Academic journal article Science and Children

Frogs without Tadpoles?

Academic journal article Science and Children

Frogs without Tadpoles?

Article excerpt

All tadpoles grow into frogs, but not all frogs start out as tadpoles, reveals a new study on 720 species of frogs to be published in the journal Evolution. The study, "Phylogenetic analyses reveal unexpected patterns in the evolution of reproductive modes in frogs," conducted by John J. Wiens, an associate professor at Stony Brook University, and his colleagues Ivan Gomez-Mestre from the Donana Biological Station in Seville, Spain, and R. Alexander Pyron from George Washington University, uncovers the surprising evolution of life cycles in frogs.

Roughly half of all frog species have a life cycle that starts with eggs laid in water, which hatch into aquatic tadpoles, and then go through metamorphosis and become adult frogs. The other half, according to the authors, "includes an incredible diversity of life cycles, including species in which eggs are placed on leaves; in nests made of foam; and even in the throat, stomach, or back of the female frog. There are also hundreds of species with no tadpole stage at all, a reproductive mode called direct development." For decades, it has been assumed that the typical mode (with eggs and tadpoles placed in water) gave rise to direct development through a series of gradual intermediate steps involving eggs laid in various places outside water. …

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