Toxic frogs hold fascination, scientific promise for USFSM researcher

One of three black and yellow frogs, Dendrobates leucomelas, at Dr. Edie Banner's teaching lab.

One of three black and yellow frogs, Dendrobates leucomelas, at Dr. Edie Banner’s teaching lab.

SARASOTA, Fla. (Aug. 7, 2015) – When not teaching organic chemistry, biochemistry and medicines of the rainforest, Dr. Edie Banner is “getting back to my biology roots” researching the strange and colorful frogs that range throughout Central and South American rainforests.

The brightly colored creatures are poisonous to varying degrees to dissuade predators. In some cases, their toxic compounds can paralyze birds and monkeys. Even today, the compounds find use in poisoned darts favored by tribal hunters.

Dr. Banner is curious about the biology and chemistry behind the toxins, which she thinks might someday unlock the door to helping people with Parkinson’s or other neuro-muscular diseases “control their tremors.”

Her lab and office, which overlook Sarasota Bay on the second floor of the USFSM Teaching Labs at Mote Marine on City Island, are festooned with reminders of her abiding interest – stuffed toy frogs and frog knickknacks, are easy to spot – but it’s the terrarium with three glistening, black and yellow frogs – Dendrobates leucomelas – that most captures visitors’ attention.

The little animals, which hail from Venezuela, are so shiny and brightly colored that they seem unreal – plastic toys – until one stirs and begins to climb a glass wall. Eight tadpoles and four fertilized eggs live in small plastic boxes under the terrarium.

Dr. Banner says her frogs lack toxicity thanks to a tame diet of fruit flies, moth larvae and springtails (a kind of cricket). They’re part of breeding program for educational exhibits. They also figure into her lectures about the rainforest and diversity of life there.

So impressed is Dr. Banner by the tropical ecosystems – and the scientific mysteries they harbor – that she has begun work on a proposal to bring up to a dozen undergraduate students to Costa Rica next summer for a weeklong “field work” exercise.

The excursion would provide an opportunity for students mulling careers in biology to experience actual field work, she said. Two weeks ago, she returned from a five-day stay to check out the research stations of the Organization for Tropical Studies to host the students. Administered by Duke University, the stations lie nestled in the dense Costa Rican rainforest.

By day, the students would plunge into the thicket – not before a thorough tutorial about snakes and other dangers that lurk – where they would observe, collect samples and ponder how life is interconnected and survives there.

By night, they would live a rustic existence in dorm-like bunkrooms with shared bathrooms. The facility is not without some creature comforts, such as electricity and WIFI reception, but it lacks air conditioning. The students would live mostly a communal life centered around work.

“I want them to experience life as a field biologist, not on Facebook or YouTube, but in the field,” she said. “I want them to be curious and ask questions about what they see and what life is like out there. How does life survive?”

The joint student-instructor excursion would mark the first for Dr. Banner after coming to USF Sarasota-Manatee a year ago.

Before arriving here, she taught a range of chemistry courses for 10 years at the University of Richmond (Va.), Murray State University (Ky.) and Florida Southern College. She earned her doctorate in chemistry at the University of New Orleans.

Born and raised in New Orleans, Dr. Banner developed a fascination for nature early on from her Scoutmaster father, who insisted she hike and go fishing to learn about the outdoors.

“When I joined the Girl Scouts, he made sure I joined a group that did lots of hiking and camping,” she said. “I’ve been like that ever since.”

As for her goals today, she wants to continue teaching and delving into the world of rainforest frogs, specifically how they acquire the toxins that seep through their skin. During her trip next summer, she intends to collect samples of frog “sweat” using specialized pieces of paper.

A kind of “catch-and-release” exercise, the process involves capturing the creatures by hand before they hop away and wiping their skin with the stamp-sized pieces of paper to collect the venom. The frogs only pose a danger if ingested or if their sweat enters the bloodstream through an open wound.

In addition to collecting sweat samples, Dr. Banner said she wants to observe the frogs’ feeding routine. She understands that diet plays a dominant role in providing the toxins, but she is curious about how it contributes.

Are the toxins derived from a single type of insect or several types in combination? Do the frogs’ enzymes, acting with one or several ingested insects, cause the toxins to form? Since insects are at root of the frogs’ toxicity, how is it that they aren’t harmed by eating them?

It might turn out that a certain insect is responsible for giving rise to the poisonous compounds and that the frogs simply capitalize on the bugs to create defense mechanisms. If that’s the case, a whole new avenue of exploration could open up for Dr. Banner and other scientists.

Her trip to Costa Rica would depart next summer and last about a week.

“The experiences I’ve had and shared with my students have made a difference in my teaching,” she said. “I love seeing my students make connections that just cannot happen in the classroom alone.”