Sun compass on demand

Monarch butterflies are well-known for his or her annual long-distance migration, which takes them over a number of thousand kilometers from the north of the USA to their overwintering habitat in central Mexico. On their migration, the conspicuously orange-black-white coloured butterflies use sun data as predominant orientation reference.

But how is sun data processed within the butterfly’s brain? Previous research have already described cells that course of the solar azimuth. “However, we did not know these cells encode the sun throughout flight,” says Jerome Beetz from the Biocentre at Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany.

Until now, it was assumed that the sun compass at all times works—regardless of whether or not the bugs sit, stroll or fly. A group led by JMU researchers Jerome Beetz and Basil el Jundi exhibits within the scientific journal Current Biology that this isn’t the case and that the compass is established on the onset of flight: “Surprisingly, the nerve cells change their coding technique throughout flight, in order that the neural network represents the heading direction of the butterflies relative to the sun in a similar way to a compass. This only happens when the animals can control their own direction of flight.”

Butterflies in a flight simulator

How was this hole in information closed? The group led by Beetz and el Jundi measured for the primary time the neural activity in actively flying monarch butterflies and examined the affect of the animal’s orientation habits on the processing of sun data. Such measurements had beforehand solely been carried out in restrained butterflies.

The JMU researchers took benefit of a technical trick: “We tethered the butterflies to a freely rotatable rod in the center of a flight simulator, which enables the butterflies to actively choose a flight direction. The sun was mimicked with a green light spot. While the tethered butterfly was flying, we monitored the brain activity with ultra-fine microelectrodes.”

The experiments show: Active motion of the butterflies is critical to course of sun data as compass data within the butterfly mind throughout migration.

“Our results emphasize the importance of performing neuronal recordings in actively moving animals in order to understand how the brain solves complex orientation tasks,” says Beetz, who’s first creator of the publication in Current Biology. Other researchers from the Biocentre in addition to from the colleges of Lund (Sweden), Bielefeld and Texas had been concerned within the mission. The work was funded by the German Research Foundation (DFG).

Brain the dimensions of a grain of rice with superb talents

Beetz admires his analysis topics: “Our publication uniquely demonstrates that even a brain with the size of a grain of rice is a highly complex organ that enables insects to perform such amazing behaviors. With their brain, monarch butterflies manage the enormous migration by using an efficient internal compass. Such a long-distance migration without using modern navigation devices is hard to imagine for us, humans and this is one major reason that drives my fascination for these enigmatic butterflies.”

Next, Jerome Beetz and Basil el Jundi plan to research how the butterflies’ sun compass operates when the butterflies have entry to the pure sky than when merely utilizing a light-weight spot as reference for orientation. To do that, the neural recordings should be carried out in open air flight simulators.