Weevil Knievel: Daring to destroy endosymbionts that are no longer useful

I teach a fourth year undergraduate course where I introduce students to a wide range of bizarre and interesting endosymbiotic relationships. I have often wondered how transient these relationships are and have assumed that one partner or the other might continuously be trying to get the upper hand in the relationship. A recent research paper explores this question in greater detail in insects (h/t to Tristan Long for passing along the article).
Vigneron and co-workers explored the relationship between the weevil Sitophilus and its endosymbiont Sodalis pierantonius . They show that young adult weevils have very high numbers of the endosymbiont in their guts in order to generate the large amounts of tyrosine and phenylalanine required to make dihydroxyphenylalanine (DOPA) which is in turn required to make the cuticle essential for their exoskeleton. Once the cuticle is completed, these high DOPA levels lead to the active elimination of the endosymbionts in gut tissues. The endosymbionts are recycled using a combination of autophagy and programmed cell death. In contrast, the endosymbiont populations in reproductive tissues remain unharmed.
Using a combination of fluorescent in situ hybridization and scanning and transmission electron microscopy the authors clearly show that the weevils can effectively modulate the size and number of bacteriomes (structures that house the endosymbionts) throughout development. The images in the paper are amazing! The authors propose that such co-ordinated and targeted endosymbiont destruction avoids inflammation and the induction of the immune system and that this recycling may allow the weevil to recover some of the metabolites and energy invested in the earlier stages of the relationship. This is a really cool example of co-evolution! At first glance it seems that the weevil has the upper hand in this relationship, but it’s also important to remember that the endosymbiont has still managed to ensure its transmission to the next generation in germ-line tissues which is no small feat.

Citation: Vigneron et al., 2014. Insects Recycle Endosymbionts when the Benefit Is Over. Current Biology. 24: 2267-2273.

Guest post: Catching Invasive Beetles before they get boring

This is a guest post by a student in my graduate course.

Wood-boring beetles can be found cozied up in trees, lumber, furniture and other sources of wood worldwide, posing both ecological and economic concerns. These beetles lay their eggs beneath the bark of trees, where their larvae hatch and feast on the tree’s nutrients before developing into adults, tunneling their way out of the tree, and continuing on to infest new trees. These beetles have classically been restricted to the environments from which they originate, but the influx of international trading has allowed for “alien” species of wood-boring beetles to infest new lands. Although protocols are in place to stop the spread of wood-boring beetles, larvae of these bugs are able to remain undetected in wood that is used for packaging during international shipping, allowing them to hatch, reproduce, and spread upon arrival. These invasive beetles are especially problematic in their new environments because they frequently do not face the same ecological constraints that they would in their natural ecosystem, such as risk of predation or lack of suitable host trees to infest. While wood-boring beetles are rarely able to reach populations large enough to pose a risk in their native environments, they are often able to flourish in new ecosystems, spreading rapidly, destroying tree populations.
One example that you may be familiar with is the Emerald Ash Borer . It originates from Asia, where it is only a minor pest, as populations can rarely grow dense enough to kill healthy trees. However, after arriving in packaging material during the 1990s the emerald ash borer has thrived in North America, spreading rapidly while leaving a trail of decimated Ash trees in its wake. For over a decade, North Americans have struggled to limit the spread of the Emerald Ash Borer, with no easy solution in sight. It is apparent that wood-boring beetles must be further studied in order to track and limit their dispersion.
In order to improve the efficiency and cost effectiveness of measures to prevent the arrival and dispersion of invasive wood-boring beetles, the Italian researchers Davide Rassati, Massimo Faccoli, Edoardo Petrucco Toffolo, Andrea Battisti, and Lorenzo Marini investigated the factors that influence the arrival and establishment these beetles. As trading ports are considered the most likely point of entry for alien wood-boring beetles, the researchers selected fifteen Italian trading ports and surrounding forests to set up traps that were specially designed to attract and capture wood-boring beetles. Over 150 days the traps caught fourteen alien species, four of which had not been seen in Italy before. The more imports a port received, the more beetles that were found in the port and the surrounding forests. As these invasive beetles feed on broadleaf trees, they heavily preferred broadleaf forests, taking little time to infest their preferred host species. Upon arrival, the beetles quickly established themselves in the surrounding forests; more beetles were found in the forests than the ports they originated from. As it is desirable to stop the spread of beetles to the forests once they have entered a port, the researchers argued that that an early detection system is necessary to quickly catch and eradicate any invasive wood-boring beetles. They recommend that ports that receive high volumes of commodities, especially those surrounded by broadleaf forests, should be actively tapped and monitored for invasive beetles.
I agree with the researchers that the early detection of invasive wood-boring beetles is important to stopping them from spreading; however I believe that the emphasis should be placed on developing shipping practices that prevent the transport of invasive species, rather than hoping to detect and eliminate invasive species once they have arrived. By the time wood-boring beetles are detected, it is likely that they have already dispersed, requiring a long, costly cleanup, such as the Asian Long horned Beetle infestation Toronto suffered in the last decade. To prevent the spread of invasive wood-boring beetles, manufacturers must either use packaging materials that cannot be infested by the beetles, or more carefully treat their wood before shipping, both of which would come at increased international shipping costs. One must then ask: is it worth compromising the integrity of our ecosystems in the name of globalization?

Rassati D, Faccoli M, Petrucco Toffolo E, Battisti A, Marini L (2014) Improving the early detection of alien wood-boring beetles in ports and surrounding forests. Journal of Applied Ecology, online in advance of print.
Rassati D, Faccoli M, Petrucco Toffolo E, Battisti A, Marini L (2014) Data from: Improving the early detection of alien wood-boring beetles in ports and surrounding forests. Dryad Digital Repository.

Guest Post: Ski Bunnies Poop To Tell You How They Feel!

This is a guest post by a graduate student in my Ecological Physiology course.

Imagine for a moment, a place of blissful peace. What would it look like? A place with crisp fresh air, snow covered slopes and lush green forests. A place so quiet, that the only things interrupting the tranquillity are the odd howls of wolves, the rustle of small animals scurrying about and the cracking sound of tree branches under the weight of the snow cover. It is in just such a place, in the Swiss Alps, where our story of Lepus timidus, a happy little mountain hare, begins.
Lepus lived with his family in a cozy hole he had dug under the roots of an old pine tree. Many of his friends had done the same at nearby trees. Lepus (or Lepi as he liked to be called) and his friends were so close that they often gathered food, played and groomed together. Their grooming involved many hygienic procedures but none were as strange as eating their own feces. YES, I say, eating their own poop! Right about now you’re probably making faces and saying things like ‘Eeeew, gross or yuk’, and who would blame you? But did you know that this is a common and necessary behaviour for all animals involved in coprophagy (the act of eating poop)? Rabbits produce two types of droppings: fecal pellets from the colon and slime covered pellets that come from their caeca. By eating the latter type, bunnies are able to re-ingest nutrients they may have missed the first time around (still gross). In fact even pet bunnies will do this, followed by snuggling and bunny kisses (Mmmmmm, just food for thought). Ok, back to our bunny tale. Lepi, his friends and family were famous across the land for being so happy and relaxed all the time. Oh, sure they had the odd scare, when the neighbourhood fox fancied hasenpfeffer for dinner, but overall life was pretty serene.
One day all the peace and quiet came to an end when humans decided to move into the mountains to have some fun. They brought skis, snowshoes and snowmobiles and began to explore the forests where Lepi had lived for so long. They even erected buildings and tall metal poles strung with wires that allowed them to climb the mountain faster. They just hung there, off the wires, looking down at poor little Lepi and his friends, their enormous shapes casting dark shadows as they eerily moved along. All this human activity made Lepi and his friends very nervous. They began spending more time in their holes hiding and were afraid to go play and gather food. They were hungrier than ever which made their desire to groom very low priority. In fact they even stopped eating their own poop.
“This is not right”, yelled Lepi. “I am going crazy with all this commotion going on”.
Lepi took a deep breath, checked to see if the coast was clear and hurried over to see the family psychologist. The psychologist understood what Lepi was going through, in fact citing that he, himself, had been experiencing similar symptoms. He recommended that Lepi go see his scientist friends who could possibly determine what was happening to the once happy bunnies. So Lepi packed his bunny bags and hopped off to see Maik Rehnus, Martin Wehrle and Rupert Palme, prominent wild life researchers. Once there, the scientists assured Lepi that they would do everything in their power to determine the problem. Lepi was told that all he and his friends had to do is to try to go about their normal business and deposit poop pellets which they would collect and analyze. Excited, Lepi hurried back to share the news, although he wondered what the scientists were going to do with their poop. Lepi’s quick internet search revealed that there are hormones called corticosteroids which become elevated with increased stress. The metabolites of these corticosteroids are collected in the feces and excreted, therefore, an analysis of the poop could determine if the bunnies were stressed in certain situations.
The scientists began their testing in the Swiss Alps in three different locations where the hares lived. The first site was very busy with tourists and activity, the second site had medium activity and tourism while the third site was a natural reserve where no human activity and tourism was allowed. They worked feverishly over several winter months to collect all the bunny poop from the three different sites. Once back at the laboratory they determined that the poop of mountain hares that lived in the busiest tourism areas contained the highest levels of corticosteroid metabolites. The hares who lived in medium traffic areas had poop with medium amounts of metabolites, while the hares from the reserve had the lowest levels. This told the scientists that the presence of humans in the natural habitat of the mountain hares, caused unnecessary stress on the animals. This stress caused an elevation in corticosteroids concentrations in the hares. Corticosteroid release is a normal physiological response to the ‘fight or flight’ reaction, which enables the animal to make critical lifesaving decisions in face of perceived danger. Although some base level corticosteroids are always present in the blood, prolonged high levels may lead to various illnesses, presenting with symptoms such as lethargy, abnormal behaviour and loss of appetite.
In addition to this on site study in the mountains, the scientists invited a few select mountain hares to join them for a little while in their laboratory where they could perform some more psychological and physiological tests. The bunnies were divided into two groups and offered a nice enclosed place to do what they please, with plenty of food and a cozy shed to sleep in. One of the groups were left alone to live in peace with no disturbances, but as before their poop was regularly collected. The other group, however, was allowed visits from a curious dog who rummaged around the bunny compound. Also the scientists occasionally flew a kite above the bunny enclosure to simulate birds of prey. These bunnies also had to surrender their poop. Once again the scientists found that the hares that were being regularly disturbed had much higher levels of corticosteroid metabolites in their poop compared to the hares that were left alone. The scientists concluded that human activity and predation literally scared the crap out of these animals.
After the lengthy research the scientists called a meeting with Lepi and his friends to reveal their findings. The hares were understandably upset and concerned, but the scientists provided some compromises that would allow the mountain hare population to continue thriving without any further disturbance. It was recommended to limit human winter activity to the already developed ski slopes, not allowing backwoods skiing and exploration. This would allow the animals to get used to sharing the space without threat of disturbance. Other suggestions included a stop or reduction to further tourist development as well as limiting the number of tourists allowed per year per site.
Unfortunately not all stories have a happy ending. Although Lepi and his friends were glad to comply with these new compromises, humans were less enthused. These were important studies performed by the scientists, making recommendations to protect the animals; however, the owners of tourism based businesses are not under legislature, obligating them to follow these recommendations. The socioeconomic status of a small country such as Switzerland is highly dependent on the ever growing tourist industry and therefore it is unlikely that these compromises will ever be enforced. Last the scientists heard, Lepi and company were forced to uproot their families and move deeper into the woods further away from human activity. Hopefully development of these mountains will stop before the eradication of forests and ultimately countless animal species.

Citation: Rehnus M, Wehrle M, Palme R. 2014. Mountain hares Lepus timidus and tourism: stress events and reactions. J Appl Ecol 51: 6-12.

Introducing a Blogging Assignment into a Graduate Course

This term I am teaching a graduate course on Ecological Physiology. When I was designing the course I wanted to provide the students with an opportunity to write about science for a more general audience. At the same time, I had recently started blogging and using Twitter and was starting to see the usefulness of these forms of communication and felt strongly that these are practical skills that should be taught to graduate students within the curriculum. I therefore thought that I’d like to add an assignment to my course that required my students to write a blog post.

The assignment requires my students to select a recent scientific paper (less than 5 months since publication) that they find interesting and that they believe would make an interesting blog post. We’ve had several meetings to discuss their papers and their approach to writing and publicizing their blog post. Their performance will be evaluated on the content of their post (e.g. writing style, writing effectiveness, etc.) and the popularity of their post as measured by page views.

This Friday I will feature two guest blog posts by my students on the research papers that they have selected. As this is the first time using this assignment I expect that I and the students will learn a great deal and I look forward to sharing the results of this experiment!

Things that I Learned While Putting Together my Tenure Package

This fall I applied for tenure at my university. Below, I’d like to share some of the things that I learned putting the application package together. This includes a lot of legwork that I was glad I did over the past several years which made it much easier to organize and articulate my arguments for why I should keep my job.

1. It is never too early to start thinking about your tenure package. I advise all new faculty to start a paper filing system for each year that they are on the tenure-track as well as an electronic filing system for digital materials. When you do something that is relevant to research, teaching, service, outreach, etc. put something that documents that activity into one of these folders. Your future self will be emphatically thanking your past self when tenure time rolls around. This is also a handy tip for completing annual activity/performance reviews.

2. Use your calendar to document meetings and events and make sure that your calendar records from previous years are accessible and searchable. It doesn’t matter if you prefer to use a paper or electronic calendar, but having a tangible record of past efforts is extremely valuable.

3. As soon as you start your job make a list of what materials might be relevant to include in a tenure package; some of these are not obvious. This step allows you to plan ahead. When you start your tenure track position, think about what information is useful to include in your tenure package. For example, I conducted my own teaching evaluations in addition to the official institutional ones. This allowed me to get some useful comments and feedback from my students about my teaching. I used these evaluations as another line of evidence to support my claim that I am an effective and engaging teacher. Are there any graduating students that you would like to approach for letters of support before they move on? When someone sends you an email to thank-you for something that you did, make sure that you save it. Try to keep duplicates of important documents. Papers get lost and computers can cease to function at any time.

4. Keep that CV updated every month. I have a standing appointment in my calendar that reminds me to update my document once a month. It is amazing how many different things you can accomplish in just 30 days! If you stay on top of keeping track of what you’ve done as you go, you won’t be rooting through piles of paper or electronic files years later. Keeping your CV updated is also a good idea so that you can take advantage of opportunities that have tight deadlines (e.g. collaborative grants, award nominations, guest speaker invitations, etc.) when a current version of your CV is requested.

5. Preparing your tenure package is a great opportunity for self-reflection and to feel proud of what you’ve been able to accomplish in a few short years. It gives you some time to think about where you’ve been, where you currently are, and where you want to go next. The other side of this is that it is also an opportunity for the imposter syndrome to rear its ugly head and cause a great deal of self-doubt. Be kind to yourself during this process. Accept that you have done your best given your individual circumstances. I was up for tenure at the same time as a colleague and we offered each other support, advice, and encouragement during the process which was immensely valuable.

6. Don’t leave it to the last minute. There is a lot of personal and professional reflection that needs to occur during this process. I started working on my package at the beginning of the summer and did little bits and pieces here and there. I completed the content of the package by the end of July and then went on an extended vacation. When I came back I made some final adjustments, but by that time all that was left to do was organize and assemble the package.

7. This is one time in your life where you do not want to be modest. You need to toot your own horn effectively, but do it in a way that is not off-putting. Make a statement, support it with evidence, and build your case. Don’t make people put two and two together or read between the lines.

8. Ask several colleagues to look over your package before you submit it. They will see things that you don’t and will make excellent suggestions for improvement. Be sure to ask people who will not be in a conflict of interest (e.g. avoid co-workers on the tenure committee or who will be voting on your package).

Any other tips to offer on putting together a tenure package? Feel free to leave advice in the comments!

Active Learning Exercises for Teaching: Photosynthesis

I teach a 3rd year Plant Physiology course and a 4th year Environmental Stress Biology of Plants course. In both of these courses I go into quite a bit of detail about photosynthesis. This is material that my students have been exposed to in previous undergraduate courses, but in the context of these two courses my aim is to show students why the process of photosynthesis can be a double edged sword. I think that most people assume that plants love any level of light and that the more light that plants have access to the better. We often talk about photosynthesis as a steady-state pathway when in reality plants are constantly acclimating to their light environment likely on the timescale of milliseconds. I use an active learning exercise in my classroom in order to teach my students that photosynthesis is a dynamic process fraught with dangers for plants.
For this exercise I bring in a bag of soft plastic balls. These were left over from a ball play-set that my son had when he was younger (think the ball pits that you can find at IKEA or that used to be present at indoor play areas). I also bring in a large metal bucket. I ask for 6 volunteers from the audience to participate in the activity. Each student represents a complex/mobile carrier involved in the photosynthetic electron transport chain (e.g. photosystem II, plastoquinol, etc.) and the last student in the row is the enzyme ferredoxin-NADP+-reductase. The balls are used to represent electrons. The first student’s job is to accept the balls that I pass to them and then pass them to the next student. The other students in the chain in turn accept the balls and pass them along the chain. The last student in the chain aims to deposit the balls in the metal bucket. The bucket represents the ability of the plant to use the electrons to produce NADPH and ATP and to fix carbon.
The first time through the exercise I put balls into the chain at a very low rate. This shows the students that sometimes plants can have difficulty generating energy and fixing carbon if light is limiting. This would be similar to severe shading effects for example. I then put the balls into the chain at a reasonable rate. This represents a “steady-state” for photosynthesis where the process is running efficiently. For the last part of the activity I put the balls into the chain at an extremely high rate; as quickly as I can pass the balls to the first student in the chain. Inevitably the balls get dropped frequently at various parts of the chain and many of the balls do not make it into the bucket, or the bucket overflows. I use this to demonstrate over-reduction of the electron transport chain and to explain the generation of reactive oxygen species during photosynthesis.
Based on previous course evaluations, the students enjoy this exercise and claim that it helps them to remember key aspects of the photosynthetic electron transport chain. I’ve found it to be an engaging and effect way to teach about photosynthesis in my classroom.

See You in September

I’ve always liked September because it signifies new beginnings. I think this way because I’ve been in school in some form or another since I was 5 years old; first as a student for many years and now as a professor. September means super deals on school supplies in store flyers, like the fancy pens that I like and my favourite notebooks. I must admit surprise upon seeing that paper hole re-enforcements are still being sold. Whenever I think of September, I always think of freshly sharpened Laurentien pencil crayons (Peacock Blue or Cherry Red anyone?) I could spend hours happily walking the aisles at our local Staples store…
At my university September is also when the campus comes alive again. Although many of us have been on campus all summer, September is when the vast majority of our undergraduate students return to school. There is a feeling of nervous energy and anticipation that exists in the air during the first week of September that is comfortingly familiar.
My children also returned to school this week and the list of required supplies hasn’t changed much since my times in elementary school with the exception of one item. Evidently it’s no longer called Liquid Paper; it’s now correction tape.
Best wishes for a great first week of the semester!

Self-Promotion as a Female Scientist

Over at the Dynamic Ecology blog there’s an interesting poll and commentary on the topic of self-promotion in science. Many of us in science are introverts. Self-promotion is therefore unnatural and uncomfortable. In conversations that I’ve had with scientists over the years it seems that biologists are quite divided on whether self-promotion is a good or bad thing. Regardless of how you feel about it from a personal or ethical standpoint, I would make the argument that self-promotion in science is necessary in today’s funding climate. Some trainees and early researchers that I’ve talked to recently still seem to harbour the mistaken belief that if you publish well and do good science, your science will speak for itself, and the meritocracy of science will see fit to reward you. I think that this is a dangerous fallacy that has hurt many a career. Similar to networking, it seems that many scientists see self-promotion as dirty or unseemly behaviour. As universities continue to realize the importance of community engagement and knowledge mobilization in recruitment and advancement the pressure on scientists to self-promote will only increase. Whether you agree with this or not, in order to survive and thrive, you’ll need to learn how to promote yourself, your trainees, and your work.

 

I can reveal the importance of self-promotion in science by sharing a personal anecdote. When I was a Ph.D. student I made a discovery that was a big deal in my field of research; I discovered a new bio-energetic pathway in animals. I wanted to share my results with animal biologists and I felt that the best way to do this was to present my results as a talk at the annual meeting of the Canadian Society of Zoologists (CSZ). I put together the best talk that I could, wrote an effective abstract, and went to register for the conference. Going to this conference was a big deal for me because most of the work that I had been doing was in plant biology; I had only recently started working in an animal system. I therefore had a gigantic case of imposter syndrome. Each year the CSZ holds a competition for the best student presentation delivered at the annual meeting, but in order to compete you need to self-nominate by ticking a box during registration. I did not tick the box. After all, who was I but a plant biologist invading the domain of animal biologists? Long story short- I gave an amazing talk that likely would have won me the award, but I had taken myself out of the running. It was an epic fail in self-promotion. The next year I put my hat in the ring and won the honourable mention for the award. It was an important lesson to learn early in my career.

 

I am also conscious of the fact that some of my hang-ups about self-promotion are due to the fact that I’m a woman. I’ve been socialized to keep my head down, do my best, and hope that I’ll be duly rewarded. It’s taken a lot of work to get to the point of realizing that I need to toot my own horn and be proactive about telling others about my research. I can’t afford not to.

 

Aphids, ants, ladybugs, and wasps! Oh my!

We have a strange phenomenon occurring in our backyard. It started a few weeks ago when I noticed a pair of wasps engaged in a death match on our deck in the back yard. This event happened with regularity over the next few mornings, but I didn’t think much of it at the time.

Later that week we ate outside on the deck and were impressed by the huge numbers of wasps visiting our maple tree. I should say that my husband and I were impressed; our kids were very uncomfortable.

Fast forward to last weekend when I went outside to do some internet surfing on my tablet. The first thing that I noticed was the huge number of black ants running around our deck and all over the patio chairs and table. Being a biologist I also noticed that the table was covered with aphids and that the tree was infested with them. As I sat there for several minutes, it felt like a very mild rain shower was taking place. I realized that the aphids were excreting excess sugar in the form of honeydew and that there were so many of them that the screen of my tablet was covered in aphid poo in a matter of a few minutes! I’m guessing that the ants were going wild for the honeydew and that explains why they were running frantically all over the deck and furniture. Once I figured this part of the mystery out, I was also able to see a large number of ladybugs and their eggs in the maple tree. Ladybugs love to eat aphids and were taking advantage of this buffet opportunity.

But what’s the deal with the wasps? I’m not an entomologist, but there appear to be two species visiting the tree: the common yellow jacket wasp and something that might be a bald-faced hornet. Be doing some quick reading I discovered that the adults of both of these species eat nectar, tree sap, and fruit pulp. Perhaps the aphids have made tree sap readily available by feeding on the maple tree, or perhaps the wasps are eating the honeydew waste of the aphids deposited on the leaves. The other possibility is that the wasps are preying on the aphids and chewing them up to feed to larvae back at the nest. The wasps don’t appear to be a parasitoid species preying on the aphids.

It’s very cool as a biologist to see a food web occurring in your own backyard. This phenomenon has also served to remind me of the importance of observations in solving biological mysteries and testing hypotheses.

 

Flipboard: Finding current science news stories for use in your classroom

In the courses that I teach I’m always on the look-out for current news stories that are directly related to course content. One source that I’ve found to be a great source for these particular stories is the app Flipboard. They have a science section which is a great source for stories being covered by the popular media. Below are a collection of stories aggregated by the app within the past 24 hours.

If you teach a virology course, spending some time talking about the recent discovery of vials containing smallpox in Maryland  would be directly applicable to the course content and will likely grab the attention of your students.

Talking about plant dispersal in your botany course? EarthSky has written a great summary of an article about how migrating Arctic shorebirds are spreading mosses and liverworts  to new areas of North and South America. The plants may hitch a ride in the feathers of the birds.

Really into amphibians and conservation biology? Check out this Associated Press article on the hellbender; a giant salamander that is rapidly declining in population in the United States.

If invertebrates are more your thing, you’ll be amazed to watch the video of a purple siphonophore in this article from the Huffington Post.

I do a section in my Endosymbiosis class where I talk about all kinds of amazing and gross parasites. Talking about how a targeted eradication effort has almost wiped out the guinea worm in Africa  would be a neat way to talk about how public health efforts are changing our ecosystems and the natural world around us.

I’ve just given biological examples above, but the app collects stories related to many areas of science and engineering that could be used to bring your course content to life.

Feel free to share other news story resources that you use for course material or for general interest in the comments below.

 

 

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