A Bolivian frog species returns from the dead | Science News for Students

A Bolivian frog species returns from the dead

Scientists feared a deadly fungus had driven the species extinct in the wild
Feb 26, 2019 — 6:45 am EST
a photo of a Sehuencas water frog

For a decade, scientists feared this species was extinct. Then they discovered five Sehuencas water frogs in Bolivia, including this female named Juliet. Researchers plan to introduce her to Romeo, a frog in captivity. Until now, Romeo was the last known survivor of his species.

R. Moore

Scientists feared this frog was extinct. No one had seen a Sehuencas water frog in the wild since 2008. Just one “lonely” survivor, nicknamed Romeo, remained in captivity. A fungal disease has been wiping out frog populations worldwide, and scientists suspected it had killed off this one, too. But after 10 years searching Bolivian mountain forests for the long-lost amphibians, scientists have finally turned up a tiny group of five.

“It’s just incredible,” says herpetologist Robin Moore. A herpetologist studies reptiles and amphibians. Moore is the communications director at Global Wildlife Conservation in Austin, Texas. He was among the scientists who announced the rediscovery of this species on January 15.

Sehuencas water frogs (Telmatobius yuracare) live only in the Bolivian mountain cloud forests, where the climate is moist and cool. And that’s where researchers found the five. Unfortunately, this frog’s native habitat also provides the ideal conditions for the growth of a fungal infection with an ungainly name: chytridiomycosis (Kih-TRIH-dee-oh-my-KOH-sis). Most scientists just refer to it (and the fungus that causes it) as chytrid (KIH-trid).

The disease has killed off most Sehuencas water frogs. It was believed to have eliminated them all. Why the five newfound animals survived remains a mystery. “It could be that this small population has immunity,” Moore says. A genetic difference might make them resistant to the fungus. Or there might be something special about their environment, such as an unusually warm patch of cloud forest.

It could also just be luck. “Many species of frogs that disappeared for years — decades in some cases — have been seen again later,” says Karen Lips. She’s an ecologist at the University of Maryland in College Park. For example, Ecuador’s marsupial horned frog was missing for more than 10 years. In December 2018, researchers announced they had rediscovered it.

a photo of a Sehuencas water frog swimming underwater
Sehuencas water frogs live only in cool mountain streams, where chytrid fungus easily grows. That makes scientists wonder how a lucky few survived.
R. Moore

Reappearances can happen for several reasons, Lips says. There might be changes in the frogs, the fungus or the environment. “The simplest explanation is that once most of the frogs are gone, the fungus declines,” she says. With fewer hosts to infect, the disease can die off, too. Any surviving frogs can then slowly rebound until, years later, one hops in front of scientists.

The five newfound Sehuencas water frogs raise hopes that even more are still hiding in the wild. They also offer researchers a chance to help the species recover. Scientists have taken the five back to the lab. There, the frogs will breed and make more frogs that can later be returned to the forest.

There’s currently no good way to get rid of the deadly chytrid fungus in the wild. So scientists are eager to study frogs that have survived exposure to the disease, Moore says. They could offer clues to how the animals pulled through.

Whenever a frog that scientists thought chytrid had killed off later reappears, “it’s just an opportunity to understand a little more about how this [disease] works,” Moore says. And, he adds, it’s an opportunity to bring the frogs back.

Power Words

(more about Power Words)

amphibians     A group of animals that includes frogs, salamanders and caecilians. Amphibians have backbones and can breathe through their skin. Unlike reptiles, birds and mammals, unborn or unhatched amphibians do not develop in a special protective sac called an amniotic sac.

breed     (noun) Animals within the same species that are so genetically similar that they produce reliable and characteristic traits. German shepherds and dachshunds, for instance, are examples of dog breeds. (verb) To produce offspring through reproduction.

chytrid fungus     A common shortened name for a fungus — Batrachochytrium dendrobatidis —  that can induce a lethal infection in amphibians, especially frogs. The formal name of the infection is chytridiomycosis.

climate     The weather conditions that typically exist in one area, in general, or over a long period.

cloud forest     One of the more threatened tropical ecosystems, these are mist-shrouded rainforests that can develop high up along the sides of steep volcanic mountains. Because they have traditionally been hard to reach, they have tended to maintain a rich diversity of species.

conservation     The act of preserving or protecting something. The focus of this work can range from art objects to endangered species and other aspects of the natural environment.

ecology      A branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.

environment     The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).

extinct     An adjective that describes a species for which there are no living members.

fungus     (plural: fungi) One of a group of single- or multiple-celled organisms that reproduce via spores and feed on living or decaying organic matter. Examples include mold, yeasts and mushrooms.

genetic     Having to do with chromosomes, DNA and the genes contained within DNA. The field of science dealing with these biological instructions is known as genetics. People who work in this field are geneticists.

habitat     The area or natural environment in which an animal or plant normally lives, such as a desert, coral reef or freshwater lake. A habitat can be home to thousands of different species.

herpetology     The biology of reptiles and amphibians. Scientists who work in this field are known as herpetologists.

host      (in biology and medicine) The organism (or environment) in which some other thing resides. Humans may be a temporary host for food-poisoning germs or other infective agents.

immunity     The ability of an organism to resist a particular infection or poison by providing cells to remove, kill or disarm the dangerous substance or infectious germ. Or, when used colloquially, it means the ability to avoid some other type of adverse impact (such as firing from a job or being bullied).

infect     To spread a disease from one organism to another. This usually involves introducing some sort of disease-causing germ to an individual.

marsupial frogs     A group of species that don’t produce free-swimming tadpoles. Their young develop from eggs into tiny froglets within a pouch on their mother's body. Scientists describe this as direct development.

native     Associated with a particular location; native plants and animals have been found in a particular location since recorded history began. These species also tend to have developed within a region, occurring there naturally (not because they were planted or moved there by people). Most are particularly well adapted to their environment.

population     (in biology) A group of individuals from the same species that lives in the same area.

species     A group of similar organisms capable of producing offspring that can survive and reproduce.

Citation

Press Release: Global Wildlife Organization. Romeo, O, Romeo!, January 15, 2019.