Brazilian treefrogs have adopted an unusual breeding strategy

In a new study published by PLOS, scientists have observed some unexpected breeding behavior among Brazilian treefrogs. 

The researchers found that Paranapiacaba treefrogs lay spawn in small pools of water inside the leaves of bromeliad plants that are located on the banks of a stream. The tadpoles hatch from the aquatic eggs in the leaf tanks, and then make their way into the nearby stream to complete development.

The study is the first to report this unusual reproductive strategy among frogs, which are also known as anurans.

Led by Leo Ramos Malagoli from the Universidade Estadual Paulista in Brazil, the researchers spent 11 years collecting data on the courtship behaviors, mating, spawning, and tadpole development of Paranapiacaba treefrogs. This little-known species is native to the Atlantic Forests of Brazil. 

The experts observed the males calling out from bromeliad ponds located on or over streams. Next, the females mated with the males inside of the leaf tanks and layed spawn there.

However, the researchers found that the tadpoles did not complete their entire development in the tanks. By at least the 26th stage of development, the tadpoles had managed to enter the neighboring stream.

The study authors theorize that the tadpoles must fall, jump, or get washed out of the tank to complete their development in a large body of water.

It is not uncommon for frogs to mate in leaf tanks, which offer a refuge out of the sights of predators and competitors. With other species, however, the frogs usually relocate to lay their eggs in larger water bodies or the tadpoles remain in the leaf tanks until adulthood. 

The developmental strategy used by Paranapiacaba treefrogs allows their tadpoles to grow in a safe location while escaping before limited food and space runs out in the small leaf tank.

According to the study authors, high summer rainfall in the Atlantic forests of southeast Brazil likely drove the evolution of this unique breeding strategy.

The study is published in the journal PLOS ONE.

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By Chrissy Sexton, Earth.com Staff Writer