Darwin's frog, named in honor of Charles Darwin, is an endemic species of the southern forests of Chile and Argentina, which is also classified as Endangered. Unfortunately, in the last decade, their populations have experienced an 80% decline, primarily attributable to the Chytrid fungus, responsible for a disease that affects both the skin and the cardiac system of amphibians, in addition to the critical state of the forests.
"The female generates eggs inside her body, like all amphibians, and then, together with the male, the amplexus or nuptial embrace occurs, which is when the male embraces the female, and she releases the eggs, and the male fertilizes them at that moment."
Often, most amphibians leave the eggs where they were and leave them tied in the gelatin or water to develop, but not in the case of Darwin's frog. The female deposits the eggs on the forest floor and leaves, never to return, so that the male remains with them.
The male stays around the eggs for about two weeks, and when signs of tadpole activity begin, the father swallows them and stores them in a vocal sac located below his digestive system. This process is called neomelia. The exact number of eggs he can hold is not known, but records exist of between 10 and 14.
He stores them there for six to eight weeks, and during that time, he does not eat, only caring for the young, who feed on the reserves left inside the egg, thus the function is not nutrition, but protection.
"The interesting thing is that they emerge as small adult frogs, meaning they undergo the metamorphosis process inside the male's vocal sac, who then goes through a birthing process, so to speak; he swallows them, gestates them, and protects them for a time."
The male's role is crucial for the gestation and reproduction process of the small tadpoles; while the female provides many nutrients and energy, the care of the process is carried out by the male, something that is usually very associated with females in the animal kingdom. Moreover, "no other species is known to do something of this nature."
There are other amphibians with similar, but not identical, processes," he noted. This makes it very striking, special, and unique in biology, representing an innovation that can be important for all lineages and, especially, for the sites where Darwin's frog lives.
On the other hand, it is important to note that Darwin's frog is endangered. It is an endemic species of Chile and bordering areas of Argentina, inhabiting the Biobío and Los Lagos regions, with a length that rarely exceeds 5 centimeters.
Amphibians are the most threatened group of vertebrates in the world, according to a study published in the scientific journal Nature in early 2024, which included the critical analysis of more than 8,000 species and 20 years of global data. Among the results, it was detected that 160 amphibian species are considered "Possibly Extinct," including the Northern Darwin's Frog, which inhabited the coastal forests between Zapallar and Concepción and has not been seen since 1981.
"Thus, the southern Darwin's frog, which, like a good amphibian, is quite sensitive to environmental conditions and habitat changes, are not animals of great mobility and are very sensitive to the biochemical state of the exterior because they breathe through their skin."
Currently, several organizations have developed binational strategies for the conservation of Darwin's frog to reaffirm the commitment to its protection in Chile and Argentina.
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