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 (PNAS) 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.
Ronald Rosenberg | EurekAlert!
Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University
Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017
25.04.2017 | Laser Zentrum Hannover e.V.
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
25.04.2017 | Physics and Astronomy
25.04.2017 | Materials Sciences
25.04.2017 | Life Sciences