How does a Fruit Fly Smell

CSIRO News: Fly VS Robot – the smell-off!

Fly and robot

Vince thought the wine smelled like a fresh Spring morning, while the E-Nose6000 thought it just smelled like springs.

Illustrated by Mike McRae

It’s not all that difficult to tell when your milk has gone off – just take a whiff! But how many people would enjoy smelling off food every day? Or using their nose to test air pollution? Sounds like a job for a robot nose.

In some ways, electronic odorant receptors – or ‘e-noses’ – work a little like our own sense of smell by detecting different chemicals wafting through the air. Yet that’s where the similarities end. The e-noses being researched by the CSIRO rely on the odour’s chemicals reacting with oxygen in a strip of metal oxide, while an animal’s smell receptors use a range of nerves to do the job.

As handy as they are, the ability for e-noses to tell some smells apart can’t match biology where the fruit fly is concerned. To improve the technology, CSIRO’s Food Future’s Flagship compared the two and came up with some interesting answers.

The olfactory receptors in fruit flies aren’t very specific, each detecting a number of different chemicals as they sniff the air. Nor are they more sensitive than the e-nose. Yet the variety of e-nose smell receptors, each working on its own, produces a broad range of sensitivities, which may give it an edge in describing complicated fragrances. For instance, the overall aroma produced by wine as it ferments can reveal a lot about how it will taste, allowing the wine maker to make improvements. Telling the difference between each chemical within a smell would require a discriminating nose but the e-nose makes this separation.

However, replicating the fly’s talent for smelling could prove tricky for engineers, who aren’t sure how the fly’s receptors work together to distinguish different smells. Learning how this happens could lead to significant improvements in the e-nose.

At least now we know the answer to one question. How do fruit flies smell? Quite well, actually.

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.