In this blog post, Tara-Lyn Camilleri, a Ph.D. candidate at Monash University in Australia, discusses her newly published paper, “Maternal and paternal sugar consumption interact to modify offspring life history and physiology”.
About the paper
Varying the environment of an organism can alter their physiology, which in turn alters their development time, lifespan, the rate they reproduce, the survival rate of their offspring, their body size, and so on. These changes occur due to a plasticity of phenotypes, or the ability for certain observable characteristics within an organism to mould and change according to environmental changes — despite the genes remaining the same. In nature, environmental changes and stresses can take many forms, such as temperature or climatic, presence of parasites or disease, presence of predators, or changes in food availability and nutrition. We know these factors change phenotypes of individuals (remembering phenotypes are observable characteristics of an organism), but evidence is also mounting to suggest it can also change the phenotypes of their offspring.
We altered the diets of fruit fly parents to observe how diet alters the fitness of the parents, and, of their offspring as well. Evidence so far demonstrates that when the diet of the parent is altered, effects are passed from parent to offspring — beyond the transfer of genes alone. Following on from this, we wondered whether a diet that is optimal for parents would be optimal for their offspring. Traditional thinking tells us that there may be an advantage for offspring to have an environment that matches their parents. So far, evidence for this concept is mixed. It may be that a plant raised in the same type of light as its maternal plant does better, but how does this generalise to other organisms? If we expect that offspring that has a diet that matches their parents might live longer, will that be true for all diet combinations? Which parent passes on the strongest effects (especially since most studies do not consider both parents)? We sought to answer these questions by challenging both the parents and both sexes of offspring with a diet of either higher or lower sucrose; therefore enabling us to observe the effects of all possible combinations of diets represented in our study.
Instead of finding that offspring lived longer if they ate a diet that matched one or more of their parents — we found that if the diets matched between the parents (i.e. Mum and Dad both ate either high or low sucrose) the parents lived longer than if say Mum ate low sucrose and Dad ate high sucrose. Offspring from these ‘matched’ parental combinations; however, they did not live as long as offspring from combos where parents ate two different diets, respectively. This study revealed that a diet combination that is optimal for parents may not actually be optimal for their offspring.
About the research
One of the main reasons we used fruit flies in this study is because there is solid evidence to suggest that findings in a model species such as Drosophila melanogaster could be pertinent to other species. We share evolutionarily conserved nutritional pathways and related genes, making them a great model for studying the intergenerational effects of dietary changes. We believe that quantifying the effects that parental nutrition has on offspring fitness is important for a couple of reasons. First, this work lays the foundations for future studies that want to investigate how applicable these effects might be in humans. Second, the positive contribution this research has to the study of evolutionary processes and inter-generational phenotypic plasticity.
We were surprised by how complicated the interactions between parent diets, and between parent and offspring diets, were. This highlighted that these effects are not only important to traits like lifespan, but that parental effects are not simply additive. This means that the outcome for offspring can differ widely from one generation to the next, based on the interacting parental diets, in both magnitude and direction. Even the lifespan of the parents was affected by the diet of their mate—a very exciting and unexpected finding. The next challenge for us is to see whether these effects will hold up under different combinations of diets, and to investigate the effects of altering protein and carbohydrate content on offspring reproductive success—a very good proxy for fitness.
The challenges in setting up these kinds of experiments are that we need thousands of flies to conduct them—this means thousands of vials that need to be maintained every day. This type of high-throughput work requires many long days for months at a time in the lab! We are always thinking of new experiments and new ways to test these ideas but we are limited by what we can realistically achieve with the resources we have.
About the author
Although I always had an interest in nature and conservation, I became involved in ecology proper in a little bit of a round-about way. After a degree in Psychology, I worked in IT service delivery for a number of years, for both corporations and governmental departments. Although I enjoyed the environments and people I worked with, the work itself did not align with many of my interests. I therefore took an interest in ecology and science more generally as a hobby, and, during this time, I joined the Australian Orangutan Project. I spent many weekends sitting on stalls selling plush orangs to raise money for the organisation. My mother made palm oil-free soaps and we would travel all around Victoria doing markets to raise money and awareness. It was my interest in this that lead me to learn more and more in my own time, leading me to take the plunge and go back to university to study biology. I then worked part time for Zoos Victoria, and went to Borneo and Cambodia as part of my interest in and study of primates. Eventually, after some undergraduate studies, and a masters at The Australian National University, I ended up in my current position as a PhD student at Monash University, Australia.
I spend my spare time pursuing artistic hobbies, as well as spending time with my family and friends, and I like walking every day and hiking in nature as much as I can.
Enjoyed the blog? Read the research here.