Egg-sitting glassfrogs create safe exit for tadpoles

https://www.eurekalert.org/pub_releases/2017-03/stri-egc033017.php

Public Release: 31-Mar-2017
Egg-sitting glassfrogs create safe exit for tadpoles
Smithsonian Tropical Research Institute

Glassfrogs may be somewhat see-through, but they have still managed to a hide an important secret--they are dedicated mothers and fathers that invest time in brooding their eggs. Smithsonian scientists documented previously unknown parental-care behavior using detailed observations of 40 species of glassfrogs in Central and South America. Their discovery rewrites assumptions about how caregiving evolved in this family of translucent, tree-dwelling frogs.

"These are relatively well-studied, charismatic frogs, yet we were fundamentally wrong about their reproductive behavior," said Karen Warkentin, associate scientist at the Smithsonian Tropical Research Institute and professor at Boston University. That is because the frogs mate during the night, laying their eggs from leaves that dangle over running water. Warkentin's doctoral student, Jesse Delia, and research partner Laura Bravo-Valencia of the University of Los Andes, Colombia, had to adopt nighttime schedules to observe what the frogs were doing.
"Because Jesse and Laura were spending all night on the streams, they saw things that nobody had seen before," Warkentin said.

Crucially, Delia and Bravo-Valencia observed that female frogs will sit upon their eggs for up to five hours after laying them. The frogs' translucent bellies absorb water from dew-covered leaves, which they then use to hydrate the jelly-coated eggs. Swelling up to four times its thickness, the jelly protects the developing embryos from egg predators and fungal infections.

Previously, only males of some species of glassfrogs had been observed brooding eggs, leading researchers to assume that parental care was rare in the glassfrog family. But in a new study published in the Journal of Evolutionary Biology, Delia and his collaborators found that every species they observed cared for its eggs.

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