The Gastric-Brooding Frog: A Remarkable Tale of Extinction
The Rheobatrachus, whose members are famously known as the gastric-brooding frogs or platypus frogs, is a genus of extinct ground-dwelling frogs native to Queensland in eastern Australia. This genus, comprising only two species, holds a unique place in the annals of amphibian history due to its extraordinary method of incubating prejuvenile froglets within the stomach of the mother.
A Unique Genus
The combined ranges of the gastric-brooding frogs spanned less than 2,000 square kilometers, with both species primarily associated with creek systems in rainforests at elevations ranging from 350 to 1,400 meters. The precise causes of their extinction remain shrouded in mystery, but factors such as habitat loss, degradation, pollution, and diseases may have all played a role.
Biologists have engaged in fervent debates about the taxonomic classification of the genus. While some classify them within Myobatrachidae under the subfamily Rheobatrachinae, others argue for their placement in their own family, Rheobatrachidae. Molecular genetics has positioned them as close relatives to Mixophyes.
The Lazarus Project
In a fascinating twist of scientific ambition, researchers from the University of Newcastle and the University of New South Wales initiated the “Lazarus Project” in March 2013. This groundbreaking effort aimed to resurrect the gastric-brooding frog through cloning. Embryos were successfully cloned, offering a glimmer of hope for the potential revival of this extinct species.
Extinction and Taxonomy
The southern gastric-brooding frog (R. silus) was declared extinct by the IUCN, with no sightings in the wild since 1981. Taxonomically, the genus Rheobatrachus has remained largely unchanged since its initial description in 1973. The frogs’ distinctive features set them apart from other Australian frog species, including their large protruding eyes, short blunt snout, complete webbing, and slimy bodies.
The common names “gastric-brooding frog” and “platypus frog” aptly describe these frogs’ unique reproductive and aquatic nature, respectively.
Southern Gastric-Brooding Frog (R. silus)
Discovered in 1972, the southern gastric-brooding frog was restricted to the Blackall Range and Conondale Ranges in southeast Queensland. This species exhibited distinct physical characteristics, with a medium-sized, dull-colored body. The females were larger than the males, and their habitat primarily included rainforests and wet sclerophyll forests.
Northern Gastric-Brooding Frog (R. vitellinus)
Discovered in 1984 and confined to pristine rainforests, the northern gastric-brooding frog was larger than its southern counterpart and featured a pale brown coloration. They were mainly found around fast-flowing creeks and streams.
Unique Parental Care
What truly set these frogs apart was their distinctive parental care. After external fertilization, the females swallowed the eggs or embryos, a behavior observed in few other frog species. The mechanism behind this unique reproductive strategy involved prostaglandin E2 and a suppression of stomach acid production.
Causes of Extinction
The extinction of gastric-brooding frogs is thought to be linked to the introduction of pathogenic fungi into their native habitat. Habitat loss due to logging, feral pigs, weed invasion, and chytrid fungus are also suspected culprits.
Although both species are listed as extinct, conservationists continue to monitor their status. The ongoing “Lazarus Project” holds promise for potentially resurrecting these unique amphibians.
In the end, the enigmatic extinction of the gastric-brooding frog leaves behind a legacy of mystery and scientific ambition, as researchers strive to bring these remarkable creatures back from the annals of history.