The mystery behind an insect’s spotted pattern A leopard can’t change his spots but what if — with the help of scientists — he could swap those spots for stripes? The way animals develop specific color patterns has always been a mystery. Until now.
A team of researchers from the Howard Hughes Medical Institute at the University of Wisconsin at Madison is the first to uncover the key ingredients to explain this decorative process in a species of fruit fly, Drosophila guttifera. The group investigated how the fruit fly generates a complex pattern of 16 black spots on its wings. The results, which appear online in the April 7 edition of the journal Nature, could potentially apply to color patterns on larger animals as well.
The scientists thought that a morphogen protein may underlie the color patterns. A morphogen protein can govern how tissue develops and whether certain cells make pigments. The presence of this type of protein could help explain why animals have particular patterns. And when researchers inserted the gene linked to that morphogen into the fly’s genome, they were able to create flies with striped wings instead of spotted ones.
“We don’t know what the patterns mean for these rarely studied fruit flies, but we picked the species for the complexity of the decorative pattern on its wings,” says one of the study’s authors, Sean Carroll, a geneticist and evolutionary biologist from the Howard Hughes Medical Institute.
Although researchers have discussed potential explanations for the development of stripes and spots, this is the first study to pinpoint a pathway that elucidates how these color patterns emerge.
“We had a hunch that the spot formation may involve an already known gene called Wingless,” Carroll says. Previous studies have found that the Wingless gene has several functions in fruit flies, including early development of the wing structure as well as bristle patterning on the wing.
The group decided to focus on the activity of the Wingless protein, a morphogen that’s encoded by a gene known as Wingless. They found that late in fly development, the Wingless morphogen was produced and prompted cells in specific areas of the wing to make a dark pigment. These areas corresponded to the exact location of the 16 polka dots. To confirm that Wingless was generating the spotted pattern, the team inserted the gene into the fly’s genome, manipulating where it would be active on the wing. Carroll’s team was able to make new decorations, creating stripes instead of spots.
“Our study provides a model of how a complex pattern is built on an animal from the ground up,” Carroll says.
