Scientists have deciphered the complete genetic instruction book of monarch butterflies. It is the first butterfly genome completed and the first of a long-distance migrating insect.
Within the butterfly’s genetic archive, neurobiologist Steven Reppert of the University of Massachusetts Medical School in Worcester and his colleagues found genes that may help the insects sense the position of the sun and navigate to fir trees in Mexico, where they spend the winter. Reporting in the Nov. 23 Cell, the team also notes that monarchs make more of certain small genetic molecules, called microRNAs, that are involved in building muscle, regulating temperature sensitivity and storing fat when in migration mode.
The 273 million DNA units that make up the monarch genome also include a complete set of genes for producing juvenile hormone, which summer butterflies use to kick-start reproduction. Migrating male monarchs use different strategies than females do to turn off the hormone, the team discovered.
Monarchs have genes similar to ones that silk moths use to sense mating chemicals called pheromones. Those genes may aid social interactions between monarchs in their wintering grounds, Reppert says.
The scientists also unearthed from the genome a gear previously thought to be missing from the butterfly’s daily, or circadian, clock, which helps the monarchs maintain a straight path.