Diverse Food Sources Keep Honeybees Healthy

Honey bee (Apis mellifera) collecting pollen

Biological Strategy

Honeybees

Anika Hazra

Image: Luc Viatour / Wikimedia Commons / CC BY SA - Creative Commons Attribution + ShareAlike

Protect From Microbes

In living systems, microbes play important roles, such as breaking down organic matter and maintaining personal and system health. But they also pose threats. Bacteria can be pathogens that cause diseases. Some bacteria create colonies called biofilms that can coat surfaces, reducing their effectiveness–for example, inhibiting a leaf’s ability to photosynthesize. Living systems must have strategies for protecting from microbes that cause disease or become so numerous that they create an imbalance in the system. At the same time, living systems must continue living in harmony with other microbes. Some living systems kill microbes. Others repel without killing to reduce the chances that microbes will adapt to the lethal strategy and become resistant to it. For example, some pea seedlings exude a chemical that inhibits biofilm buildup.

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Regulate Cellular Processes

Cells are the basic building blocks of all living systems, so cellular processes dictate how physiological processes occur within those systems. Cells (whether entire unicellular organisms or parts of multicellular living systems) grow, metabolize nutrients (that is, chemically transform them), produce proteins and enzymes, replicate, and move. Cells as part of multicellular systems rarely act alone, instead having ways to signal to start and complete simple to quite complex interactions. How skin heals is a good example of the role of cellular processes. Blood cells called platelets release clotting factors to stop the bleeding; white blood cells rid the area of foreign materials and release molecules to coordinate healing; cells called fibroblasts start rebuilding using proteins called collagen; new blood vessels form; and skin cells called keratinocytes create the new surface.

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Distribute Solids

Solids include resources such as food, seeds, spores, and leaves, which living systems must sometimes move to accomplish various activities such as pollinating, feeding their young, or building shelters. To effectively distribute solids, living systems must use strategies appropriate to the sizes and types of solids and the media in which they exist (air, water, or another medium). This may entail strategies beyond simply holding and carrying solids. For example, some seeds are carried by the wind to new locations for germination. Others–like the burdock plant’s hooked seeds–cling to animal fur to be transported.

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Store Solids

Living systems, especially organisms, must sometimes store solids, often pieces of material (such as mud, seeds, stones, or leaf fragments). They use these solids for building structures, feeding during periods of low food availability, or other purposes. To be effective, the storage strategy must be appropriate to the sizes of solids and to the media in which they exist, whether air, water, or other solids like soil. It must also safely arrange the solids for storage in a location appropriate to either short- or long-term storage. An example is the Clark’s nutcracker, a forest bird that can collect up to 150 pine seeds and temporarily hold them in an expandable pouch under its head, where it doesn’t interfere with the bird’s daily activities.

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Capture, Absorb, or Filter Solids

Some living systems must secure solid particles such as sediment, usually to keep the particles from hindering their health or activity. The most common way in which they do this is through filtering. To be effective, a filtering system must be appropriate to the sizes of solid particles to be captured and must capture only what is needed. It must also be effective in the appropriate media–air, water, or sometimes solids like soil. An example is mangroves, which are trees that grow along ocean coasts. Their root system slows down and settles sediment out of the water, building up soil to support the mangrove ecosystem.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Honeybee immune systems depend more on protein diversity than quantity.

Introduction

A well-rounded diet is required to get the nutrients our bodies need to function—this is true as true for humans as it is for any other living thing. In this case, let’s take a closer look at the diet of the honeybee (Apis mellifera). Experiments and observations have revealed how carefully the honeybee’s immune system is maintained through diet: a lack of diverse sources reduces the ability of its immune system to function and increases the honeybee’s susceptibility to disease.

The Strategy

Immune system maintenance requires a lot of energy and resources, including a consistent supply of protein from pollen. A single source of protein is not enough to fulfill the honeybee’s dietary needs, so a habitat that offers pollen sources from a variety of plants is ideal. A honeybee colony overridden by disease likely does not have access to the food resources it needs to sustain immune function, which can indicate that the bees live in a degraded ecosystem.

The impact of a diverse diet on the honeybee’s immunity can be measured through its blood cell concentration, fat body content, phenoloxidase activity and oxidase (GOX) activity.

The first three measures relate to the immune function of individuals. Blood cell concentration and phenoloxidase activity measure a bee’s ability to identify, trap, and remove parasites. Fat bodies are where antimicrobial s are made.

The fourth measure relates to the colony as a whole. GOX allows a colony to be sterilized through the production of hydrogen peroxide, which has antiseptic properties. These antiseptic products are secreted into honey and other larval food.

Experimentally, it has been shown that increasing the amount of protein in a honeybee’s diet did not significantly improve its immunity, but increasing the diversity of the honeybee’s diet did.

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Honey bee (Apis mellifera) with pollen basket on hind leg

Image: Ivar Leidus / Wikimedia Commons / CC BY SA - Creative Commons Attribution + ShareAlike

Honey bee (Apis mellifera) on a white sweet clover (Melilotus albus) with collected pollen attached to its hind leg

The Potential

The decline of honey bees has been attributed to many different causes, including susceptibility to disease due to weakened immune systems. The understanding that the diversity of food sources is important for individual and colony immunity can lead to new treatments and management styles to improve the health of honeybees everywhere.

In addition, the specific chemistry of honeybee health could inspire new therapies for bees, other invertebrates, and other animals as well.

Finally, a closer examination of the interplay between individual and colony immune functions could lead to insights for better management of the health of other communities, including human ones.

Last Updated January 1, 2022

References

“Protein feeding modified both individual and social IC [immunocompetence] but increases in dietary protein quantity did not enhance IC. However, diet diversity increased IC levels. In particular, polyfloral diets induced higher GOX [glucose oxidase] activity compared with monofloral diets, including protein-richer diets. These results suggest a link between protein nutrition and immunity in honeybees and underscore the critical role of resource availability on pollinator health.” (Alaux et al. 2010:562)

“As social organisms, honeybees depend not only on individual immunity, but also on the overall functioning of the hive. So, we also analysed glucose oxidase (GOX) activity as a parameter of social immunity. Mainly expressed in the HPGs (Ohashi et al. 1999), GOX catalyses the oxidation of b-D-glucose to gluconic acid and hydrogen peroxide, the latter having antiseptic properties. The antiseptic products are secreted into larval food and honey, which contributes to colony-food sterilization (White et al. 1963), and hence, to the prevention of disease contamination at the group level.” (Alaux et al. 2010:562)

Journal article

Diet effects on honeybee immunocompetence

Biology Letters | 2010 | Cédric Alaux, François Ducloz, Didier Crauser & Yves Le Conte

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