Reproductive plasticity revealed: Neotropical treefrog can choose to lay eggs in water or on land

May 19, 2008

When frogs reproduce, like all vertebrates, they either lay their eggs in water or on land – with one exception, according to new research by a team of Boston University scientists who discovered a treefrog (Dendropsophus ebraccatus) in Panama that reproduces both ways. The neotropical frog makes a behavioral decision to lay egg masses aquatically in a pond or terrestrially on the overhanging plants above a pond, where the newly-hatched tadpoles simply fall into the water.

The dual reproductive capabilities enable this species of tree frogs to choose the best environment for egg development avoiding either aquatic predators or the hot tropical sunlight that dries out the eggs. In two shady forest ponds the mating frogs laid terrestrial egg masses, as expected from previous research. In a third pond in an old gravel quarry without a forest canopy, the vast majority -- 76 percent -- of the eggs were laid in water, supported by aquatic vegetation. The remaining 24 percent were on leaves above the pond, although the mortality rate of these eggs was high due to the heat and lack of shade.

The study, “Reproductive Mode Plasticity: Aquatic and Terrestrial Oviposition in a Treefrog,” by BU graduate student Justin C. Touchon and Assistant Professor of Biology Karen M. Warkentin appears in the Proceedings of the National Academy of Science online this week.

To test if genetic differences made frogs lay eggs in water or on land, or if instead their different environments affected egg-laying choices, Touchon and Warkentin built miniature ponds in an open field and in the forest. When they placed pairs of mating treefrogs in the shaded ponds, the frogs laid eggs on leaves above the water. In unshaded ponds, however, frogs put most of their eggs in the water.

Although this frog is the first vertebrate discovered to show reproductive flexibility, Touchon and Warkentin emphasize that it is probably not alone. The way an animal reproduces has been viewed as fixed, since most aquatic eggs die on land, and terrestrial eggs drown in water. This little yellow treefrog shows us such inflexibility is not universal.

Thus, the evolutionary change from aquatic to terrestrial eggs -- which has happened many times -- may not be a dichotomous switch but instead represent movement along a continuum.

Touchon and Warkentin suggest that this treefrog “could represent an intermediate stage in the evolution of terrestrial reproduction, combining a retained ancestral capacity for aquatic development with a derived ability for terrestrial oviposition and development.” This discovery opens new avenues of research into the evolution of reproduction on land. The treefrog’s ability to vary where it lays its eggs might also help it cope with changes in its environment, improving its chances of surviving habitat clearing or climate change.

Source: Boston University

Explore further: Alaskan trout choose early retirement over risky ocean-going career

Related Stories

Water fleas genetically adapt to climate change

May 11, 2015

The water flea has genetically adapted to climate change. Biologists from KU Leuven, Belgium, compared 'resurrected' water fleas—hatched from 40-year-old eggs—with more recent specimens. The project was coordinated by ...

Recommended for you

Revealing glacier flow with animated satellite images

November 26, 2015

Frank Paul, a glaciologist at the University of Zurich in Switzerland, has created animations from satellite images of the Karakoram mountain range in Asia to show how its glaciers flow and change. The images of four different ...

Hubble captures a galactic waltz

November 26, 2015

This curious galaxy—only known by the seemingly random jumble of letters and numbers 2MASX J16270254+4328340—has been captured by the NASA/ESA Hubble Space Telescope dancing the crazed dance of a galactic merger. The ...

'Material universe' yields surprising new particle

November 25, 2015

An international team of researchers has predicted the existence of a new type of particle called the type-II Weyl fermion in metallic materials. When subjected to a magnetic field, the materials containing the particle act ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.