Carp Have Gotten Their Scales Back After Medieval Monks Removed Them

August 24, 2016 | Erica Tennenhouse

Common carp
Photo credit: Public Domain

The scales of carp in Madagascar, which were bred out by monks, are returning through a new genetic pathway.

Medieval European monks had the bright idea to selectively breed carp without scales, in order to make them easier to prepare for meals.

These mirror carp — so-called because of their smooth, reflective surfaces — were released into the waters surrounding Madagscar, where carp had previously been absent, around a century ago as a food source for the people living there. Their population rapidly took off, and by the 1950s, people began to notice that those scales were making a comeback.

Now, researchers examining the scales and DNA of 700 carp caught in Madagascar have found that 65 percent of the fish have regained their scales. But incredibly, these scale-covered fish still carry the mutated gene that originally caused their ancestors to go scale-less. Rather than reverse that mutation, the carp have used a completely different genetic pathway to re-evolve their scales in fewer than 40 generations.

Like a suit of armor, scales provide protection from predators and parasites for otherwise soft-bodied fish.

The study was published in the journal Biology Letters.

Read next: Flexible Fins Allow Fish to Climb Trees

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