Magnetic sensors found in ant antennae

From CSIRO Science Mail

Some ants use magnetic sensors to find their way.

Tiny magnetic sensors have been found in the antennae of ants. Ants may use these magnetic sensors to find their way from one place to another, similar to an in-built compass.

The ant being studied is a species called Pachycondyla marginata, which is found in the rainforests of South America. These ants migrate, moving from place to place depending on the season. This particular ant species migrates in a direction 13 degrees from the north-south axis of the Earth on average.

“Behavioral experiments suggest that ants can use the Earth’s magnetic field and the Pachycondyla marginata ants seem to take into account such information for migration,” says Jandira de Oliveira, a PhD student working on the study.

Jandira travelled from Brazil to Germany with the ants to work with researchers specialising in electron microscopy. They used beams of electrons on ultra-thin samples of the ants to observe the magnetic sensors.

The scientists found the magnetic sensors to be nano-sized iron oxide particles in the antennae, particularly next to an area called Johnson’s organ. Johnson’s organ is a bit of a mystery to scientists, but they have already discovered links between the organ and gravity and sound perception.

It seems that the magnetic particles are not produced by the ants in a biological process. Instead, it is likely that the magnetic particles come from dirt. “The ants we studied dwell in tropical soils that are full of very fine-grained iron minerals, so there is plenty of material available,” says Jandira.

The magnetic sensors in the antennae work by detecting the Earth’s magnetic field. Then, the sensors send the information via a signal from the nervous system to the brain.

It is important to note that not all ants navigate in the same way. For example, desert ants have evolved eyes that use sunlight patterns to navigate. “There are many different ant species, each one adapted to their habitat,” says Jandira.