A bizarre frog that breeds inside trees and lays eggs for its tadpoles to eat has been rediscovered in northeastern India after 150 years.
Last recorded in the wild in 1870, Jerdon’s tree frog was feared extinct until scientists found it during a three-year search that began in 2007.
The 20-inch (50-centimeter) long species was first discovered in the Darjeeling region by British zoologist Thomas Jerdon, who inspired its name Polypedates jerdonii. (See "'Extinct' Toad Rediscovered in Ecuador.")
But according to a new study, the long-lost amphibian actually represents a completely new genus—earning it the new moniker Frankixalus jerdonii.
Scientists observed the frog hiding in hollow bamboo stems and tree holes, where it carries out its remarkable breeding antics.
Females attach their eggs to the insides of tree hollows, which hold pools of water. When the tadpoles hatch, they fall in the water, where the females feed them unfertilized eggs until they turn into froglets. Most tadpoles of other frog species eat plant material.
The frog's DNA, odd feeding behavior, and anatomy shows the species “represents a deep evolutionary split in tree frog evolution,” says study co-author Ines Van Bocxlaer, of the Amphibian Evolution Lab at Vrije Universiteit Brussel, Belgium.
University of Delhi biologist Sathyabhama Das Biju, whose numerous past finds include India’s purple frog, led the expedition. (Related: “Weird Purple Frog Seduces Females From Underground.”)
In the East Khasi Hills district of Meghalaya state (map), the team found the tadpoles each contained up to 19 frog eggs. “It’s very clear that they are feeding purely on their mother’s eggs,” says Biju, who's nickname is the "Frogman of India."
He suspects females make return visits to the tree holes to keep their tadpoles topped up with eggs. (Also see "How Female Frogs Get Tricked Into Choosing An 'Ugly' Mate.")
Though the team didn't observe these food drops, Biju notes that females have an unusual, tube-like extension to their reproductive organs that would allow them to lay eggs one at a time.
“Another possibility could be that the female remains at the nest site,” says Biju, whose study appeared January 20 in the journal PLOS ONE. “In one instance, our study found a female submerged inside the water containing tadpoles.”
Since some breeding hollows were used by more than one female, a community of frogs may be sharing the burden of keeping their young supplied with meals—something that would need to be confirmed by future research.
James Hanken, curator of herpetology at Harvard University’s Museum of Comparative Zoology, says in an email that F. jerdonii's egg-feeding parental care is “very rare among frogs.”
“That being said, it’s evolved independently at least two times ... it also occurs in very distantly related frogs of the New World tropics,” says Hanken, who wasn’t part of the study team.
He suspects Jerdon’s tree frog eluded scientists for so long because the species apparently no longer occurs where Jerdon discovered it, while the regions where it lives now are poorly surveyed by biologists. (Also see "14 New “Dancing Frogs” Discovered in India.")
In fact, the study team uncovered a second, unidentified species along the northeastern border of India and China that may also belong to the newly described Frankixalus genus.
“This part of southeast Asia, in particular, is poorly inventoried,” Hanken said. “I wouldn’t be at all surprised if additional species were discovered.”
Whether any such frogs also lay their young an egg for breakfast, we’ll have to wait and see.