Infected bees found elevated levels of pheromone anxiety

Steve Bates / Flickr
Steve Bates / Flickr

Biologists have found an increase in the level of one of the components of pheromone anxiety in honey bees(Apis mellifera), patients with nozematosis. This disease is caused by relatives of fungi - microsporidi genus Nosema. Scientists believe that the high level of this substance can be more dangerous than the infection itself. The work is published in the journal Royal Society Open Science.

Many animals communicate with individuals of their species with the help of chemical compounds - pheromones. Particularly well-studied pheromones of insects, in which these substances perform a variety of functions: for example, sexual pheromones, attracting individuals of the opposite sex; pheromones of aggregation; alarm pheromones emitted at various threats.

Honeybees have two pheromones of anxiety. One of them is secreted by the mandibular glands and is a 2-heptanoneketone. It is believed to be emitted by watchdog bees to activate the colony's protective response when threatened, and furage bees use it to mark flowers that have already been visited. But there are studies that show that this compound performs a different function: with its help bees paralyze parasites such as ticks of the genus Varroa, and remove them from the hive. The second pheromone is secreted by Kozhevnikov's iron at the base of the sting and consists of several compounds. Bees emit this pheromone when the enemy stings or when they are killed, which encourages other individuals to attack.

Secretion of pheromone anxiety in insects is also possible in other dangers, such as infection. But not much is known about such cases. For example, it is known that kissing bedbugs(Triatoma infestans)when infected with the fungus Beauveria bassiana increases the level of propionic acid, which is part of the pheromone of anxiety. Researchers suggest that a large number of this compound causes bedbugs to observe a "social distance" that reduces the transmission of the pathogen. Honeybees in the intestinal parasites of the genus Nosema show various physiological changes, including in the secretion of pheromones in working bees and uteruses. However, noszematose has not yet recorded a change in the level of pheromone anxiety.

A team of biologists from the United States and Turkey led by Christopher Mayack of Sworthmore College studied 100 honeybee workers from 30 hives and found nozematosis in 18 bee families caused by N. ceranae. The scientists then used mass spectrometry to identify the chemical compounds in each hive. It turned out that all contaminated hives had a high content of unsaturated alcohol eikosenol (cis-11-Eikosen-1-ol), one of the main components of the pheromone of anxiety. The effect of this substance depends on the situation. Bees secrete eicosenol as part of the pheromone of anxiety when they are attacked, which stimulates aggression or avoidance. But bees also use this compound to attract other individuals to feeding places.

The authors of the paper believe that elevated eicosenol production at the colony level can lead to a significant change in behavior - and it will be more harmful to the family than the infection itself. Previous studies have shown that healthy bees can kill individuals with nozematosis. But if the hive is completely infected, then individuals with a small degree of infection avoid highly infected. The authors suggest that eicosenol plays a major role in both types of interaction. However, the researchers say that infected bees may be less sensitive to pheromones, so they secrete in greater numbers. Scientists have concluded that further research is needed on the pheromone anxiety of infected bees to determine the exact role of eicosenol.

Nozematosis is a dangerous disease that can cause the bee family to die. However, bees have learned to resist pathogens: scientists have found that the seminal fluid of drones contains substances that negatively affect the life of Nosema apis.

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