Next Generation of Mosquito Experts Is Being Developed at Catawba College
March 25, 2015
The next generation of mosquito experts is being trained and developed on the campus of Catawba College. The process began in 2014 under the tutelage of Dr. Carmony Hartwig, Biology Department, Catawba College and Dr. Bruce A. Harrison, a retired former Medical Entomologist for the U. S. Army, and later, for the NC Department of Environment and Natural Resources (DEHNR).
In 1993, shortly after the Catawba College's Ecological Preserve was established, Dr. Harrison began research in the preserve with Catawba's Dr. George Drum, now a Professor Emeritus of Biology. Harrison's work with the DEHNR focused on tick and mosquito vectors that may transmit bacteria and/or viruses involved in human disease. By the end of 1996, Harrison and another DEHNR associate, Parker Whitt, had determined that there were 30 different species of mosquitoes in the preserve.
In 2014, fate put Hartwig in contact with Harrison, currently an Affiliate Professor at Western Carolina University. Hartwig joined Catawba in 2012 and had started research on the diversity of mosquitoes in the preserve with help from Harrison's son, Ryan, an Environmental Health Specialist in Forsyth County. With Hartwig's background in infectious disease, she sought the expertise of the elder Harrison, who not only had knowledge of the Catawba Preserve collections, but vast experience in mosquito identification. In collaboration with Harrison, Hartwig and her students identified 28 species of mosquitoes in the Fred Stanback Jr. Ecological Preserve in 2014, and noted a substantial change in species composition over the past 20 years.
Hartwig and her students are working with Harrison on mosquito diversity and natural history, not only identifying the mosquito species morphologically, but confirming their identifications through molecular typing of a conserved gene. By assisting Hartwig and her students, Harrison is integral in developing and training the next generation of mosquito experts.
"This is a great opportunity for us, and a fantastic research experience for our students," Hartwig explains of the collaboration with Harrison. "He has a passion and a natural talent for teaching and conducting mosquito research. His goal when he was here in 1993-96 working with Dr. George Drum, was to examine tick and mosquito populations and look at patterns of invasive species as well as track potential disease vectors in all of the state parks and preserves in North Carolina. He graciously shared his 1993-96 collection records with me and now we have those data to compare with data we have collected."
Harrison's earlier data gives Hartwig and her students a starting point for tracking changes. The land that is now called the Catawba College's Fred Stanback Jr. Ecological Preserve has changed dramatically in 20 years, just like some of the mosquito species populations that thrive there.
"It used to be mostly open field topography when Dr. Harrison was here earlier and now it's more of a seasonally inundated wetland or flood plain forest," Hartwig says. "Because of this, the differences we have seen between his species records and our records are likely because of changes in the plant succession in the Preserve.
"A few species have become more abundant compared with the previous records, others have declined in abundance, and in 2014 specimens were collected of four species not previously found in the Preserve. One of these new records represents an exotic invasive species, Ochlerotatus japonicus, which is clearly established but not very abundant in the Preserve, and likely present in surrounding suburban areas. The other three species are Aedes cinereus, Ochlerotatus hendersoni, and Psorophora mathesoni, which are considered uncommon in North Carolina." These four new records means a total of 34 mosquito species have been found in the preserve during both survey periods.
During the period of the 1993-96 surveys only 56 species of mosquitoes were known from North Carolina, and now there are 65 species recognized in North Carolina. This increase occurred because of extensive and widespread collections conducted across North Carolina by Harrison and Whitt until July 2011, when the state program was abolished. With Hartwig, her students, and oversight from Harrison, additional species may be found in the Preserve.
Hartwig notes that identifying mosquitoes is much more difficult than one might think. Most of the species identification that she and her students have done has been with a microscope because "you can't identify species with certainty using the naked eye."
To get the mosquitoes under a microscope, Hartwig and her students must first trap them, using a standard Center for Disease Control (CDC) light trap. Dry ice placed alongside the light trap emits carbon dioxide, which attracts the mosquitoes into the collection container.
When viewed under the microscope, Hartwig says the mosquitoes are "beautiful and complex," and their numerous body parts, which can vary ever so slightly from species to species, must be examined carefully before exact identification is possible. An examination entails a visual study of the proboscis, thorax, abdomen, wing scales, halters, and hind tarsi and legs. Minute details such as the presence and color of the scales on their heads, thorax, and abdominal segments are vitally important. If any one of these features is missed, one might misidentify a species.
The proboscis can tell you a great deal about the type of feeder you may be examining. Some female mosquito species have a long proboscis that allows them to feed on the blood of birds; the long proboscis makes it easy for them to get through the bird's feathers. Both male and female mosquitoes feed on nectar; but, only the female mosquitoes feed on blood of humans and other animals. And, Hartwig shares, even that's interesting because the females "need vitamins and different proteins from blood to assist in the development of eggs."
Certain species prefer to lay their eggs only in artificial and natural containers. Also, while most species in the Preserve feed on mammals, others feed on birds, reptiles, and/or amphibians. One species, Toxorhynchites rutilus, is predatory in the larval stage on other mosquito larvae and serves as a natural control measure.
A mosquito's stages of development, Hartwig notes, are as interesting as what they feed upon or where they breed. When eggs hatch out in water as larvae they go through four molts, or instars before they develop into pupae. Pupal development is rapid and adults will start to emerge after only 3-4 days. How their eggs are laid, how the larvae gain nutrients and ‘breathe', as well as how eggs, larvae, and sometimes adult stages overwinter, can vary drastically depending on the species.
"It's cool to think how much species diversity we have in one spot," Hartwig says. With the combined data there are at least 34 confirmed mosquito species in one small 189-acre preserve; this is 52 percent of the 65 species found in the entire state.
"I feel fortunate that my students and I have the ability to do this sort of basic biological research every year. We're involved in a comprehensive observational study that will provide us with a valid record of mosquito populations temporally and spatially. Now that we have this database to work from we can branch out with investigations into the biology and behavior of individual mosquito species. For my students, it's not just field biology, but also molecular genetics, and they're acquiring many biotech skills that can be applied immediately to the work world. They are also gaining ample experience by presenting their work to the scientific community at several meetings throughout the academic year – not many undergraduate students can say that they have presented at a professional meeting or contributed to a manuscript. With Dr. Harrison's assistance I am hopeful that we will publish some of our collaborative findings this year."
Students assisting Hartwig with her mosquito study include three seniors, Joshua York, Elizabeth Brown, and Hugh Smith, junior Shannon Garrick, and two rising sophomores Ashley Wagoner and Hannah Przelomski. After three of her six students graduate, Hartwig will depend on Garrick, Wagoner, Przelomski and other student interns to help provide continuity with the work that will add to the mosquito knowledge base in Catawba's Preserve, as well as North Carolina.
Hartwig and Harrison anticipate that this collaborative work will find additional mosquito species not previously found in the Preserve. The detection and study of such diverse faunal groups is essential for understanding and evaluating the health and wellbeing of preserves. Although mosquitoes are usually thought of in a negative manner, they are extremely important in the food chains of birds, aquatic insects, fish, amphibians, immature reptiles, and in the overall health of the Fred Stanback, Jr. Ecological Preserve, which is a very diverse and unique natural area that will continue to provide vital information and facilitate faculty and student research for many years to come.