World's tiniest fanged frogs lay their eggs on leaves and guard them

The discovery of the world’s smallest fanged frog in Indonesia marks a significant addition to the diverse array of amphibian life. 

This new species challenges our understanding of frog biology, particularly in terms of physical adaptations and reproductive behavior.

Bony fangs 

One of the most remarkable features of the Southeast Asian frogs is the presence of two prominent bony “fangs” on their lower jaw. 

These fangs are not merely ornamental; they play a crucial role in territorial disputes, mate competition, and even in hunting formidable prey like giant centipedes and crabs.

Diminutive size

Jeff Frederick, a postdoctoral researcher at the Field Museum in Chicago and the lead author of the study, conducted this research as a doctoral candidate at the University of California, Berkeley. He highlighted the diminutive size of the newly discovered frog.

“This new species is tiny compared to other fanged frogs on the island where it was found, about the size of a quarter,” said Frederick. “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.”

Biodiversity hotspot

The discovery was made on Sulawesi, an Indonesian island known for its diverse habitats and rich biodiversity. Frederick emphasized the unique ecological features of Sulawesi. 

“It’s a giant island with a vast network of mountains, volcanoes, lowland rainforest, and cloud forests up in the mountains. 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,” said Frederick.

Unexpected discovery 

The researchers’ journey through the jungles of Sulawesi unveiled an unexpected phenomenon: nests of frog eggs not in water, but on leaves and moss-covered boulders. This finding was peculiar since most amphibians lay their eggs in water to prevent desiccation. The terrestrial egg masses were found several feet above the ground.

“Normally when we’re looking for frogs, we’re scanning the margins of stream banks or wading through streams to spot them directly in the water,” explained Frederick. “After repeatedly monitoring the nests though, the team started to find attending frogs sitting on leaves hugging their little nests.” 

Guarding the eggs

Upon closer examination, the experts realized that the frogs attending these clutches were all male. This male egg guarding behavior is relatively rare among amphibians. 

The proximity of the frogs to their eggs enables them to coat the eggs with protective compounds, safeguarding them against bacterial and fungal contamination.

Unique reproductive behavior 

An interesting hypothesis by Frederick and his team relates the smaller fangs of these frogs to their unique reproductive behavior. 

In contrast to their relatives, which lay eggs in water and possess larger fangs for territorial defense, these leaf-nesting frogs may have evolved smaller fangs due to their terrestrial egg-laying habits.

The scientific name of the new species, Limnonectes phyllofolia, translates to “leaf-nester,” aptly describing their unique nesting behavior.

Valuable ecosystems 

“It’s fascinating that on every subsequent expedition to Sulawesi, we’re still discovering new and diverse reproductive modes,” said Frederick. “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 study is published in the journal PLoS ONE. 

Image Credit: Sean Reill

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