Biologists have discovered a new species of the terrestrially-nesting fanged frog genus Limnonectes living on Sulawesi Island, Indonesia. The species has the smallest adult body size among all Limnonectes frogs from the island — with a maximum snout-vent length of about 3 cm (1.2 inches).
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Limnonectes phyllofolia. Image credit: Frederick et al., doi: 10.1371/journal.pone.0292598.
Limnonectes is a large genus of fork-tongued frogs in the family Dicroglossidae.
The genus includes over 75 scientifically recognized species. They are collectively known as fanged frogs because they tend to have unusually large teeth, which are small or absent in other frogs.
They use their fangs to battle with each other over territory and mates, and sometimes even to hunt tough-shelled prey like giant centipedes and crabs.
Limnonectes species are distributed from India to China and Indochina, through the Thai-Malaysia Peninsula, and across the Sunda Shelf landmasses (Borneo, Sumatra, and Java), the Malukus, the Lesser Sunda island chain, parts of western New Guinea, and the Philippines.
Large-bodied species prefer fast rivers, while smaller ones live among leaf-litter or on stream banks.
“Fanged frogs are stunningly complex in their reproductive biology,” said Field Museum of Natural History researcher Jeffrey Frederick and his colleagues.
“For example, two Malay species, Limnonectes hascheanus and Limnonectes limborgi, exhibit terrestrial egg guarding by males in conjunction with nidicolous larval ontogeny: larvae hatch as free-living tadpoles yet remain in a nest guarded by the male, surviving solely on nutrients from the yolk sack.”
“Four species of Limnonectes from Borneo, Limnonectes kuhlii, Limnonectes blythii, Limnonectes ibanorum, and Limnonectes ingeri are ‘voiceless,’ lacking a vocal sack for advertisement calling.”
The newly-described species, named Limnonectes phyllofolia, lives on Sulawesi, a rugged, mountainous island that makes up part of Indonesia.
“Sulawesi is a giant island with a vast network of mountains, volcanoes, lowland rainforest, and cloud forests up in the mountains,” Dr. Frederick said.
“The presence of all these different habitats mean that the magnitude of biodiversity across many plants and animals we find there is unreal — rivaling places like the Amazon.”
“Limnonectes phyllofolia is tiny compared to other fanged frogs on the island where it was found, about the size of a quarter,” he added.
“Many frogs in this genus are giant, weighing up to two pounds. At the large end, this new species weighs about the same as a dime.”
To the research team’s surprise, Limnonectes phyllofolia individuals caring for the clutches of eggs were all male.
“Male frogs guard one or more clutches of eggs festooned to leaves or mossy boulders one to two meters above small slow-moving streams, trickles, or seeps,” they said.
“Such behavior isn’t totally unknown across all frogs, but it’s rather uncommon.”
They hypothesize that the frogs’ unusual reproductive behaviors might also relate to their smaller-than-usual fangs.
“Some of the frogs’ relatives have bigger fangs, which help them ward off competition for spots along the river to lay their eggs in the water,” they said.
“Since these frogs evolved a way to lay their eggs away from the water, they may have lost the need for such big imposing fangs.”
“It’s fascinating that on every subsequent expedition to Sulawesi, we’re still discovering new and diverse reproductive modes,” Dr. Frederick concluded.
“Our findings also underscore the importance of conserving these very special tropical habitats.”
“Most of the animals that live in places like Sulawesi are quite unique, and habitat destruction is an ever-looming conservation issue for preserving the hyper-diversity of species we find there.”
“Learning about animals like these frogs that are found nowhere else on Earth helps make the case for protecting these valuable ecosystems.”
The discovery of Limnonectes phyllofolia is reported in a paper in the journal PLoS ONE.
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J.H. Frederick et al. 2023. A new species of terrestrially-nesting fanged frog (Anura: Dicroglossidae) from Sulawesi Island, Indonesia. PLoS ONE 18 (12): e0292598; doi: 10.1371/journal.pone.0292598
