Zebrafish 'Erase' Their Stripes

Zebrafish are easily recognized by their characteristic stripes, for which they are named, and now researchers explain how they can just as easily "erase" them, a new study says.

The study, published in the journal Nature Communications, helps scientists better understand the genes and cell behaviors involved in producing pigments that give rise to zebrafish stripes. This, in turn, could help explain the mechanisms of pigment cells in humans and other animals, which can lead to skin disorders such as melanoma and cell regeneration.

"Using zebrafish as a model, we're at the point where we have a lot of the basic mechanisms, the basic phenomenology of what's going on, so we can start to look at some of these other species that have really different patterns and start to understand them," David Parichy, a corresponding author with the University of Washington, said in a statement.

Zebrafish are small, tropical freshwater fish native to the streams of the southeastern Himalayan region. These popular aquarium fish owe their name to the beautiful striped blue and gold pattern they adorn. Nature World News previously described how zebrafish get their characteristic colors, and now this latest study gives surprising new insights about how they can lose their stripes.

There are three pigment cells that make the zebrafish pattern: black cells, reflective silvery cells, and yellow cells. Then there are sometimes orange colors produced from cells called xanthophores, which, contrary to previous belief, come from pre-existing embryonic cells rather than stem cells. Thyroid hormone is what drives the appearance of orange-producing xanthophores - a hormone that also turns tadpoles into frogs, suggesting that xanthophores undergo their own metamorphosis. It turns out that in another species, the pearl danio, a certain gene causes the unusually early appearance of xanthophores - independent of thyroid hormone.

Unlike zebrafish this species lacks stripes, instead sporting a uniform pearly orange color.

The researchers were curious about this gene's role in zebrafish as well, so by expressing this gene the same way in the lab, the team forced the fish to make extra-early xanthophores. As a result, the zebrafish essentially "erased" their well-known stripes and donned a uniform pattern like the pearl danio.

This part of the study, described in detail in the journal Science, shows that timing really is everything.