Georgetown College. Georgetown University.

By Theodora Danylevich

In a room filled exclusively with white buckets quietly teeming with mosquitoes, Dr. Peter Armbruster works with a plastic tube dangling from his mouth. He approaches a bucket labeled “New Jersey.” Untying an improvised fabric opening, he inserts the tube into the bucket and deftly sucks several mosquitoes into the tip of the tube, which has a cloth barrier preventing his ingestion of the insects. Dr. Ambruster proceeds to knock the bugs unconscious with a few shots of carbon dioxide from a large canister that stands by the door, then lays the immobile, live mosquitoes under a microscope.

Who would have thought, up close, these mosquitoes could be so shimmering and attractive? Yet perhaps more importantly, why would anyone willingly harvest and cultivate buckets and rooms full of mosquitoes, mosquito larvae, and mosquito eggs? In Dr. Armbruster’s lab, located on the first floor of the Reiss Science Building at Georgetown University, he and his industrious researchers don’t ask why. They do, however, address important issues in ecology and evolutionary biology through their close study of the Asian tiger mosquito, Aedes albopictus.

Recognizable by the black and white stripes on its legs, Aedes albopictus has proven to be a uniquely tractable species of insect for scientists to study and research. Mosquitoes in general are straightforward to work with in the lab, with an easily reproducible breeding ground of shallow water and humidity. Dr. Armbruster, a professor in the Department of Biology, takes advantage of this by encouraging his beginning and prospective biology majors to study and analyze the development and life cycles of mosquitoes, as well as perform various experiments with the insects. Aedes albopictus’ relatively recent spread across diverse climates provides a natural experiment that researchers like Dr. Armbruster and his students can use to track climate-related evolutionary adaptations in the insects first-hand.

Arriving in Texas from Japan in 1985, Aedes albopictus has since spread up and down the East Coast, from Florida to New Jersey. Its preferred breeding ground in the U.S. happens to be the water that collects in used tires, making it easy to transport this mosquito just about anywhere. Dr. Armbruster, who had been set on saving endangered elephants as a graduate student, sometimes wonders about the different lifestyle that his research could have afforded him had he pursued an animal with a more exotic or scenic breeding ground. As it is, Dr. Armbruster and his researchers make frequent trips to junkyards up and down the coast, harvesting mosquitoes (and their larvae and eggs) from the moist insides of used tires.

Originally from a temperate climate in Japan and now inhabiting both temperate New Jersey and Florida’s tropical climate for several decades, Aedes albopictus has undergone physiological climate-related evolutionary adaptations that have been useful and fascinating for researchers. Dr. Armbruster and his more advanced students are most interested in one such adaptation called photoperiodic diapause.

Photoperiodic diapause is related to the female mosquito’s sensitivity to shorter versus longer daylight hours (photoperiodic sensitivity). When days are shorter, the photoperiodically sensitive female inhabiting a temperate climate lays eggs that are different from the eggs that she lays when days are longer. Eggs laid when days are shorter are dormant and do not hatch until the following season, ensuring the species’ survival through the winter. Photoperiodic dormancy is a critical evolutionary capability in Aedes albopictus as well as a wide variety of plants and animals (think of hibernating bears). However, very little is known about the physiological and molecular bases of how the females actually process the shorter days in order to lay the dormant eggs and what it is about the eggs that actually makes them dormant.

The mosquitoes that have adjusted to Florida’s sub-tropical climate have partially shed their photoperiodic dormancy response, as it is no longer a necessary feature for their survival. Working with samples from the same species both with and without photoperiodic sensitivity allows Dr. Armbruster’s lab to use various experimental settings and research methods, including an emphasis on genetic analysis, to isolate the agents of photoperiodic sensitivity in order to gain an understanding of how this particular evolutionary adaptation works.

Keith Summa, a recent graduate from Georgetown College, spent the past summer in Dr. Armbruster’s lab wrapping up his research concerning two genes that scientists have reason to believe play a role in physiological reactions to day length. Using state-of-the-art equipment, Summa worked to isolate genes for analysis and data collection. This kind of genetic research involves a lot of trial and error.

“I must have gone through hundreds and hundreds of mosquitoes in the course of this project,” says Summa.

Summa and Dr. Armbruster are currently co-authoring a paper on this research, “Isolation and expression patterns of the circadian clock genes period and timeless in the Asian tiger mosquito, Aedes albopictus.”

“I value and enjoy working together with students,” says Dr. Armbruster, who is excited about another research paper also currently in preparation for publication, “Identification and expression patterns of three atypical OBP-like genes in the Asian tiger mosquito, Aedes albopictus,” co-authored with two other undergraduate students.

While learning about photoperiodic diapause does open the door to the eradication of mosquitoes in temperate climates, this is not Dr. Armbruster’s primary focus.

“We may ultimately be able to figure out how to disrupt photoperiodic sensitivity, and thus keep Aedes albopictus out of the temperate regions,” says Dr. Armbruster. “However, what keeps me interested in the system is not an agenda to eradicate the mosquito, but the fact that it is a very tractable system for addressing basic questions in ecology and evolutionary biology.”

As in all science, a rigorous understanding of minute processes goes a long way: Understanding the molecular details underpinning evolutionary changes in photoperiodic diapause of Aedes albopictus will help the scientific community to develop a more detailed and accurate understanding of general evolutionary principles that apply to a broad range of organisms—from ants to elephants and beyond.

Dr. Armbruster and his lab are aware of the environmental implications of mosquitoes in a university setting.

“We sometimes have escapees,” he says, “but we try to keep them at a minimum. We haven’t gotten any complaints yet.”

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