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Honeybee colony thermoregulation--regulatory mechanisms and contribution of individuals in dependence on age, location and thermal stress.

Stabentheiner A, Kovac H, Brodschneider R - PLoS ONE (2010)

Bottom Line: Concerning the active reaction to cold stress by endothermy, age polyethism is reduced to only two physiologically predetermined task divisions, 0 to approximately 2 days and older.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.

View Article: PubMed Central - PubMed

Affiliation: Institut für Zoologie, Karl-Franzens-Universität Graz, Graz, Austria. anton.stabentheiner@uni-graz.at

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 degrees 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 approximately 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 (< approximately 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.

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Thermal relations in open brood nest cells visited by bees.Box plots: median with 1st and 3rd quartile, maximum and minimum. Notches which do not overlap indicate significant differences (P<0.05). nn  =  unmarked workers; red crosses  =  medians of all age groups of marked bees (not significantly different from nn bees, except Tthorax-Tabdomen at Texp = 25 and 30°C, P<0.05, U test).Tcell 30% is the cell wall temperature at the estimated mean contact position of the thorax with the cell wall at 30% cell depth as measured from the base, calculated by linear interpolation between Tcell base and Tcell rim. Numbers  =  measurements (bees).
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pone-0008967-g007: Thermal relations in open brood nest cells visited by bees.Box plots: median with 1st and 3rd quartile, maximum and minimum. Notches which do not overlap indicate significant differences (P<0.05). nn  =  unmarked workers; red crosses  =  medians of all age groups of marked bees (not significantly different from nn bees, except Tthorax-Tabdomen at Texp = 25 and 30°C, P<0.05, U test).Tcell 30% is the cell wall temperature at the estimated mean contact position of the thorax with the cell wall at 30% cell depth as measured from the base, calculated by linear interpolation between Tcell base and Tcell rim. Numbers  =  measurements (bees).

Mentions: Shading of bars  =  thermal stress (Texp). (A) Marked bees on combs; 100% = 12732 bees (measurements) of all age classes. Insert: detailed analysis of 0–2 d old bees. (B) Bees in cells; 100% = 350 bees of all age classes. Percentage of bees in brood nest cells per age class (young to old): 92.5 (184 of 199), 87.5 (70 of 80), 92.3 (36 of 39), 76.2 (16 of 21), 100.0 (5 of 5), 100.0 (6 of 6); no significant differences between age classes (P>0.05, Chi2 = 0.00–6.08). Insert: distribution of unmarked bees on brood and non-brood areas (‘nn’ in Figs 7, 8); n = bees = 100% (per Texp). (A, B) Significant differences between brood and non-brood: * P<0.05, *** P<0.001, Chi2 test.


Honeybee colony thermoregulation--regulatory mechanisms and contribution of individuals in dependence on age, location and thermal stress.

Stabentheiner A, Kovac H, Brodschneider R - PLoS ONE (2010)

Thermal relations in open brood nest cells visited by bees.Box plots: median with 1st and 3rd quartile, maximum and minimum. Notches which do not overlap indicate significant differences (P<0.05). nn  =  unmarked workers; red crosses  =  medians of all age groups of marked bees (not significantly different from nn bees, except Tthorax-Tabdomen at Texp = 25 and 30°C, P<0.05, U test).Tcell 30% is the cell wall temperature at the estimated mean contact position of the thorax with the cell wall at 30% cell depth as measured from the base, calculated by linear interpolation between Tcell base and Tcell rim. Numbers  =  measurements (bees).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2813292&req=5

pone-0008967-g007: Thermal relations in open brood nest cells visited by bees.Box plots: median with 1st and 3rd quartile, maximum and minimum. Notches which do not overlap indicate significant differences (P<0.05). nn  =  unmarked workers; red crosses  =  medians of all age groups of marked bees (not significantly different from nn bees, except Tthorax-Tabdomen at Texp = 25 and 30°C, P<0.05, U test).Tcell 30% is the cell wall temperature at the estimated mean contact position of the thorax with the cell wall at 30% cell depth as measured from the base, calculated by linear interpolation between Tcell base and Tcell rim. Numbers  =  measurements (bees).
Mentions: Shading of bars  =  thermal stress (Texp). (A) Marked bees on combs; 100% = 12732 bees (measurements) of all age classes. Insert: detailed analysis of 0–2 d old bees. (B) Bees in cells; 100% = 350 bees of all age classes. Percentage of bees in brood nest cells per age class (young to old): 92.5 (184 of 199), 87.5 (70 of 80), 92.3 (36 of 39), 76.2 (16 of 21), 100.0 (5 of 5), 100.0 (6 of 6); no significant differences between age classes (P>0.05, Chi2 = 0.00–6.08). Insert: distribution of unmarked bees on brood and non-brood areas (‘nn’ in Figs 7, 8); n = bees = 100% (per Texp). (A, B) Significant differences between brood and non-brood: * P<0.05, *** P<0.001, Chi2 test.

Bottom Line: Concerning the active reaction to cold stress by endothermy, age polyethism is reduced to only two physiologically predetermined task divisions, 0 to approximately 2 days and older.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.

View Article: PubMed Central - PubMed

Affiliation: Institut für Zoologie, Karl-Franzens-Universität Graz, Graz, Austria. anton.stabentheiner@uni-graz.at

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 degrees 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 approximately 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 (< approximately 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.

Show MeSH
Related in: MedlinePlus