The butterfly, the fruit fly and the quantum robin (pt. 1)

Monarch butterflies navigating the world (and fruit flies too!)

1. Butter(flies)

Every year, millions of butterflies fly from southeast Canada to high mountains in Central Mexico, and then all the way back. Notably, the butterflies who fly back are not the same ones who flew there - but their grandchildren instead. The antennae of butterflies contain the pigment cryptochrome, which are essential for their circadian clock. 

Some evidence we have: in mutant fruit flies, scientists replaced their defective cryptochrome genes with the monarch butterfly’s functioning cryptochrome genes, restoring the flies’ circadian sense. 

Magnetoreception is the animal’s ability to detect the earth’s magnetic field. In 2008, it was theorized that the cryptochrome that allowed the flies to have the light sensitivity necessary for their circadian rhythms might also be behind their magnetoreception. An experiment was designed in which the fruit flies were trained to follow the magnetic field down a maze to get a sugary reward instead of the alternate path, which had nothing. The fruit flies with a mutated cryptochrome gene were equally likely to follow either path, indicating that cryptochrome was necessary for their magnetoreception. 

2. Robins

Earth’s magnetic sphere protects our atmosphere from being torn away by solar winds, but it is very weak. Despite this, it appears that many animals are able to navigate with the help of the magnetic field, including sea turtles, rainbow trout, and microbes. There were two theories as to how animals do this, and it was thought that both were present across different species. 1) magnetoreception is like a magnetic compass, 2) magnetoreception is like a chemical compass. 

The first was disproven pretty quickly, so scientists begun testing the second. One early study in 1963 captured robins (that migrate between Europe and North Africa, assumedly using the magnetic field). They were exposed to an artificial magnetic field generated by a Helmholtz coil, and they had a tendency to try to move towards the side of the chamber that had the magnetic field that would be the same one corresponding to their migration route. The mystery persisted: the birds lost their ability to navigate when they were blindfolded. Why?