How the Carbon Dioxide Affects Bee Physiology, Including Reproduction

While many people are familiar with the image of a beekeeper blowing clouds of carbon dioxide into a hive to calm the insects, little is known about its other effects on bees.

A recent study provided insights into how the chemical compound affects bee physiology, including reproduction.

New clues about how carbon dioxide affects bumble bee reproduction

(Photo : Rentz/Getty Images)

The team of researchers, led by an entomologist from Penn State's College of Agricultural Sciences, set out to figure out how carbon dioxide appears to bypass diapause, a phase similar to hibernation in which bees sleep during the winter, to trigger the reproductive process in bumblebee queens.

Carbon dioxide, the researchers discovered, first caused a change in metabolism, which then caused secondary effects on reproduction, as per ScienceDaily.

The findings, published recently in Insect Biochemistry and Molecular Biology, contradicted previous hypotheses.

Carbon dioxide is commonly used by beekeepers and researchers to sedate bees and other insects, according to the researchers.

In addition to inducing a calming effect, carbon dioxide can also cause a variety of other physiological responses.

While bumblebee queens typically enter diapause during the winter months before establishing a new colony in the spring, bee farmers and researchers may use carbon dioxide to trigger the queens' reproductive process earlier than would occur naturally.

Amsalem stated that she and the other researchers wanted to conduct the study for a variety of reasons.

First, because carbon dioxide is so widely used, she believes it is critical to understand its mode of action in insects, particularly bumblebees, where it is used by commercial apiaries to produce colonies for year-round pollination.

The second goal was to better understand how using carbon dioxide could influence research results.

The researchers conducted two phases of experiments for the study.

The researchers first wanted to gain a better understanding of the physiological effects of carbon dioxide on bumblebee queens.

The bees were divided into two groups by the researchers: those that were not treated and those that were. They were then examined three times: immediately after the treatment, three days later, and ten days later.

The researchers examined the ovaries and measured macronutrient concentrations in several tissues at each time point, which provided information about changes in metabolic function over time.

According to the researchers, this antagonist reduces the levels of juvenile hormone in bumble bees, which regulates reproduction and speeds up metabolism.

Scientists suspected that this hormone is important in the way carbon dioxide affects the physiology of insects.

This time, they discovered that bees with their ovaries removed had a similar change in macronutrients to bees in the control group who still had their ovaries.

According to the researchers, this suggests that carbon dioxide affects metabolism first because bees without reproductive organs experienced the same effect.

Furthermore, bees treated with the juvenile hormone inhibitor did not exhibit these metabolic effects, confirming the role of this hormone in mediating the effects of carbon dioxide, according to the researchers.

According to Amsalem, the findings are critical for understanding not only how carbon dioxide affects bumblebees, but all insects.

CO2 has many different effects on insects, so as scientists, we're looking for a common effect so we can figure out what process or mechanism is causing these effects, she explained.

For example, it promotes reproduction in bees but may inhibit reproduction in other insects. It has an inconsistent effect on reproduction.

However, they believed it is consistent in how it affects metabolism.

Also Read: Global Warming: Plants Absorbing More CO2 Than We Thought

How Rising CO2 Levels May Contribute to Die-Off of Bees

More than a hundred previous studies have found that increased levels of atmospheric carbon dioxide reduce the nutritional value of plants like wheat and rice, as per The Yale School of Environment.

However, the goldenrod study, published last month, was the first to investigate the effects of rising CO2 concentrations on bee diet, and its findings were concerning.

The adverse impact of rising CO2 concentrations on pollen protein levels may be contributing to the global die-off of bee populations by undermining bee nutrition and reproductive success.

"Pollen is becoming junk food for bees," said Lewis Ziska, a plant physiologist at the University of California, Davis.

The United States Department of Agriculture's (USDA) Research Service in Maryland, and the study's lead author.

According to the study, the decline of plant proteins in the face of rising CO2 levels provides an "urgent and compelling case" for CO2 sensitivity in pollen and other plant components.

Because atmospheric carbon dioxide is a building block for plant sugars, increased CO2 levels affect plant physiology by allowing the plant's starchier parts to grow faster and bigger.

This growth dilutes the plant's total protein rather than concentrating it in the grain, resulting in starchier pollen.