These particular butterflies have never visited the site in Michoacan before—in fact, their grandparents were likely the last generation there—but somehow the orange and black beauties know exactly where to go.

Circadian clocks in the monarchs’ antennae and brain direct the butterflies in their migration, but researchers at UMass Medical Center wanted to dive deeper. “There must be a genetic program underlying the butterflies’ migratory behavior. We want to know what that program is, and how it works,” explains Steven M. Reppert, MD, chair of neurobiology.

So he and his colleagues sequenced the monarch’s genome. Nature’s newsblog reports:

The 273-million basepair genome is the first of any butterfly and is considerably smaller than—and quite different from—that of the commercial silk moth (Bombyx mori), which has 432 million basepairs, suggesting rapid evolution in the Lepidoptera group, which includes both butterflies and moths.

The entire study is published in a recent edition of the journal Cell.

Within those 273 million basepairs, an estimated set of 16,866 protein-coding genes, comprising several gene families, are likely involved in major aspects of the monarch’s seasonal migration, according to the UMass researchers. These genes influence all of the monarchs’ senses in order to navigate: visual input gathers clues from the sun; monarch-specific expansions of odorant receptors exist for long-distance migration; a full repertoire of molecular components exist solely to support the monarch circadian clock; additional molecular signatures orient flight behavior; and a variant of the sodium/potassium pump underlies a valuable chemical defense mechanism to fend off predators during the migration.

“Dissecting the genetic basis of long-distance migration in the monarch may help us understand these mechanisms not only in monarchs but more generally in other migrants, including migratory birds and sea turtles,” Reppert says.

Image: Sonia Carolina Madrigal Loyola/Wikipedia

According to a new study reported online on March 11th in Current Biology, reindeers don’t have the same internal clock that other animals do.

The circadian clock or rhythm is the roughly 24-hour cycle that drives most living things, affecting our sleeping, waking, body temperature and hormones. The circadian clock is responsible for jet lag and that feeling you had when the alarm went off this morning.

Circadian clocks are not only found in mammals, but also plants, fungi, bacteria and insects. (Last fall, Science in Action produced a story on how monarch butterflies use circadian clocks inside their antennae to find their way to Mexico each year. You can view it here.)

Daylight does adjust these rhythms, but it’s the internal mechanism that does the driving. Except in reindeer.

“In reindeer, it is this clock element that seems to be missing,” said Andrew Loudon of the University of Manchester and one of the authors of the study. Light seems to be doing all of the work.

Norwegian and British researchers studied reindeer living in Norway, over 300 miles north of the Arctic Circle. During parts of the year in the Arctic, the sun does not set; at other times, it’s just the opposite. It appears that reindeer have simply adapted to this light cycle.

Studying reindeers’ levels of the hormone melatonin, scientists found no internal rhythm, the levels simply responded to light and dark. “Our findings imply that evolution has come up with a means of switching off the cellular clockwork,” Loudon said.

The researchers say that the findings initially came as a surprise, but they now suspect that similar patterns will be uncovered in other Arctic animals.

Creative Commons image by Marius Fiskum