Hormone still rules no-tadpole frogs

Skipping most of the tadpole business, a coqui frog hops out of the egg as a miniature adult, smaller than a pea. Even so, it doesn’t escape the king of tadpole chemistry, thyroid hormone, say Canadian researchers.

In most mainland U.S. frogs, a surge of thyroid hormone tells a tadpole to grow up into a frog shape. However, hundreds of other frog species, mostly in the tropics, have lost the tadpole stage.