Armed with sensitive antennae and wide-angle compound eyes, bees have a sophisticated set of senses that help them search for pollen and nectar as they buzz from flower to flower.
However, new research reveals that bumblebees can employ another hidden sense that allows them to detect when a flower was last visited by another insect.
Professor Daniel Robert, an expert in animal behavior and senses at the University of Bristol, UK, has discovered that bumblebees have the ability to perceive the weak electrostatic fields that form when they fly near a flower .
“A bee has the ability, even without landing, to know if a flower has been visited in the last minutes or seconds, by measuring the electric field that surrounds the flower,” explained Professor Robert.
The discovery is one of the first examples of electroreception in air . This sense has long been known in fish such as sharks and rays, which can detect the weak electric fields produced by other fish in the water . Mammals that live in water, such as platypus and dolphins, have also been found to use electric fields to help them hunt for prey.
But instead of hunting fish, bees seem to use their ability to detect electric fields to help them find flowers that are likely rich in pollen and nectar.
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Bees develop an electrostatic charge because when flying they lose electrons due to the friction of the air with their body , which produces a small positive electrical charge. The effect is a bit like rubbing a balloon against hair or a sweater, except that the charge accumulated by bees is about 10,000 times weaker.
By comparison, flowers are connected to earth, a rich source of electrons, and they tend to be negatively charged. These electrostatic charges are believed to help bees collect pollen more easily. The negatively charged pollen sticks to the positively charged bee because the opposite charges attract each other. Once pollen attaches to the bee, it is also positively charged during flight, making it more likely to adhere to the negatively charged female part of a flower, known as the stigma.
But Robert and his colleagues wondered if there could be more to this interaction. When they put an electrode on a flower, they detected a current flowing through the plant every time a bumblebee got close in midair. Their study revealed that the oppositely charged flower and bee generate an electrostatic field between them that exerts a small attractive force.
To study whether the bees are aware of this electrostatic field, they offered the bumblebees disks with or without sugar rewards. The ones with sugar also had 30 volts of electricity flowing through them to create an electric field. They showed that bees could sense the electric field and learn that it was associated with a reward . Without the charge, the bees could no longer correctly identify the sugary disc.
Another group’s research published shortly after Professor Robert’s work showed that honey bees are also capable of detecting an electric field . But exactly how the insects were able to do it remained a mystery, prompting Robert to create the ElectroBee project.
By the
Robert has discovered that the fine hairs on the body of bees move in the presence of weak electric fields . Each of these hairs has nerves at its base that are so sensitive that they can detect tiny movements – just seven nanometers – caused by the electric field.
Professor Robert believes that when a bee visits a flower, it can cancel out some of the negative charge and thus reduce the electrostatic field that forms when bees approach. This change in electrostatic field strength could allow other flying bees to figure out whether a flower is worth visiting before they land, helping to save time and energy.
Other signals, such as changes in flower color and odor, occur in minutes or hours, while changes in electrical potential occur in seconds.
Robert and his team are now testing their theory that the electric field helps bees know which flowers to visit, counting bumblebees’ visits to them in a meadow this summer and measuring the electric fields around the flowers.
Their findings could help scientists better understand the relationship between plants and pollinating insects , which could prove crucial to improving the production of many vital fruit crops that depend on bees for pollination.
Professor Robert is also investigating whether bumblebees use their electrostatic charge to communicate to their nesting sisters the best places to fly for pollen.
But while bumblebees use their extraordinary sensory power to find food within a few miles of their nests, another insect is using another hidden sense to make much longer journeys.
In Australia, Bogong moths ( Agrotis infusa ) constantly flutter from various parts of the country and head towards the Snowy Mountains in the southeast. They fly for many days or even weeks to reach the alpine valleys of the highest mountain range in the country, sometimes traveling more than 1,000 km. Once there, the insects hibernate in caves above 1,800 m during the Australian summer, before making the return journey.
The only other known insect that has migrated so far is the monarch butterfly, in North America. But while the monarch butterfly depends in part on the position of the sun to navigate , the moths fly at night. Professor Eric Warrant, a zoologist at Lund University in Sweden, has been fascinated since he was a student in Canberra, Australia, with the way these insects, only a couple of centimeters long, accomplished such a feat.
The mystery of the moth
He suspected that the moths could use the Earth’s magnetic field to find their way, so his team tied the moths to a stalk that allowed them to fly and spin in any direction before surrounding them with magnetic coils to manipulate the magnetic field of the earth. Land.
For two years, the experiments failed. Although the moths appeared to be influenced by the magnetic field, they also used something else to navigate: their vision.
“It’s a bit like we’re going hiking,” said Warrant, who is trying to unravel how moths perceive Earth’s magnetic fields in his MagneticMoth project. that direction, a tree or the top of a mountain ”.
His research has already shown that moths check their internal compass every two to three minutes and continue to give a visual cue ahead . But what can insects see at night?
Further investigation revealed something remarkable. When Professor Warrant downloaded an open source planetarium program called Stellarium and projected the Australian night sky onto the moths, he discovered that they were using the stars.
“Very few animals have the ability to read the stars and use them to find, north, south, east or west,” said Professor Warrant. “We (humans) learned how to do it. Some birds do.”
But the bug eyes of Bogong moths indicate that they do not simply follow a guiding star. Rather they are sensitive to panoramic scenes.
“In the southern hemisphere, the Milky Way is much clearer than here in the northern hemisphere,” Warrant said. “It’s really a pale strip of light interspersed with very bright stars.” He believes the moths are guided, at least in part, to their cool alpine caves by the light of the Milky Way.
The discovery could also lead to the development of new types of navigation for our own species. GPS, for example, relies on a constellation of satellites that are vulnerable to disturbances. Professor Warrant believes that studying an insect capable of flying 1,000 miles to a cave using a brain the size of a grain of rice could help us find alternatives.
“Animals seem to solve complex problems with little material and little energy,” said Professor Warrant.
Artículo original
This article was originally published in Horizon, the EU Research and Innovation Magazine
