Researchers Measure Neural Activity in Japanese Honeybees Using Hot Defensive Bee Ball Technique

Posted on March 16, 2012

Researchers have measured the brain activity in Japanese honeybees while they were using the hot defensive bee ball technique to kill an invading Asian giant hornet. The Asian giant hornet is a fierce predator of honeybees. It is also the world's largest hornet with a 2-inch body and 3-inch wingspan. The bees have developed a novel defense mechanism against the hornet. They create a hot bee ball by swarming around the hornet and literally cooking it alive.

For the experiment, the researchers presented an Asian giant hornet on a wire to the beehive. The bees came out of the hive and formed a hot defensive bee ball around the giant hornet. The bee ball was moved to a glass beaker. The hornet was dead about an hour after the hot defensive bee ball was formed.

The bee ball defense requires precision and coordination. The bees need to get the temperature inside the bee ball to at least 46 degrees Celsius in order to kill the hornet. However, they can't go over 46 degrees or the bees themselves will die.

A new study published here in PLoS ONE uncovers some of the neural activity that underlies this unusual behavior. The Japanese honeybee's European relative is unable to perform this bee ball defensive technique.

The researchers, including Takeo Kubo of the University of Tokyo and Masato Ono of Tamagawa University, sampled honeybees as they were engaged in a hot defensive bee ball. The researchers plucked them off the ball at different time points to investigate the brain function behind the unique adaptive behavior. Using a novel marker gene to detect the neural activity evoked in the brains of the honeybees that form the bee ball, they found that neurons that make up the higher brain center are active while the bees are part of the hot ball. This neural activity differs from that seen in European honeybees.

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