Could a new identified protein be responsible for animals’ sense of direction and their ability to find their way around?
Scientists from Peking University thought so. They discovered tiny biological compasses – made from protein structures – in fruit flies that also appeared in pigeon, rat, whale, butterfly and human cells.
Here’s how it possibly works: the protein compasses align with the geomagnetic field lines of Earth, leading scientists to conclude that these internal compasses feed information into the animals’ nervous system for a direction-sensing ability.
Lead author Professor Cam Xie said this compass can likely serve as a universal “animal magnetoreception” mechanism, which enables a diverse range of animals to navigate with the aid of Earth’s magnetic field.
The Chinese research team screened the genome of the fruit fly and discovered MagR, a protein with a rod-like clump structure with cryptochrome (retinal) proteins. This cluster functions like a magnetic sensor that can sense the Earth magnetic field’s direction as well as inclination or intensity.
“The nanoscale biocompass has the tendency to align itself along geomagnetic field lines and to obtain navigation cues from a geomagnetic field,” explained Xie.
It used to be an unpopular belief that animals could sense the magnetic field of the planet. Now it has been established among a number of species, although the mystery lies in how the sensing happens.
A kind of molecular compass senses geomagnetic field data through electrons’ quantum behavior, which is created when light falls on cryptochromes. Xie, however, argued that there is more to navigation than a cryptochrome-based compass.
The MagR-cryptochrome compass was found by the team to form in different species including pigeons, monarch butterflies, minke whales, rats and humans. The compasses’ role in human navigation remains unclear due to the intricate nature of human directional sense, but Xie said the same concept could explain some individuals’ good sense of navigation.
Quantum materials researcher Simon Benjamin from Oxford University pointed to evolution’s way of sensing magnetic fields, and thought it possible that the protein structure is key in the compass of the fruit fly and other species.
He highlighted the MagR-cryptochrome cluster’s potential use in developing new technology. “There is a continual drive for cheaper, smaller, more robust or more sensitive field sensors,” Benjamin said, citing their use in processes such as mining survey systems.
Magnetic sensing expert Professor Michael Walker from the University of Auckland in New Zealand, however, deemed the findings “a very tentative suggestion” and said the evidence presented is in vitro instead of in animals.
"There is no evidence that the correct conditions for the formation of the protein complex actually exists in the eye of animals," he argued, instead preferring the magnetite hypothesis: creatures navigate using magnetites or crystals of an iron oxide found in nasal cells.
According to Walker, natural selection would make having more than one biological compass improbable.
The findings were published in the journal Nature Materials.
Photo: John Tann | Flickr
