Tobin Hammer of the ecology and evolutionary biology department, armed with a butterfly net and on a mission to catch some Heliconius eratos, headed to a field site in Gamboa, Panama in his fancy ride: his bicycle. After catching as many butterflies as he needed he hopped back on his bike and headed back to the research station in the hope to uncover the hidden, never before known secrets of: the internal bacterial composition of the three key life stages of a butterfly species. DUN DUN DUUUUN.
So did he do it? Did he make mission impossible into mission possible?
Image from Wikimedia Commons
Leading his team, the University of Colorado Boulder Tobin Hammer utilized powerful DNA sequencing methods to obtain information regarding bacterial communities within caterpillars, pupae and adults of Heliconius erato, aka the red postman butterfly (oh scientists and their overly complicated names). Bacterial DNA was collected from the caterpillar itself, pupa and butterfly stages of the red postman. After that they utilized the barcoding method which enabled them to identify the bacterial DNA sequences. The discovery displayed unexpected events that occur during metamorphosis. Results displayed the “internal bacterial diversity” of the red postman was reduced to half the original amount when it transformed from the caterpillar to the chrysalis. Interestingly, it doubled after the pupae changed into an active adult butterfly. According to Hammer, this discovery is crucial because colonies of bacteria occupying other insects have been known to have an impact on different aspects of the insect such as the nutrition of the host, defense (from parasites, predators, and pathogens), digestion and detoxification.
Image from Wikimedia Commons
“What we saw was that the microbial community simplified and reorganized itself during the transition from caterpillar to pupa,” Hammer said. “Then we saw the diversity double after the adult butterflies had emerged and began going about their business of feeding. That was a little surprising to us.”
Sooo does it even matter?
According to Hammer YES, YES, YES!
“Butterflies are ecologically and scientifically important, and their transformation from caterpillar to chrysalis to winged adult is one of the most remarkable phenomena of the natural world,” he said. “But almost nothing had previously been known about what kind of internal microbes they have and how they change over the butterfly life cycle.”
Furthermore, there’s a lot of concern in the agricultural community due to the ability of caterpillars to do damage to crops. This is another reason as to why it was essential to conduct a study on the microbial composition of the caterpillars. Many people are starting to consider the microbiome of insects as targets for pest control purposes (including insecticides). This is why it is crucial to have information regarding the specific bacteria they have and the function of the bacteria. The biggest question surrounding this matter is “what these microbes are doing inside caterpillars and butterflies to influence their health and behavior,” said Fierer, a fellow at the Cooperative Institute for Research in Environmental Sciences, or CIRES.
But why did they choose Heliconius eratos? The red postman? The ultimate factor that led researchers to select this specific butterfly was due to its source of food—pollen which is a rich source of amino acids. Because a majority of butterflies feed on nectar, they tend to have short lifespans that may last only days or weeks. Whereas the red postman has discovered a method to digest and later extract nutrients from pollen grains which allows the butterfly to live up to several months. Hammer believes that this special characteristic to this genus could have been regulated by its microbiome. Furthermore pollen feeding has shown to have resulted in a co-evolution amongst Helioconius and their favorite flowers, which make more pollen and reduced nectar. They also live longer to match the butterfly’s unique lifespan. Additionally, the caterpillars are more easily able to provide a greater amount of resources toward producing toxic compounds to protect themselves from predators. The adult red postman butterflies contain the same compounds which release cyanide when the butterfly is consumed.
As we continue to gain information regarding the bacterial sequences of different animals, we significantly widen our micro-level understanding of the ecosystem. The discovery of the bacterial sequences of the red postman butterfly has opened the door to a better comprehension of the functioning and structures of these spectacular creatures. So the next time you want to get information about the bacterial sequences of butterflies don’t worry, sometimes you can just grab a butterfly net, a bicycle, a whole bunch of butterfly DNA and just wing it.