Rain frog

A species of rain frog called Pristimantis pluvialis is seen here. The frog was discovered recently in southern Peru by a team of researchers including Alex Shepack, a doctoral student at Southern Illinois University Carbondale, and Alessandro Catenazzi, assistant professor of zoology at SIU. Photo provided

July 29, 2016

SIU duo helps discover species of rain frog

by Tim Crosby

CARBONDALE, Ill. – Deep in Peru, amid the rain forests of the Amazon and on the foothills of the Andes Mountains, a secret was waiting.  And researchers from Southern Illinois University Carbondale are part of a team that recently discovered it. 

Years of painstaking research, much of it involving foot-treks along forest trails, creeks and ponds, often by light of headlamp, has resulted in the researchers identifying a new species of rain frog amid the teeming amphibian life there. The discovery of the new species – called Pristimantis pluvialis – is described in a recent article published in open access journal ZooKeys. The lead author is Alex Shepack, an SIU doctoral student working with Alessandro Catenazzi, assistant professor of zoology at SIU, who has worked in the area of the Amazon and Andes since 1996. 

The research team, which also included members from the University of Michigan and the National University of San Antonio Abad of Cusco in Peru, discovered the new species of rain frog in southern Peru, near the border of Manu National Park. The area is protected by law, and contains the highest number of species of amphibians and reptiles in the world. 

The team found several specimens of the new species during nocturnal surveys in the area. Researchers also collected specimens within the private conservation area Bosque Nublado, owned by the Peruvian non-governmental organization Peru Verde, and within the Huachiperi Haramba Queros Conservation Concession, the first of its kind granted to a native community in Peru. Researchers say the species is likely found within the park, and brings the number of known amphibian species in this area to 156. 

A member of the genus Pristimantis, the frog exhibits direct development, which means it is capable of undergoing its entire life cycle without a tadpole stage.  It also differs from other members of its genus by its call, skin texture, and other factors. 

Researchers gave it its name “pluvialis” -- coming from the Latin word “pluvial,” which means pertaining to or produced by rain -- based on the incredibly rain-soaked habitat where it lives, and because it was found calling only after heavy rains. 

The frog is superficially similar to other rain frogs, but researchers distinguished it by its morphology, call, and genetic sequences. The frog had been collected in the past, but because it seemed very similar to others, Catenazzi said he hadn’t been in a hurry to investigate it, as other specimens the team collected exhibited unique characteristics and kept researchers busy with species descriptions. 

“I have long suspected this might be a new species, but because it is very similar to other species, and because bioacoustic and genetic data were missing for many of these similar species, it wasn't a priority,” Catenazzi said. Ultimately, however, with the publication of more genetic data and advertisement call of similar species, the team was able to classify the frog as its own species. 

“Alex (Shepack) and I have been working in Peru since 2015, visiting field sites during the rainy season in January and the dry season in June,” Catenazzi said. “The field work involves walking along forest trails, creeks, ponds and such at night and using a headlamp to observe amphibians. Those that are potentially new we capture and collect for later analyses.” 

Catenazzi said Shepack was instrumental in the discovery. 

“Alex is doing his fieldwork at the locality where the new species was discovered, and he's directly involved in describing new species, which he needs to be able to identify for his own work,” Catenazzi said. 

The team also tries to record the sounds of the males’ “advertisement” calls when possible, in order to collect as much natural history information as possible about the habitat and behavior of their quarry. They take extensive photographs from many angles, check the sex of each specimen, measure them, note their coloration and collect other biological data, such as genetic analysis, among others. 

The researchers also looked at environment -- the coordinates where specimens were captured, temperatures there, as well as date and time of the encounter. Ultimately, they sacrificed some specimens and fixed them in preservatives as so-called “voucher specimens.” 

“New species cannot be described without voucher specimens, so it is absolutely necessary to collect and properly preserve a good series of adult specimens,” Catenazzi said. 

The discovery was a satisfying outcome for Shepack, a Morris, Conn., native, who has conducted scientific work in Central America for almost a decade. 

“I didn't begin working in Peru until I came to SIU in 2014,” he said. “(Catenazzi) has a long history of working down there, and I picked up helping him with his projects. Since coming to SIU I have made three trips to Peru and spent almost three months there.” 

Working in the rugged environment favored by the amphibians is tough, but rewarding, Shepack said. “Field work in Peru presents a whole suite of difficulties, but is extremely rewarding,” Shepack said. 

Much of Shepack’s research in Peru has focused on how the pathogenic fungus Batrachochytrium dendrobatidis has decimated the populations of amphibians. The pathogen appears to kill adult frogs by causing what is essentially a bad case of athlete's foot on their skin. While such irritation to human skin is an annoyance, to a frog it is deadly as they receive a large amount of oxygen and moisture directly through their skin. Electrolyte imbalance follows infection, which leads to cardiac arrest. 

The fungus has caused declines in other frog species and around the area where Shepack and Catenazzi discovered the new species. About 40 percent of the new specimens of the species they discovered also were infected, though its effect on this new species is unknown and its populations do not seem to have declined following the arrival of the disease in the early 2000s. 

With so much effort devoted to researching the deadly disease, making a discovery of a new species was a welcome change. 

“We were pretty excited,” Shepack said. “This is a very well-studied area, and is widely known as one of the most biodiverse with respect to reptiles and amphibians.  To still be finding new species is pretty awesome.” 

Shepack, who is a Morris Fellow at SIU, said doing research at the university will help him immeasurably as he pursues a career in science. 

“It's a pretty awesome experience to be able to describe a new species,” he said. “No matter where I end up next, I can always know that I've made an impact by helping to describe more of the world's diversity. SIU has been great in its support. Being a Morris Fellow allows me the flexibility to travel and do my research. Additionally, I am surrounded by an incredibly diverse -- with respect to research -- and supportive department.”