Losing the harlequin toad means losing potential medicines

Amphibian loss worldwide has been a cause for outcry by scientists. Now, researchers have a new reason to care about the extinction of frogs and salamanders: the loss of their poisons. A recent review by Rebecca Tarvin and Kannon Pearson reminds us how little we know about endangered harlequin toads and their poisons.

Of the 113 known species of harlequin toads of the genus Atelopus, most are in decline a fourth of them might already be extinct. Other animal toxins have proven useful for drugs, so if we lose the harlequin toad, we also lose potential pharmaceuticals useful to humans.  

“In Central America, there’s nine species of Atelopus, and seven of them have been assessed for toxin diversity and quantity,” said Tarvin, UC Berkeley assistant professor of Integrative Biology. “But the majority of the Atelopus species actually live in South America, where a minority of the studies have been done.”

“There are entire countries, like Bolivia and Guyana, where not a single species has been assessed. We don’t know of any reports of whether Indigenous people use them. We don’t know if they’re toxic or not. One of the takeaways from our paper is that by losing these animals, we’re probably losing some chemical diversity, as well. They have some toxins that are found nowhere else in the world.”

Tarvin mainly researches toxicity in animals from butterflies and shellfish to reptiles and amphibians. Many animals evolve to sequester toxins from plants or host toxic bacteria, all without suffering ill effects. Some harlequin toads have a novel origin of their toxicity – they host skin bacteria that produce toxins.  

“One of the very first research projects I did was with Atelopustoads in Ecuador, and I just love them,” said Tarvin, who also is assistant curator of herpetology at UC Berkeley’s Museum of Vertebrate Zoology. “But from a scientific perspective, there’s a lot that’s unknown, and they are a huge conservation concern. So, I feel like they’re kind of a priority. Some of the species are doing fine, but they were really hit hard by chytrid (a fungal disease). A lot of species were completely wiped out.”

Once these toads were commonplace but are increasingly rare, like so many other species and face the possibility of extinction. Ecuadorian graduate student, María José (Majo) Navarrete-Méndez who wasn’t involved in the current study has heard first hand accounts of the toad’s decline, 

“My grandparents lived in the countryside — they were campesinos — and they remembered that (the toads) were extremely abundant,” said Navarrete. “I started realizing that we are in a race against time, and if it is not me, and if it is not now — we still have them available, and we have the technology and the resources to study them — it might be too late later.”

Like many groups of animals, we could lose harlequin toads before we understand them and their chemical defenses very well if nothing changes. 

—By Zach Fitzner, Earth.com Staff Writer