Fastest Evolution Clocked in Tiny Fish

Scale Eating Pupfish — This pupfish from San Salvador island is the only species known to eat scales from other fish.

(Image credit: Chris Martin, UC Davis)

Pupfish with unusual diets, like biting off the scales of other fish, show some of the fastest rates of evolution known, according to a new study.

The tiny fish can survive in salty desert waters, such as within Devil’s Hole in Nevada. Pupfish live throughout much of the Americas, and of the 50 species most look the same and have the same food source, eating algae and detritus, according to lead researcher Chris Martin, a University of California, Davis graduate student.

One of the exceptions lives in shallow salty lakes on San Salvador Island in the Bahamas. The scale biter lives here, as does another species that eats small snails and creatures known as clam shrimp. Other odd types of pupfish originate from the Yucatán Peninsula of Mexico, where one eats other fish and another lives on plankton (tiny floating animals and plants). Both are now extinct in the wild.

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Wynne was a reporter at The Stamford Advocate. She has interned at Discover magazine and has freelanced for The New York Times and Scientific American's web site. She has a masters in journalism from Columbia University and a bachelor's degree in biology from the University of Utah.