12.20.24

Does the heat turn caterpillars into cannibals?

Kale in the lab setting up an experiment with fall armyworms.

The activities are as follows:

Around the world, temperatures are rising from climate change. This is a hot topic for scientists because warmer temperatures could make diseases spread a lot faster. Many diseases spread by the foods we eat. With warmer temperatures, metabolisms increase, and organisms need to eat more food to survive. This increases the risk of eating something that will get them sick.

When Kale started graduate school, they joined a lab that studies how climate change affects the spread of disease in fall armyworms, a type of caterpillar. Fall armyworms are an agricultural pest known for destroying corn, soybeans, and other crops worldwide. In the summer, they move into fields and rapidly chow down on crops. It’s often reported by farmers that it seems as though fall armyworms can remove all the leaves from a cornfield overnight! Believe it or not, their huge appetite leads them to another food source – they will even turn into cannibals and eat each other!

Once Kale started graduate school, they became interested in how cannibalism can increase disease spread in warmer temperatures. Fall armyworms can get infected with a special type of virus called a baculovirus. Baculoviruses are a group of viruses that infect insects, especially caterpillars. They are highly specialized, meaning that each baculovirus usually only infects one species.

A fall armyworm that has been liquified due to a baculovirus infection.

If a fall armyworm eats a fellow fall armyworm that is infected, it can be deadly. In fact, the disease causes their body to completely liquify into a puddle of pure virus! This baculovirus is so effective that farmers even use it to help control infestations in their fields. Since this specific baculovirus only infects fall armyworms, it is safe to use on crops without worrying about effects on humans or other living things.

To study how cannibalism can affect disease spread, Kale designed a set of experiments. They thought that when temperatures are higher, the larvae’s metabolism would increase and make them hungrier caterpillars. Increased appetite could then lead to more cannibalism. As a result, more larvae would be eating others that are infected, further spreading the deadly baculovirus.

To test these ideas, Kale set up small Petri dishes and placed one big fall armyworm in each dish as the focus of each trial. Kale added a piece of insect food and a smaller fall armyworm to each dish. This way, the larger caterpillars had the option of eating the insect food, cannibalizing its smaller friend, or munching on both.

To see if temperature had an impact, Kale set up three treatments at low, medium (ideal), and high temperatures. They assigned 40 Petri dishes to each temperature. To test changes in disease transmission, half of the smaller caterpillars were infected with baculovirus, and half remained uninfected.

Kale predicted that fall armyworms at higher temperatures would cannibalize more because they need more food to keep up with an increased metabolism. They also predicted that fall armyworms that eat an infected caterpillar would be more likely to become infected at higher temperatures.

Featured scientists: Kale Rougeau from Louisiana State Univerasity

Flesch–Kincaid Reading Grade Level = 7.3

Additional teacher resources related to this Data Nugget include:

You can also watch a time-lapse video of Kale in the lab to get a glimpse of their work. Follow along as they check fall armyworm cadaver samples for baculovirus infection using a microscope
Kale also provided a video of baculovirus lysing, where occlusion bodies that encapsulate the virus are dissolved, confirming the presence of infection in the fall armyworm sample.
  • Read more about Kale’s hobby of participating and training for dog competitions on the Beyond the Bench blog.
  • More about fall armyworms here and here.
9.23.24

Did you hear that? Inside the world of fruit fly mating songs

The activities are as follows:

Communication comes in all forms – through sound, smell, sight, touch, or even taste. The purpose of communication is to share some form of message or information to another organism. One form of communication between humans is talking, which is when we make a variety of noises as we speak using language. Just like people, animals make all kinds of noises to communicate with one another.

The tiny fruit flies that live on the ripe banana in your kitchen communicate as well. They use a courtship song when they are ready to mate. The male fly shakes his wings to sing a song to the female fly. The female fly hears the song, her brain processes the sound, and then she responds. Her brain decides whether she likes him or not. She may then try to kick him away or let him get closer.

Emma is a neuroscientist who is really interested in studying how brains are able to understand all kinds of communication. She uses fruit flies to figure out how brains process communication through sounds. Even though the fly brain is very small, they work a lot like human brains, so studying tiny flies singing to each other can help us understand our own brains.

While researching what other scientists had already learned about fly song, Emma read studies that described an interesting behavior called chaining. Chaining is a behavior when males chase and sing to each other. The scientists first observed this behavior when they played a fly song through a speaker for a group of 6 male flies. Emma wanted to see if she could repeat this behavior in her own lab. An important part of science is repeating experiments to make sure the results are accurate and can be achieved again and again. Repeating experiments can also be a way to test that another scientist’s methods work in your lab.

Sound is played through the yellow speaker. Flies are put into the chambers and watched for chaining

There are lots of things in the lab environment that can impact how a fly reacts to a song. Emma wants to pick a few variables to test. The first variable she selected is the volume of the courtship song being played. Emma decided to test different volumes to see how loudly she should play the fly song to get a response.

Since Emma couldn’t ask the flies if they could hear the sounds she played through her speaker, she measured chaining behavior instead. If the flies heard the sound from her recordings, she expected to see more chaining behavior.

Volume isn’t the only variable she can explore though. Imagine you are listening to a song and the singer sings a word you haven’t heard before. Do you think you’d be able to understand the word? The same thing may apply to the flies. Emma wanted to know if flies would react differently if they had been around other flies that sing. To test this, Emma raised some flies alone and others in groups. That way, she could see if being around other flies before the test made the song easier to recognize.

To gather her data, Emma put 6 male flies into a chamber with a clear top. She placed the chamber in front of a speaker. She also set up a camera to take a video of the flies for a minute before the song played and for a minute after the song began. This two-minute video allowed her to compare the flies’ behavior in silence with their behavior when the song plays. Then, Emma watched the video back and counted the number of flies that were chasing each other every 3 seconds. She did this for one whole minute (20 observation points) to get a chaining index for each group of flies.

Featured scientist: Emma Droste (she/her) from North Carolina State University

Flesch–Kincaid Reading Grade Level = 7.2

Students can listen to this audio clip of fly song and think about what these sounds may be communicating. The audio clip was generated by having a mating pair directly over a very sensitive microphone to capture the audio since it is not audible to the human ear.