Author Archives: Misaki Foster

Where is cell division located in the wing imaginal discs of caterpillars?

Misaki Foster

Mentor: H. Frederik Nijhout, Ph.D.

Biology Department, Duke University, Durham, North Carolina

Developmental biologists are looking to answer the question of how tissues grow to their species-specific size, and one way to begin to answer that question is by analyzing how patterns of cell division change over place and time. In this study I analyzed the patterns of mitosis and DNA synthesis in developing insect wings, the wing imaginal disks. The wing imaginal discs of caterpillars during their final larval instar are dissected and removed before staining with Hoechst and EdU so as to be able view and analyze mitosis and DNA synthesis, respectively, using a fluorescence microscope. Nuclei undergoing cell division are manually digitized and run through MATLAB programs to create a contour map that conveys where mitosis occurs the most. Overlay images are created to capture and highlight areas where DNA is being synthesized by the cells within the imaginal disc. Each method is repeated throughout different growth stages to determine how the patterns of cell division change as the wings grow and change shape. It is hypothesized that, in any given stage, mitosis will mostly occur in the areas where DNA synthesis does not occur, and vice versa. The results of this study show that cell division is not homogeneously spread across the growing wing, but occurs in ever-changing discrete regions.

Carnivorous Plants in Research

On the final day for ChalkTalks, most of the presenters- including myself- focused on ecology in our research. Personally, out of all of the amazing presentations that occurred over the three days, the one that stuck out to me the most was Ali’s talk about her pitcher plants.

She drew three different species of the carnivorous plants on the white board, one was small and wide without a lid to cover the top opening, another was taller and narrower with a lid to cover the opening, and a mix between the two with a medium size and a lid that partially covered the top opening of the pitcher plant. What her lab noticed was that there is a larger and more diverse bacterial population in the short pitcher plant without the lid, and the rainwater that is collected allows the diverse bacteria to thrive. The bacteria living within the plant also breaks down any insect that falls in the pitcher, thus maintaining a commensalistic relationship. In the taller species with the lid, less rainwater enters the pitcher, so less bacteria can thrive in the environment. However, because of this, more of the energy from the insects that become victim to the tall pitcher plant can be obtained instead of it having to share with the bacteria colonies. It is thought that the hybrid species that shares traits with the tall and the short plants houses an environment somewhere in between.

I am eager to hear more about Ali’s findings with her project and to learn more about these intriguing carnivorous plants.

How I’m Probably Slowly Ruining My Vision

At the Nijhout lab, I work with imaginal discs, which are about half a millimeter in size on average. From the time that I get there around 10-11am to the time that I leave the lab around 6pm, I’m either looking under the microscope or staring at a computer.

My typical lab days have become steady enough that I’ve figured out how to stick to a comfortable schedule. Because my imaginal disc batches have to sit overnight, the first thing I do in the late morning is rinse them out and continue adding and washing out different chemicals while working under the microscope. After the procedure is complete and some time has passed, I set the batch onto microscope slides and add coverslips. I then move to a different room that houses a larger microscope with higher magnifications so I can analyze either mitosis or DNA synthesis in the stained discs on the computer. If I feel that I have enough time before 2pm rolls around, I’ll select more caterpillars for dissections, stain them, and let them incubate for 2 hours while I go off to lunch and/or discuss with my PI what my next steps for the project should be. When I come back, I “fix” the discs with formaldehyde (still working under the microscope) and put them in the refrigerator overnight so that I can repeat the process the next day.

It might seem monotonous or boring to some people, but it makes my day to see the stained imaginal discs under the high powered microscope and learn more about my research. I am glad to come into work everyday to continue learning something new.

Caterpillars, Puzzles, and How Research is Similar to Marriage- with Dr. Nijhout!

On Thursday, May 27th, I had the pleasure of sitting down with Dr. H Frederik Nijhout to ask some questions about his career and research. During the interview, we talked a little bit about his academic background, goals in research, and fun anecdotes. I am aware that this is a very long entry, but please stick around until the end for what I believe is really important advice for anyone looking into doing research as a career!

** I will be paraphrasing his answers due to the fact that I am a slow typer and was not able to record his answers verbatim.

Q: To start off, what schools did you attend for your bachelors, masters, and PhD degrees? 

Dr. Nijhout went to the University of Notre Dame for his undergraduate studies. He then went to Harvard for both his Masters and PhD degrees. Thereafter, he pursued 2 postdocs via the University of Washington and the National Institute of Health.

Q: What did you major in? 

“Biology all the way.”

Q: What was your thesis project for your PhD? (simplified) 

His project tackled questions regarding the control of metamorphosis in insects such as “How are the hormones for this process controlled?” and “How does an animal know when it is time to secrete the hormones to metamorphose?”

Q: What were your goals when you first started research? How does it compare to your goals now? 

In part, Dr. Nijhout is still working on the general question he worked on during his PhD, fine tuning it with other questions that come up along the way. He found that time isn’t a factor into when an insect secretes the necessary hormones for metamorphosis. The defining factor is what researchers call the “critical size” or the certain size the insect needs to reach before entering the changing process. The questions his lab is pursuing now are along the lines of: How do animals grow to their species-specific size? How do they know how large they need to grow and when to stop?

Q: What classes do you teach? 

Entomology (general insect biology course), contains labs and field trips to collect insects and take photos. Capstone seminar for seniors: Physiological Genetics of Disease (unrelated to insects), tracks down the pathway of specific diseases and their mutations.

Q: How has your teaching experience been like so far? 

Dr. Nijhout enjoys teaching and has never seen it as a burden. He really likes being able to convey his knowledge to his students and has found that he always learns something new through this profession.

Q: What is your favorite part of your career? 

He enjoys solving puzzles and working out the mechanisms of what was unknown or not as understood before.

Q: What is your least favorite part of your career? 

We both laughed at this question because he has already told me how he does not like writing applications for grants and trying to find funding for his projects.

Q: Why did you choose to concentrate your research on butterflies and moths instead of any other insect (i.e. beetles, rollie pollies, dragonflies)? 

The main reason is because of his PhD lab, but caterpillars are also easy to rear, are inexpensive, and are large enough for such things as dissections.

Q: What is your favorite thing/ fact about caterpillars? 

Dr. Nijhout needed a second to think about this question, which I found quite funny because of how often he handles them. He ended up telling me that in general, people think the butterfly is the insect researchers know more of, but they spend much more time handling the caterpillars. It’s not the butterfly but rather the caterpillar that has to measure its own size and know when to metamorphose.

Q: Most embarrassing moment in a lab? 

He couldn’t think of anything particularly embarrassing, so he instead told me about an instance where he dropped a large bottle of alcohol on the floor. The lab began to get a little drunk off the vapors- not very fun at all. That plus the high flammability made the situation really dangerous, so they had to call in the emergency cleanup crew.

Q: Favorite memory in a lab? 

One of his grad students figured out how caterpillars know their own size- a question he had been working on for 20-30 years. He was very proud of her that day.

Q: Have you ever been scared in the field? 

No, but one time he was in Kenya collecting animals in an elephant preserve off the coast just south of Mombasa. His group spotted a mother elephant and her calf crossing the field, so they were told to get back in the car to leave the area. When they started to drive, the mother circled around and bellowed to scare them away. It was a thrilling experience!

Q: What is a piece of advice you would give to anyone looking into research as a career? 

Dr. Nijhout and I have had this conversation prior to the interview, and I believe it is a very important thing for anyone to keep in mind. Go into research because it’s the best thing you can imagine yourself doing. Do it because it is inevitable, because you really want it. The decision to pursue research as a career is similar to the decision to get married: you do it because it feels good and right. It is completely emotional.

This was probably my favorite Q&A out of the entire interview. I believe there is a lot to learn from working in a lab and toward your dream job. I am very excited to continue working with Dr. Nijhout and becoming more knowledgable about this field!

The Growth of Wings and Experiences

Butterflies are something that society has deemed beautiful, and we see countless different species all around the world, all with their own shapes, sizes, and colors. However, not everyone stops to think about how butterflies have come to have such diversity. Many researchers have taken on the task of looking into this question. I am very lucky to be working alongside some of these people.

This summer I am working in Dr. Nijhout’s lab, of which is researching growth in different insect species, meticulously dissecting a lot of caterpillars, albeit with many errors as of now. My objective is to remove the wing that is developing inside of the specimen, to dye it, and to prepare it on a microscope slide so that we can observe the pattern of mitosis occurring throughout the wing disc. It is interesting to see the wing discs at different developmental stages coming from a batch that is the same age. I can remove a disc from one caterpillar that has a beautiful set of veins that have grown in a couple of days. Then I can dissect a different caterpillar from the same container and see that the veins haven’t grown much at all within the same period of time.

When we look at these discs under the microscope, a large mass of nuclei come into focus (with the help of the Hoechst dye). Our job is to take note of the abundance and location of the cells currently going through mitosis. Being that I’m a beginner, it is still quite difficult for me to differentiate between two lumps of nuclei and anaphase, but I am determined to improve with all of Dr. Nijhout’s tips and advice.


One Step Closer to My Dreams Thanks to Caterpillars

There has been a lot of change for me lately: moving from west campus to east campus, being away from home (and thus away from my amazing cat, Oreo) for the summer AND fall semester, working through a long-distance relationship for these next couple months, and finally getting experience in a research lab for the first time. Sometimes I become sad thinking about all of that distance, but then I remind myself of all of the new people I am meeting this summer and all of my friends that I can continue to see and hang out with when I’m down. I remind myself that, every time I step into my new lab, I am one step closer to actually obtaining my dream job, and I know that I am very lucky to be able to make such a statement of comfort.

I have always loved animals, but being a veterinarian was not in the cards for me. Over the years, my desire to combine my love for animals and learning has multiplied, so entering the research industry seemed to make the most sense to me. This summer I will be working in the Nijhout Lab, where we’re studying growth of wings developing inside caterpillars. I have not met everyone yet, but the people I have met so far are very kind and welcoming. I was afraid of my first caterpillar dissections, but with Dr. Nijhout’s help, I was finally able to remove the imaginal discs from each side of the insect (unfortunately, I tore some of them). I can’t wait to learn more lab techniques and to assist this lab team with their goals. My main goal for this summer is to make new connections and get lots of hands-on experience in the lab!