Deep Roots, Cold Streams

Our work really began in the mid-1970s, when Stevan Arnold did his PhD research at HBS characterizing the behavior of plethodontid salamanders, especially Plethodon shermani (then called P. jordani). Steve's partner, Lynne Houck, is also an expert in amphibian behavior, and the two collaborated closely studying the system through about 2016. In the early 1990s, Lynne recruited two biochemists, Rick and Pam Feldhoff, into the team to study the pheromones these salamanders exchange during courtship.

Hilariously, Lynne and Rick met while sitting next to each other on a flight to Chicago — which Rick likes to retell as Lynne “picking him up on a plane,” spawning a roughly 25-year collaboration. The plethodontid system is a powerful model for understanding how animals communicate using chemicals and the molecular mechanisms of olfaction. We were graduate students in the Houck/Arnold and Feldhoff labs, respectively, and spent our summers at HBS taking part in this interdisciplinary work. We started our own labs around the same time, and recently we've been able to continue tackling the many questions that remain about these fascinating animals.

From our observations and those of other researchers who work extensively at HBS, such as Grant Connette, salamander sightings are becoming sparser as erratic weather creates more dry spells that the animals avoid. Multiple forest fires and logging efforts haven't helped.

More disturbingly, we've recently observed delayed development of pheromone glands in male P. shermani. Using samples collected in 2024, molecular analyses by OSU graduate student Paul Nicolosi show that the genetic program of the glands is distorted relative to 2013, with most glands now producing significantly less pheromone. We're unsure what consequences this may have for reproduction, but it's something we're now actively monitoring.

Our two-to-four weeks at HBS each summer have always been an annual focal point for our team. The samples and experiments from that short window are analyzed throughout the rest of the year, collectively producing dozens of manuscripts over the decades.

Far more importantly, the station is a remarkably stimulating space — immersed in natural biodiversity, living and working among immensely talented scientists from across the country. Some of my favorite memories are the random social gatherings in Valentine House. You never knew who you'd meet in the kitchen, but they were usually interesting and enthusiastic about science — a good foundation for a conversation.

Plethodontid, or lungless, salamanders are common throughout the southeastern Appalachians and are remarkable animals — with genomes carrying roughly ten times more DNA than humans — yet we understand surprisingly little about their basic physiology. Our PhD advisors devoted much of their careers to mapping the molecular foundations and behavioral consequences of the pheromone courtship system, which remains one of the most tractable models for understanding how pheromones evolve between species. In addition to continuing that work, we're expanding into more layers of their molecular biology and physiology.

Steve, Lynne, Rick, and Pam collectively trained many PhD and master's students at HBS, plus many undergraduates. From Karen's lab, graduate students Emily Gremling and Sun Lanzilli conducted research here in 2022. From Damien's lab, PhD student Paul Nicolosi and undergraduate Liam Johnson are working at HBS this summer, studying different aspects of plethodontid reproduction. Paul is also the 2025 recipient of the Bruce Family Scholarship in Herpetology through the HBS Grant-in-Aid program.

We plan to keep working on eastern salamanders for the long term — and to train students to appreciate and understand these animals. We hope some will choose to become the third ‘generation’ of salamander pheromone researchers.

In addition to studying the dysregulation of the pheromone gland in males and how females perceive the pheromones, we're currently sequencing multiple plethodontid genomes to learn more about their genetics and physiology.

One of our most memorable moments from graduate school, back in 2008, was helping Steve film hellbenders in the Davidson River. Karen didn't do a very good job as a supporting cast member because she couldn't stop laughing as Steve crawled next to the salamander along the shallow stream bed. You can find it on Steve's ‘Salamander Courtship’ YouTube channel, along with others he filmed in North Carolina over the years.