Muscles Create Heat to Warm Nest

photograph of yellow and black honey bees in their golden yellow hive

Biological Strategy

Western honeybee

Hannah Schulze

Image: Pierre GRAND / Flickr / Public Domain - No restrictions

Sense Temperature Cues From the Environment

Some living systems use their ability to perceive temperature to find prey or avoid predators, or as a way to gain information about their environment, such as whether they are near a warm or cold place. Temperature gradients can be subtle and modulate as they travel through water, air, or solids. Living organisms must therefore have a variety of thermal sensors appropriate to a given medium (liquid, gas, solid). Some even have a way to “visualize” a signal’s source. For example, the rattlesnake has heat sensors with thousands of nerve endings located in pit-shaped holes on each side of its face. The sensitivity of the pits overlaps, giving the snake a bifocal image of the heat’s source.

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Transform Thermal Energy

Heat is necessary for survival, but too much of it can be damaging to an organism. Explore the ways different living things have adapted to use or transform different types of thermal energy.

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Protect From Temperature

Many living systems function best within specific temperature ranges. Temperatures higher or lower than that range can negatively impact a living system’s physiological or chemical processes, and damage its exterior or interior. Living systems must manage high or low temperatures using minimal energy, which often requires controlling responses along incremental temperature changes. To do so, living systems use a variety of strategies, such as avoiding high or low temperatures, removing excess heat, and holding heat in. Insulation is a well-known example of managing low temperatures by retaining heat using thick layers of hair, fur, or feathers to hold warm air next to the skin.

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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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Flight muscles of the western honey bee warm the brood nest by contracting without wing movement and transferring heat to brood cells.

Honeybee colonies keep the brood nest temperature between 33 and 36 degrees Celsius using muscle movement to warm the hive. Bees, like many insects, are cold blooded and require their brood to remain within a small temperature range to continue normal development. Responding to temperature changes in the environment, or thermoregulation of the nest, is the job of special heater bees. If a heater bee is trying to warm an individual brood cell, it can press against the top of the cell with its thorax, or midsection, to transfer heat to the developing young inside. Similarly, bees can also crawl inside a neighboring cell to transfer heat. The current leading hypothesis says heating is accomplished using muscle contraction for periods of time up to 45 minutes. The muscles that contract are flight muscles, and decoupling the wings from these muscles separates wing movement from muscle activity that would normally initiate flight; that way, the muscles can contract without moving the wings. The heat produced from muscle contraction warms the bee’s body up to 44 degrees Celsius, about 10 degrees warmer than a normal bee. Body heat transferred to the brood cells can effectively circulate around the hive and maintain a stable temperature in the hive overall.

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Last Updated April 24, 2018

References

“We find that many bees that are apparently resting inside empty cells in the brood comb are participating in the regulation of brood temperature by serving as a heat source for the neighbouring, sealed, brood cells. This hitherto unrecognised thermal activity of bees inside cells is remarkable because long-duration cell visitors were previously considered to be resting and also because heat production inside cells provides a way to transfer heat to the brood more efficiently than heating via the brood caps.” (Kleinhenz et al. 2003:4218).

Journal article

Hot bees in empty broodnest cells: heating from within

Journal of Experimental Biology | 01/12/2003 | Kleinhenz M, Bujok B, Fuchs S, Tautz J

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Reference

“Bees use two pairs of big fibrillar muscles, the dorsal longitudinal (DL) and the dorsoventral (DV) indirect flight muscles in various behaviours. The most important behaviours include warming of individuals in preparation for flight (Esch, 1960; Heinrich, 1980), flight itself (Esch etal. 1975; Esch 1976), communal hive heating (Himmer, 1932; Esch, 1960; Heinrich, 1987) and fanning during regulation of hive temperatures (Lindauer, 1954).” (Esch and Goller 1991:419).

“The big indirect flight muscles in the thorax of honeybees and bumblebees show two modes of action: they contract with ‘conventional’ twitches in response to slowly repeated muscle potentials and go into tetanus at higher muscle potential frequencies. They can also contract much faster when quickly stretched (stretch activation)” (Esch and Goller 1991:419).

Journal article

Neural Control of Fibrillar Muscles in Bees During Shivering and Flight

Journal of Experimental Biology | 28/05/1991 | Harold Esch, Franz Goller

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