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Research

Of Ants and Amber

Entomologist studies "dairy farmers" of the ant world

Professor LaPolla conducting fieldwork in French Guiana, on the northern coast of South America.
Professor LaPolla conducting fieldwork in French Guiana, on the northern coast of South America.

Some prize amber for its beauty. But for John S. LaPolla, an assistant professor in the Department of Biological Sciences, these chunks of hardened resin harbor a treasure-trove of information about ancient life-forms—as well as clues to how lineages of organisms have been distributed through time.

So when investigators discovered an unusual piece of Dominican amber a few years ago, they notified LaPolla. The tiny specimen inside it—a winged queen ant gripping a white mealybug in her jaws—belonged to the genus Acropyga, one of LaPolla's research interests.

The find, estimated to be 15 to 20 million years old, enabled LaPolla to identify a new species, Acropyga glaesaria (glaesaria means "of amber"). It also helped him to better understand the small, yellowish ants known for farming mealybugs—which function rather like dairy cattle.

"The queen was on her nuptial flight when she became trapped," LaPolla says of the fossil. "The mealybug would have been the founding member of a new mealybug 'herd' in the queen's new ant colony."

The Acropyga ant's behavior, which he dubbed trophophoresy (roughly translated as "carrying food") is part of a complex symbiotic relationship that may have originated as early as the Cretaceous period, between 144 and 65 million years ago.

The ants "milk" mealybugs for a sugary, nutritionally complete substance called honeydew. In turn, ants tend their mealybugs much as human farmers tend their dairy cattle, sheltering and protecting the herd in exchange for food.

"It's interesting to ask how that relationship evolved and whether or not the two groups coevolved," LaPolla says. "When a new species of ant evolved, did a new mealybug species evolve as well?"

He observes that the two groups have been in an intimate agricultural relationship for millions of years without any apparent problems. "Ants, and not just Acropyga, have developed all kinds of long-term agricultural relationships and novel ways of handling the problems often associated with such relationships," he adds. "Just think of the myriad problems we humans have with crop diseases and pests. There's a lot we can potentially learn from the study of Acropyga and other ants."

Biology major Jim D'Antonio works with Dr. LaPolla to identify some tropical ant species from Guyana.
Biology major Jim D'Antonio works with Dr. LaPolla to identify some tropical ant species from Guyana.

LaPolla says that one of his favorite research pursuits—finding and describing new ant species—could be called "discovery science." To those who see such pursuits as "19th century, Victorian-era science," he points out that millions of insect and other species have yet to be discovered. "The age of species discovery is not even close to being over," he says. "Every species has a story to be told that fits into the biodiversity puzzle."

Although he recently joined the Department of Biological Sciences faculty, LaPolla says he's already working with undergraduates on a recently completed, National Geographic Society-funded biodiversity survey that took place in Guyana last fall. He's also seeking students for various projects in partnership with colleagues at the Smithsonian Institution and the National Institutes of Health.

"Towson is an exciting place to teach and conduct research," he says. "I attribute that to the energy of the department and the emphasis placed on faculty-student collaboration."

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