Fly on the Wall

Making fly science approachable for everyone

Month: January 2015

Fly Life: Fruit flies in the science classroom

Do you remember sitting in the science classroom in grade school, looking at pictures of pea plants to learn about inheritance? What if you could have tested Gregor Mendel’s theories of inheritance yourself (without watching plants grow)?

Well, you can! As it turns out, fruit flies are a great teaching resource for the science classroom. They are cheap, easy to maintain and store, and are well-understood, since they’ve been studied by researchers for over a century. These characteristics allow teachers to set up hands-on experiments for their students, and quickly adapt to students’ curiosity-driven questions.

Fruit flies can be used for teaching a variety of scientific concepts, from genetics to behavior, and the related experiments can be engaging, fun, and easy to understand. I want to talk about some of my favorite examples (some of which have gone from science fair projects to published peer-reviewed articles!).

Inheritance and Evolution

Punnet square for red- and white-eyed fliesAn example of a punnet square for mating a white-eyed and red-eyed fly. The white eye is caused by a sex-linked recessive genetic mutation. Male offspring have white eyes because they only have one copy of the gene (the mutation) from the white-eyed “mother”, while female offspring have a backup normal “red” copy inherited from the “father”.

Do you remember doing the punnet squares for Mendel’s pea plants? Punnet squares are diagrams used to predict what traits offspring will inherit from two different parents, and is the most common way to teach inheritance in the classroom. Fruit flies, with their short lifespan and quick generation time (offspring are available in only two weeks!), are perfect for a hands-on version of this experiment. Flies with different traits (such as red eyes and white eyes, or curly wings and straight wings) can be mated. While waiting for the next generation, students can predict what percentage of the offspring will have each trait. Two weeks later, they can sort the flies to test their predictions.

UNC’s The Wonderful Fruit Fly website is great for seeing how punnet square experiments can be performed with fruit flies.

Red- vs white-eyed fliesThe fly on the top has a mutation that causes white eyes. The fly on the bottom has normal red eyes. source

Another great example for an experiment was described in an article published in the journal Evolution. Because multiple generations of fruit flies can be studied in a matter of months, students can actually see evolution “in action”. In the published example, students added a single red-eyed fly to a large population of white-eyed flies. Flies with white eyes have poor eyesight and are less healthy than flies with red eyes. Over the course of the experiment, students watched as the healthier red-eye gene spread through the population, simulating the way a random advantageous mutation in nature can spread via natural selection.

This is only a couple of the dozens of interesting genetic experiments that can be performed in class. For more examples, the Tree of Life web project site is a great resource. 

Behavior and Health

Dyed food experimentFlies that eat dyed food have colored abdomens. Image modified from Isono and Morita, 2010.

Although fruit flies are most commonly associated with genetics experiments, they can also be used for behavioral experiments. One of my favorite examples is testing flies for food preference, in which students can give a group of flies a choice between two or more food sources, and count the number of flies that land on each. To make it even more interesting, the food can be dyed different colors. Once ingested, the dye is visible through the flies’ abdomens, allowing students to count how many flies have chosen each food based on color. Wouldn’t it be cool to see blue and purple flies under a microscope?!

Food preference experiments from middle school science fairs have actually made the news a couple of times over the past two years. In 2013, student Ria Chhabra developed an experiment to test whether organic food really is better than conventional food. She raised flies on each type, and found that flies raised with organic foods lived longer and healthier lives. The results were published in the peer-reviewed scientific journal PLoS One.

A similar story was released in 2014, when student Simon Kaschock-Marenda wondered whether fruit flies would like artificial sweeteners as much as normal sugar. He raised flies on sugar and several different sweeteners, including Truvia. His results, also published in PLoS One, showed that erythritol, the main ingredient of Truvia, was actually toxic to fruit flies.

These two heartwarming stories demonstrate how fruit flies can be used in the classroom to inspire students to pursue curiosity-driven science.

Want to start using flies in your classroom? There are many resources available online for experiment ideas, as well as “How-to” guides for setting up and maintaining a fly lab. One of the most comprehensive is the “How-to Fly Manual” from the researchers at the University of Manchester’s Fly Facility.  Another great resource is the “Drosophila Melanogaster in the classroom” blog, which details how to set up a classroom using fruit flies.  

——

Many thanks to my friend Brittney for her help with resources and ideas for this post, gathered from her own volunteer experiences teaching fruit fly science to eager young minds.

I would also like to thank Dr. Andreas Prokop at the University of Manchester for some of the resources and inspiration for this post.  He and other fly researchers at the University of Manchester maintain an impressive array of lay information about fruit fly research and resources on their website (not just about how flies can be used in the classroom, but also how flies can be used to conduct high-quality research in disadvantaged regions and countries, where resources and funds may be limited).

 

Breaking Research: Fruit flies help uncover the brain’s link between sleep and memory

Researchers at Brandeis University have found that the link between sleep and memory is stronger than we thought. It is well known that sleep is important for learning and memory, and many people can attest to having a hard time focusing and remembering things after a bad night’s sleep. Students often receive advice about getting a good night’s sleep instead of late-night cramming before a test. Simply put, scientists have learned that the brain takes advantage of the quiet hours during sleep to transfer newly-learned memories into long-term storage.

But how exactly are these complex behaviors connected in the brain? Does sleep simply permit memory storage to take place, such that the part of the brain involved in memory just takes advantage of sleep whenever it can? Or are sleep and memory physically connected, and the same mechanism in the brain is involved in both? In a recent study published in eLife, researchers in the Griffith lab may have finally uncovered the answer. They found that a single pair of neurons, known as the DPM neurons, are actively involved in both sleep and memory storage in fruit flies.

Why the fly? Fruit flies may be less complex than humans, but they have similar behaviors such as sleep and memory, and their brains have a similar organization. You may have heard of the hippocampus: the seahorse-shaped brain region in mammals that is responsible for learning and memory. The hippocampus receives a lot of information from other parts of the brain, and it has been very difficult for researchers to sort it all out. Fortunately, fruit flies have a similar region called the mushroom bodies (MBs), which are also important for learning and memory. Even better, fruit fly researchers have identified many of the neurons that send information to the MBs. One such example is the DPM neurons, which are critical for long-term memory storage. If the DPM neurons (there’s just two of them!) are “turned off” so that they can’t communicate with the MBs, flies can’t form long-term memories. This gave the researchers a great place to start for studying how sleep and memory are linked in the brain.

To find out if the DPM neurons are also involved in sleep, the group manipulated the activity levels of the DPM neurons and observed whether the flies showed any changes in their sleep patterns (Click here if you want to learn more about exactly how we study sleep in flies). They found that the DPM neurons had a dramatic effect: hyper-activating them increased the amount of time the flies slept, while silencing them decreased sleep (remember that silencing them also shut down long-term memory storage). Thus, sleep doesn’t just permit memory storage. These behaviors are actually tied to the same mechanism—the same neurons!—in the fruit fly brain.

Dream WaterThe fact that DPM neurons use GABA and serotonin is another similarity to us. Those chemical promote sleep in humans too, and many sleep aids include GABA and/or serotonin supplements.

As the researchers delved further, they found that the DPM neurons were dampening part of the MBs’ activity using GABA and serotonin (both are chemical messengers that neurons use for communicating with each other). That part of the MBs was important for learning and, as it turns out, also signaling wakefulness. It’s almost as if that section of the MBs were saying “Hey, stay awake and learn this”. After a while, however, the DPM neurons may start signaling to suppress the MBs, as if to say “You’re going to need sleep if you want to remember this later”.

Finally, there was another interesting insight uncovered by this study. It is widely believed that long-term memory is stored when groups of neurons signal back and forth in an excitatory manner, progressively strengthening their connections with one another (you may have heard the adage “neurons that fire together, wire together”). Yet, the authors of this study found that the DPM neurons, which are critical for memory storage, are not actually excitatory. To the contrary, they inhibit a section of the MBs necessary for learning. What role does inhibition play in memory? This finding doesn’t answer that question, but it does demonstrate just how much work is left to be done.

 

 
Reference:

  • Haynes P.R., Christmann, B.L. & Leslie C. Griffith (2015). A single pair of neurons links sleep to memory consolidation in Drosophila melanogaster , eLife, 4 DOI: http://dx.doi.org/10.7554/elife.03868

New Year’s Special: Flies in Space (and other news from 2014)

Fruit fly researchers published thousands of papers in 2014, and several of them were picked up by the media. I even reviewed a couple of these popular stories on this blog. In April, the Seghal lab published a paper showing that sleep loss in young flies led to abnormal brain development and behavioral deficits in adulthood. In September, researchers in the Walker lab showed that increasing the levels of a molecule called AMPK in the guts of fruit flies could extend their lifespan, providing hope that we may one day be able to develop a pill to slow aging.

The most heartwarming story of 2014 came out in June, after a sixth-grader’s science fair project was published in the peer-reviewed journal PLoS One. Father and son worked together to discover that the artificial sweetener Truvia is toxic to fruit flies. Erythritol, the main ingredient of Truvia, is safe to consume for humans but quickly kills these winged pests. The researchers who worked on the project are now pursuing the possibility of using erythritol as a safe insecticide for fruit flies and other insects.

But perhaps the biggest news from 2014 involves flies… in space! Although many animals have been to space over the past several decades, fruit flies have recently proven to be ideal for studying the effects of zero gravity on earthly bodies. It’s widely known that microgravity (zero gravity) leads to rapid loss of bone density and muscle weakness, which is why astronauts spend a lot of time exercising while they’re in space. But did you know that microgravity also negatively affects the cardiovascular and immune systems? NASA recently announced a plan to send humans to Mars by 2030, but first, they need a better understanding of the long-term effects of microgravity on the body.

Fruit fly with fungusThis fruit fly is covered with a fungal infection after its immune system was compromised by 2 weeks in space. Image credit: Deborah Kimbrell/UC Davis

Space flies made the news in January 2014 after the results of a successful experiment were published in PLoS One by the Kimbrell lab. Researchers sent flies into space for 12 days to determine how zero gravity affects their immune system. It may seem like a short trip, but that’s about half the lifespan of your average fly (roughly the equivalent of sending a human into space for 40 years!). The researchers reported that flies subjected to microgravity had reduced ability to fight off a fungal infection compared to their earthbound brethren. Also interestingly, flies exposed to hypergravity (even stronger than Earth’s gravity) showed an increased ability to fight off the infection. The difference in immunity was caused by changes in the Toll pathway, an immune response which is also present in humans and other mammals. These promising results provided a leap forward in understanding how astronauts’ immune system may also be affected by microgravity.

Three more fruit fly experiments were launched into space in 2014. In April, a collaborative group led by Dr. Peter Lee sent flies into space for 30 days to study the effects of microgravity on the cardiovascular system (the experiment was named The HEART FLIES study). The second experiment was launched in September by a team at NASA’s Ames Research Center led by Dr. Sharmila Bhattacharya. The researchers hope to better understand how flies adapt to microgravity by studying changes in behavior.

The final experiment, launched in December 2014, was the maiden voyage of NASA’s newly-developed Fruit Fly Lab-01 project. NASA’s Fruit Fly Lab is a collaborative effort with a sophisticated set-up that researchers hope will improve our understanding of how spaceflight affects immune function. After 30 days in space, researchers will analyze the immune systems from three generations of flies exposed to various levels of gravity.

The results of these three missions should be published this year. Researchers at NASA are hoping that the findings will help them predict the physical challenges that astronauts will face during future space exploration, including the first human mission to Mars. NASA is also planning yearly sequels to their Fruit Fly Lab’s debut mission, so stay tuned!

References:

  • Baudier K.M., Nirali Patel, Katherine L. Diangelus, Sean O’Donnell & Daniel R. Marenda (2014). Erythritol, a Non-Nutritive Sugar Alcohol Sweetener and the Main Component of Truvia®, Is a Palatable Ingested Insecticide, PLoS ONE, 9 (6) e98949. DOI: http://dx.doi.org/10.1371/journal.pone.0098949
  • Taylor K., Michael D. George, Rachel Morgan, Tangi Smallwood, Ann S. Hammonds, Patrick M. Fuller, Perot Saelao, Jeff Alley, Charles A. Fuller & Deborah A. Kimbrell (2014). Toll Mediated Infection Response Is Altered by Gravity and Spaceflight in Drosophila, PLoS ONE, 9 (1) e86485. DOI: http://dx.doi.org/10.1371/journal.pone.0086485
  • NASA.gov

© 2019 Fly on the Wall

Theme by Anders NorenUp ↑

Protected by Akismet
Blog with WordPress

Welcome Guest | Login (Brandeis Members Only)