Bees Adjust To Seasons with Nutrients In Flowers and 'Dirty Water'

PHYS.org     Tufts University     May 30, 2018

Calcium spikes upward in the diet gathered by bees in preparation for winter. Credit: Steffan Hacker, Tufts University

Researchers at Tufts University have discovered that honey bees alter their diet of nutrients according to the season, particularly as winter approaches. A spike in calcium consumption in the fall, and high intake of potassium, help prepare the bees for colder months when they likely need those minerals to generate warmth through rapid muscle contractions. A careful inventory of the bees' nutrient intake revealed shifting sources (from flowers to mineral rich 'dirty water') and how limitations in nutrient availability from these sources can have implications for the health of both managed and wild colonies.

The study, which is available in the May print edition of the Journal of Insect Physiology, examined mineral content gathered by and contained in adult bees and in their sources of food, exploring how they maintain the right nutritional balance of micronutrients. For most of the minerals tracked, it was found that the bees sought alternate sources to complement variation in the floral supply.

"We typically think of honey bees as gathering all the food they need for the colony from flowers, but in fact, our research showed that bees search strategically among different sources, including water, to boost their stores of calcium and maintain potassium levels in preparation for the cold season," said Philip Starks, associate professor of biology in the School of Arts and Sciences at Tufts. "Honey bee nutritional requirements are quite complex, and they can face limitations because of levels of micronutrients in their environment."

The study findings build on previous research led by Dr. Rachael Bonoan from the Starks lab that revealed that honey bees use water sources to complement, and sometimes supplement, the minerals in their floral diet. For example, as magnesium levels drop in pollen during the summer and fall, the bees pick up the difference from mineral rich water. Alternatively, calcium levels in gathered pollen increase in the fall, but so do the bees' preference for calcium in water, perhaps reflecting a shift from brood rearing to overwintering, the researchers speculate. Ample calcium and potassium are useful for the muscle activity needed to generate heat in the hive during the winter months.

Calcium spikes upward in the diet gathered by bees in preparation for winter. Credit: Steffan Hacker, Tufts UniversityVIEW VIDEO: https://phys.org/news/2018-05-bees-adjust-seas

"These results have implications in the field," said Rachael Bonoan, lead author of the study and recent Ph.D. graduate from the Starks Lab. "Ultimately, one of the goals of studying mineral needs of honey bees is to create season- or crop-specific supplemental diets for beekeepers. Beyond honey bees, we can support wild pollinators by planting diverse floral, and thus nutrient-rich, sources."

There are many factors that have been blamed for the recent decline of bee populations, including the use of pesticides, the emergence of parasites and pathogens, and climate change. While diversity in the food supply may be one factor, its relative impact on the honey bee crisis has not yet been determined. This particular study, however, expands our understanding of the dynamic nutritional needs of bee colonies and provides further insight as to how we might manage the health of honey bee populations that support the natural environment and our food supply.

Also contributing to the study was Tufts University undergraduate Luke O'Connor, whose work formed the basis of his senior honor's thesis.

https://phys.org/news/2018-05-bees-adjust-seasons-nutrients-dirty.html#jCp

Vasculature of the Hives: How Honey Bees Stay Cool

Science Daily    Source: Tufts University    July 23, 2014

Honey bees, especially the young, are highly sensitive to temperature and to protect developing bees, adults work together to maintain temperatures within a narrow range. Recently published research led by Philip T. Starks, a biologist at Tufts University's School of Arts and Sciences, is the first to show that worker bees dissipate excess heat within a hive in process similar to how humans and other mammals cool themselves through their blood vessels and skin.

"This study shows how workers effectively dissipate the heat absorbed via heat-shielding, a mechanism used to thwart localized heat stressors," says Starks. The research is published in the June 10 edition of the journal Naturwissenschaften, which appeared online April 24.

This discovery also supports the theoretical construct of the bee hive as a superorganism -- an entity in which its many members carry out specialized and vital functions to keep the whole functioning as a unit.

Young bees develop within wax cells. For healthy development, the youngsters must be maintained between 32 degrees Celsius, or 89.6 degrees Fahrenheit, and 35 degrees Celsius, or 95 degrees Fahrenheit. In contrast, adults can withstand temperatures as high as 50 degrees Celsius, or 122 degrees Fahrenheit

Previous research has shown that workers bees, among other duties, control the thermostat essential to the hive's survival.

When temperatures dip, worker bees create heat by contracting their thoracic muscles, similar to shivering in mammals. To protect the vulnerable brood when it's hot, workers fan the comb, spread fluid to induce evaporative cooling, or -- when the heat stress is localized -- absorb heat by pressing themselves against the brood nest wall (a behavior known as heat-shielding).

But until the Tufts study, scientists did not know how the bees got rid of the heat after they had absorbed it.

Starks' team included doctoral student Rachael E. Bonoan, former undergraduate student Rhyan R. Goldman, and Peter Y. Wong, a research associate professor in the department of mechanical engineering in the School of Engineering at Tufts. Bonoan and Goldman collected data on seven active honeybee hives that were framed by clear Plexiglas walls.

Each colony numbered 1,000 to 2,500 adult bees. An eighth hive, empty of bees, was used as a control. Using a theater light, the researchers raised the internal temperature of all eight hives for 15 minutes. Temperature probes recorded internal temperature throughout the heating portion of the experiment.

As anticipated, the worker bees pressed their bodies against the heated surfaces near the brood. Like insect sponges, they absorbed the heat, which lowered temperatures. After 15 minutes, a time brief enough to prevent serious harm to the bees, the theater light was turned off.

Immediately following, heat movement within the hive and external hive temperatures were tracked via thermal imaging. Within 10 minutes of cooling, temperatures in the active hives were down to safe levels. Meanwhile, the control hive remained at 40 degrees Celsius. "Since the control hive did not have bees, the differences in temperature were likely caused by worker behavior," Starks says.

Using thermal imaging, the scientists observed that temperatures increased peripheral to the heated regions of the hive as the brood nest began to cool. The thermal images clearly showed that the bees had physically moved the absorbed heat in their bodies to previously cooler areas of the hive. "Moving heat from hot to cool areas is reminiscent of the bioheat transfer via the cardiovascular system of mammals," says Starks.

This research was supported by the Tufts University Biology Department and the Tufts University National Science Foundation Research Experience for Undergraduates Program (DBI 263030).

Read at: http://www.sciencedaily.com/releases/2014/07/140723161912.htm