Honeybee Colony Thermoregulation – Regulatory Mechanisms and Contribution of Individuals in Dependence on Age, Location and Thermal Stress

Abstract

Honeybee larvae and pupae are extremely stenothermic, i.e. they strongly depend on accurate regulation of brood nest temperature for proper development (33–36°C). Here we study the mechanisms of social thermoregulation of honeybee colonies under changing environmental temperatures concerning the contribution of individuals to colony temperature homeostasis. Beside migration activity within the nest, the main active process is “endothermy on demand” of adults. An increase of cold stress (cooling of the colony) increases the intensity of heat production with thoracic flight muscles and the number of endothermic individuals, especially in the brood nest. As endothermy means hard work for bees, this eases much burden of nestmates which can stay ectothermic. Concerning the active reaction to cold stress by endothermy, age polyethism is reduced to only two physiologically predetermined task divisions, 0 to ∼2 days and older. Endothermic heat production is the job of bees older than about two days. They are all similarly engaged in active heat production both in intensity and frequency. Their active heat production has an important reinforcement effect on passive heat production of the many ectothermic bees and of the brood. Ectothermy is most frequent in young bees (<∼2 days) both outside and inside of brood nest cells. We suggest young bees visit warm brood nest cells not only to clean them but also to speed up flight muscle development for proper endothermy and foraging later in their life. Young bees inside brood nest cells mostly receive heat from the surrounding cell wall during cold stress, whereas older bees predominantly transfer heat from the thorax to the cell wall. Endothermic bees regulate brood comb temperature more accurately than local air temperature. They apply the heat as close to the brood as possible: workers heating cells from within have a higher probability of endothermy than those on the comb surface. The findings show that thermal homeostasis of honeybee colonies is achieved by a combination of active and passive processes. The differential individual endothermic and behavioral reactions sum up to an integrated action of the honeybee colony as a superorganism.

Honeybees and nectar nicotine: Deterrence and reduced survival versus potential health benefits

“…Caged honeybees consumed the stored nectar after a few days, which coincided with increased activity (A. Köhler, pers. observation) and the development of endothermic ability (Stabentheiner et al, 2010). The evaporation of nectar in the cells led to a more concentrated sugar solution, which might have resulted in workers preferring it over the more dilute nectar provided ad libitum in the feeder.…”

Weight of evidence evaluation of a network of adverse outcome pathways linking activation of the nicotinic acetylcholine receptor in honey bees to colony death

“…Chill coma results in death of the bee if low temperature is experienced for an extended duration. Additionally, honey bee larvae and pupae are stenothermic, meaning they depend on strict temperature regulation for proper development (Stabentheiner et al, 2010). Deviations from the optimal hive temperature range can lead to crippling or death of the developing bee (Fyg, 1959).…”

Organisms as Persisters

“…When the temperature in the hive drops below the optimum, worker bees group around the brood nest and vibrate their wings producing heat from their thoracic muscles to bring the temperature back to its optimum (Seeley 1985;Stabentheiner, Kovac, and Brodschneider 2010). They also cool the hive when it exceeds the optimum temperature, by spreading out, fanning, evaporating water, or as a last resort evacuating the hive.…”