Bubble mucus may not be the most attractive living space, but for some frogs, it is a refuge for drought. Amphibians usually lay eggs in pools to provide water for development, but these pools may dry up. “The biggest cause of mortality in frog offspring is dehydration,” said John Gould, an ecologist at the University of Newcastle.
When Gould studied frogs in the vatagan mountains in Australia, he was surprised to find that eggs in evaporated puddles had multiplied there for several days. The eggs were wrapped in their mother’s nest and secreted mucus with their toes. “You can see that the embryo is still alive and beating,” he said.
Scientists have previously hypothesized that frogs and Toad species use foam to protect their eggs from dryness, but few studies have verified this idea. Therefore, Gould and his colleagues monitored 641 mucus nests built by the sandpaper frog lechriodus fletcheri to determine whether embryos could survive in dry mountain conditions. They also conducted the first laboratory experiment to closely track the development of eggs in nests without water.
The team found that if the embryo of the wrapped embryo was protected by frothy frog foam, the embryo could indeed develop successfully in a dry pool. In some nests stranded on dry land, embryos can even endure well after full development until the rain replenishes a pool and some successfully hatch into tadpoles. Gould said: “bubble nest is almost like a life support system to maintain the viability of eggs.” He also found that larger nests provide more protection, and eggs close to the core can survive longer. This new work is described in detail in ichthyology and reptilology.
Elisa Barreto Pereira, an ecologist at the Federal University of Brazil, who was not involved in the study, said that with climate change, the bubble nest is crucial to helping frogs survive. “Bubble nest is an important adaptation,” she said. When the earth’s average temperature reached its peak 55 million years ago, the bubble nest evolved several times on different frog populations and continents.