going to be. But around six to eight weeks, these genes on the X and Y turn on and say, “oh, time to make fallopian tubes or a vas deferens.” So, in lamprey, when the embryo first starts, it has all these extra chromosomes and then it gets rid of them. The early embryo actually is going to become the gonad because only those cells have the extra chromosomes. It’s not known what the function of these extra chromosomes are. But then you have to fast forward because they grow really slow. Because there are these filter feeders. It’s not until they’re closer to two years of age that you see anything happening. Before that, it just looks like— it’s called undifferentiated. It’s a little sack of cells but you can’t tell what’s going to happen with it. By about two years of age, if you do, histology. So, you do a cross-section, you can begin to see what look like potentially like oocytes, and we’re looking at the gonad I should say at that stage. And trying to coordinate it with gene expression to see what turns it on to make male or female. And because there was no sex chromosomes in what’s called the somatic genome, and there was no gene found, it was assumed it didn’t have sex chromosomes. But what we found is that in the animals that will become male, these extra twelve chromosomes get turned on. And the female— So, the animals that develop eggs, there’s very few genes that are expressed. Histologically, they don’t look like males but they start to express the genes on these hidden these twelve extra chromosomes. It’s actually like a hidden sex chromosome. Now this is me hypothesizing, but like, this is totally my own idea. It’s complicated for cells to have X and Y. Whenever you do things, you have to pair the X and the Y, but like the X is big in the Y is small, right. So, it’s kind of neat to have these chromosomes that are only in the germ cells. You know it’s not going to mess up any other organism. If you like, you know, have sex specific control. So, one of the things I’m trying to investigate is the males and females have the same extra chromosome because it’s not a hundred percent known yet. So that’s what my sex determination funding is on, is to determine whether females have exactly the same twelve chromosomes as males.

KENT DAVIES: While the exact mechanisms by which environmental cues influence sex determination in lamprey are not fully understood, researchers have discovered evidence that environmental conditions may be causing hormonal pathways or gene expression patterns to change.[xiv]

SARA GOOD: It’s just something controls whether these genes on these chromosomes are allowed to be expressed. And if they do, it says turn me down the pathway. So, it was thought it was either they play a role in those first three days or maybe something to do with the gonad development. I don’t think that completely because there are genes expressed on these chromosomes that are also expressed in females but it makes sense to control sex this way. Like it opens the opportunity for there to be some environmental influence on you making that decision. Then it would toggle cues to allow expression of these genes. So, the control of gene expression is really, really important. And so, there are lots of mechanisms in the body to control when genes are turned on. Like I always give this example which is just kind of stupid. But like of course, you know when you eat a burger or something, your body at that point decides to turn on all these digestive enzymes, right? So, it’s the same idea. Your body has all the genes, but it makes decisions about when to turn things on. So, I’m proposing that based on some environmental cues or cues I don’t know what those are yet, you make a decision to keep off or turn on these regions. So, you make the decision to become male or female.

KENT DAVIES: In scenarios where reducing overall population size is the goal, targeting genes or gene markers associated with sex determination can help shift the population towards one or the other.

SARA GOOD: The basic idea for genetic control is that you can either create a severe sex bias. So, you can have, you know, way more males and ideally you can make them sterile. So even if they spawn, the embryos die. If you can genetically engineer something like this, then you’re able to have yet another tool in your toolkit for a decreasing the numbers. And I think that’s more the way we’re thinking of it now. There are ways to sort of engineer these genetic control strategies so that they die out over a certain period of time. That would mean we might have to be continuously stalking the ones in the Great Lake fisheries. But given that you see how expensive the current control are, they are really considering that. One of the neat things about lamprey is that male and female sex differentiation are largely based on estradiol and testosterone. They have very low levels of testosterone and they don’t have an androgen receptor. So, all of these things also evolved, and we’ve discovered some really cool things about that recently. Males have a high or even higher levels of estradiol as females. We discovered three different estrogen receptors. They have three whereas humans just have two. And we’re seeing that they’re more highly expressed in some of the males. So, we think that’s it’s possible that there could be something to inhibit that. The development of the gonad and the animal through estrogen. That’s one idea.

Another idea is if we know the mechanism of sex determination, which I think that we’ll get some insights. In many fish, there’s like a packet of genes that interact together. There’s a molecular pathway and that leads to male or female pathway. And some of those genes are in this germline region. And in fact, one of the core genes in determined maleness is present in mouse is also present in the lamprey germline.

KENT DAVIES: The germline consists of cells that give rise to eggs or sperm and is passed down from one generation to the next during reproduction.[xv]

SARA GOOD: So that’s the one I keep banking on that if we wanted to manipulate something to make sterile males or even to stop development of males, we could target that one. And a lot of the genetic control options are about releasing sterile males or having higher numbers of males. But basically, you could create genetic lines that create mutations to create sterile males. Or we could have things that would disrupt the endocrine process for the development of the animal.

Another avenue that this could go is that there are native lamprey, some of which are also parasitic, like it’s called the silver lamprey, that lives in these freshwaters, but they don’t get as big. So, they don’t kill the animal. So, the reason why the sea lamprey are so dangerous is that they’re getting to be massive and they’re sucking the blood, you know, sucking this trout to death. If I could somehow accelerate the development and disrupt it so that they mature earlier and then they go to spawn smaller. Then they wouldn’t be a pest. So, manipulating the hormones, manipulating the genes or getting them to be sexually mature earlier. I think those would be my current ideas on strategies.

And there’s also been polls of like public opinion, you know, are people willing to consider genetic control options because, as you know, trans genetics are not always popular, but people are willing to consider it because they are such a phenomenal pest on the freshwater species. So, that’s some of the background, that we’re— this would be another tool, not necessarily something that we would aim for total extirpation. Because you don’t want to go too extreme and the effect on the environment. You wouldn’t want to have offshoots to other lamprey species. And it could be could be complicated that part.

KENT DAVIES: The scope and complexity of this research requires a dedicated team of students. Good is enthusiastic about mentoring this next generation of genetic scientists.

SARA GOOD: That’s like, for sure the most rewarding part of the work, because, the only real reason you’re doing this is to also create future generations of people that continue this on and continue to develop good scientists. I mean, you’re doing it to contribute to the literature, but it’s so phenomenal to train students that can do different things. Like many people will find students get some of the best direct mentorship from people one or two steps away from them in the academic hierarchy. It’s really nice to have people from all levels of that. By having— if you’re an undergrad having a masters student guide you. If you’re a masters, you know, having a PhD and postdocs can be general managers but also give a lot of help to the doctoral or master students. Like there is this, this network of advising that occurs within the lab. I think that is one of the ways that my lab is pretty good is by making sure that everybody feels included and comfortable asking other people in the lab group. I’m really dependent on having good students in analysis as well as other students— Like it’s easier to find students that can do the lab work. Having said that, you need it as much as accuracy is really dependent on having good hands in the lab. So, accuracy is like hugely important and repeatability. So, you really have to be on top of like all the projects to make sure that high quality data is coming out.

KENT DAVIES: Good believes her research team is close to understanding the key genes involved in sex determination of lampreys, an important step in developing new conservation approaches to ensure the long-term health and sustainability of fresh-water ecosystems in the future.[xvi]

So, back to our research question, what can lampreys tell us about the complexity of sexual determination in nature?

SARA GOOD: One of the things they’re showing us is that there were major changes in the genes that were recruited for certain functions in vertebrates. Obviously, it’s like evolution is continuous and, in the chordates there were already gene pathways there that were providing different functions. But it seems as though— This is very much my personal opinion here. There’s not, a simple hierarchy of one gene to the next, to another. We envision sex determination, differentiation now more as an interaction of environmental and genetic factors. And because of the sex chromosomes and the importance of this one gene in humans, we ascribe a lot to, you know, a binary and just a binary concept of sex. It is more plastic, right? For sex determination, I think we’re learning there is a core number of genes and lamprey seems to have those. So, whether you decide to become male or female. And then for sex differentiation, which is this whole process of developing a mature gonad. And then for, for mammals, there’s many, of course, secondary sexual characteristics. And those are determined largely by estradiol and testosterone that act as transcription factors that turn other genes on and off.

KENT DAVIES: Lampreys offer a window into evolutionary history and the variability of mechanisms that guide sexual determination in nature. By studying them, researchers can gain better understanding of the fundamental principles that underline sexual development and how these principles have changed over time.

SARA GOOD: So, we’re beginning to appreciate, from fish to mammals, the greater role this interaction of environmental and genetic signaling to create different traits.

KENT DAVIES: You’ve been listening to Research Question. Research Question is produced by the University of Winnipeg Research Office and the Oral History Centre.

The University of Winnipeg is located on Treaty 1 Territory, the heartland of the Metis people.

Written, narrated and produced by Kent Davies.

Our theme music is by Lee Rosevere.

For more on University of Winnipeg research, go to uwinnipeg.ca/research

For more information on the University of Winnipeg Oral History Centre, and the work that we do, go to oralhistorycentre.ca.

Thanks for listening.

 

 

 

[i] Laboratory of Evolutionary & Population Genomics, Accessed, June 9, 2024.

[ii] Sara V. Good. “A great leap forward in solving the long-standing mystery of sex determination in lampreys,” Ecology & Evolution May 13, 2022. Accessed June 24, 2024.

[iii] “Sea Lamprey Lifecycle,” Great Lakes Fishery Commission. Accessed, July 26, 2024.

[iv] “Sea Lamprey Lifecycle,” Great Lakes Fishery Commission. Accessed, July 26, 2024.

[v] “Sea Lamprey Lifecycle,” Great Lakes Fishery Commission. Accessed, July 26, 2024.

[vi] “Sea Lamprey Lifecycle,” Great Lakes Fishery Commission. Accessed, July 26, 2024.

[vii] Margaret F. Docker, J.B. Hume, B.J. Clemens. Introduction: a surfeit of lampreys in: Lampreys: Biology, Conservation and Control, Vol 1. (ed. Docker, M. F.) 1–34, (2015); Sara V. Good.“A great leap forward in solving the long-standing mystery of sex determination in lampreys,” Ecology & Evolution May 13, 2022. Accessed June 24, 2024; “Sea Lamprey: A Great Lakes Invader,” Great Lakes Fishery Commission. Accessed, July 26, 2024.

[viii] “Sea Lamprey: A Great Lakes Invader,” Great Lakes Fishery Commission. Accessed, July 26, 2024.

[ix] “Fact Sheet 5: Sea Lamprey Control in the Great Lakes,” Great Lakes Fishery Commission. Accessed, July 26, 2024.

[x] “Fact Sheet 5: Sea Lamprey Control in the Great Lakes,” Great Lakes Fishery Commission. Accessed, July 26, 2024.

[xi] “SupCon: Supplemental Sea Lamprey Control Initiative,” Great Lakes Fishery Commission. Accessed, July 26, 2024.

[xii] Margaret F. Docker. ed. Lampreys: Biology, conservation and control. Vol. 1. Dordrecht: Springer, 2015.

[xiii] Sara V. Good. “A great leap forward in solving the long-standing mystery of sex determination in lampreys,” Ecology & Evolution May 13, 2022; Smith, Jeramiah J., Carl Baker, Evan E. Eichler, and Chris T. Amemiya. “Genetic consequences of programmed genome rearrangement.” Current Biology 22, no. 16 (2012): 1524-1529.

[xiv] Margaret F. Docker, F. William, H. Beamish, Tamanna Yasmin, Mara B. Bryan, and Arfa Khan. “The lamprey gonad.” Lampreys: Biology, Conservation and Control: Volume 2 (2019): 1-186; Sara V. Good. “A great leap forward in solving the long-standing mystery of sex determination in lampreys,” Ecology & Evolution May 13, 2022; Tamanna Yasmin, Phil Grayson, Margaret F. Docker, and Sara V. Good. “Pervasive male-biased expression throughout the germline-specific regions of the sea lamprey genome supports key roles in sex differentiation and spermatogenesis.” Communications Biology 5, no. 1 (2022): 434.

[xv] Ayhan Kocer, Judith Reichmann, Diana Best, and Ian R. Adams. “Germ cell sex determination in mammals.” MHR: Basic science of reproductive medicine 15, no. 4 (2009): 205-213.

[xvi] Sara V. Good. “A great leap forward in solving the long-standing mystery of sex determination in lampreys,” Ecology & Evolution May 13, 2022; Tamanna Yasmin, Phil Grayson, Margaret F. Docker, and Sara V. Good. “Pervasive male-biased expression throughout the germline-specific regions of the sea lamprey genome supports key roles in sex differentiation and spermatogenesis.” Communications Biology 5, no. 1 (2022): 434.