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Thermoregulation of foraging honeybees on flowering plants: seasonal variability and influence of radiative heat gain.

Kovac H, Stabentheiner A - Ecol Entomol (2011)

Bottom Line: The thorax temperature excess decreased strongly with increasing T(a) (T(th)-T(a) = 21.6 - 3.6°C).3.An anova revealed that season had the greatest effect on T(th), followed by T(a) and radiation.4.It was presumed the foragers' motivational status to be the main factor responsible for the variation of T(th) between seasons and different plants.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, Karl-Franzens-University of Graz, Universitätsplatz 2 Graz, Austria.

ABSTRACT
1. During nectar and pollen foraging in a temperate climate, honeybees are exposed to a broad range of ambient temperatures, challenging their thermoregulatory ability. The body temperature that the bees exhibit results from endothermic heat production, exogenous heat gain from solar radiation, and heat loss. In addition to profitability of foraging, season was suggested to have a considerable influence on thermoregulation. To assess the relative importance of these factors, the thermoregulatory behaviour of foragers on 33 flowering plants in dependence on season and environmental factors was investigated.2. The bees (Apis mellifera carnica Pollman) were always endothermic. On average, the thorax surface temperature (T(th)) was regulated at a high and rather constant level over a broad range of ambient temperatures (T(th) = 33.7-35.7°C, T(a) = 10-27°C). However, at a certain T(a), T(th) showed a strong variation, depending on the plants from which the bees were foraging. At warmer conditions (T(a) = 27-32°C) the T(th) increased nearly linearly with T(a) to a maximal average level of 42.6 °C. The thorax temperature excess decreased strongly with increasing T(a) (T(th)-T(a) = 21.6 - 3.6°C).3. The bees used the heat gain from solar radiation to elevate the temperature excess of thorax, head, and abdomen. Seasonal dependance was reflected in a 2.7 °C higher mean T(th) in the spring than in the summer. An anova revealed that season had the greatest effect on T(th), followed by T(a) and radiation.4. It was presumed the foragers' motivational status to be the main factor responsible for the variation of T(th) between seasons and different plants.

No MeSH data available.


Related in: MedlinePlus

Thermograms of foraging honeybees on dandelion (Taraxacum officinalis, a) and apricot (Prunus armeniaca, b). (a) Tthorax = 34.6, Thead = 26.0, Tabdomen = 21.7°C, Tblossom = 19.3°C, Ta = 17.3°C, radiation = 66 W m−2. (b) Tthorax = 39.8, Thead = 33.6, Tabdomen = 22.7°C, Tblossom = 21.0°C, Ta = 18.7°C, radiation = 199 W m−2.
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fig01: Thermograms of foraging honeybees on dandelion (Taraxacum officinalis, a) and apricot (Prunus armeniaca, b). (a) Tthorax = 34.6, Thead = 26.0, Tabdomen = 21.7°C, Tblossom = 19.3°C, Ta = 17.3°C, radiation = 66 W m−2. (b) Tthorax = 39.8, Thead = 33.6, Tabdomen = 22.7°C, Tblossom = 21.0°C, Ta = 18.7°C, radiation = 199 W m−2.

Mentions: The temperature of the three bee body parts and of the blossoms' surfaces (in close vicinity to the bees' mouthparts) was calculated from the infrared thermograms (Fig. 1) by means of the AGEMA Research software (FLIR, Stockholm, Sweden) controlled by a self-written Excel VBA-macro (Microsoft Corporation, Santa Rosa, California). The environmental data were automatically extracted from the datalogger files. Values of the body temperature during foraging were taken in regular intervals of about 3–5 s immediately after the insects' landing until their takeoff. This interval was chosen, because bees are able to increase or decrease body temperature within this time and temperature could vary considerably during foraging on one blossom (Fig. 2). The surface temperatures of the head (Thd), thorax (Tth) and abdomen (Tab) were calculated with an infrared emissivity of 0.97, determined for the honeybee cuticle (Stabentheiner & Schmaranzer, 1987; Schmaranzer & Stabentheiner, 1988). Because the ThermaCam works in the long-wave infrared range (7.5–13 µm), the reflected radiation from the bees' cuticle produced only a small measurement error (0.2 °C for 1000 W m−2), which was compensated for. In this way we reached an accuracy of 0.7 °C for the body surface temperature of the bees at a sensitivity of <0.1 °C. The blossom surface temperature was calculated with an infrared emissivity of 0.95, representing a typical value for plants (Lamprecht et al., 2006).


Thermoregulation of foraging honeybees on flowering plants: seasonal variability and influence of radiative heat gain.

Kovac H, Stabentheiner A - Ecol Entomol (2011)

Thermograms of foraging honeybees on dandelion (Taraxacum officinalis, a) and apricot (Prunus armeniaca, b). (a) Tthorax = 34.6, Thead = 26.0, Tabdomen = 21.7°C, Tblossom = 19.3°C, Ta = 17.3°C, radiation = 66 W m−2. (b) Tthorax = 39.8, Thead = 33.6, Tabdomen = 22.7°C, Tblossom = 21.0°C, Ta = 18.7°C, radiation = 199 W m−2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3298660&req=5

fig01: Thermograms of foraging honeybees on dandelion (Taraxacum officinalis, a) and apricot (Prunus armeniaca, b). (a) Tthorax = 34.6, Thead = 26.0, Tabdomen = 21.7°C, Tblossom = 19.3°C, Ta = 17.3°C, radiation = 66 W m−2. (b) Tthorax = 39.8, Thead = 33.6, Tabdomen = 22.7°C, Tblossom = 21.0°C, Ta = 18.7°C, radiation = 199 W m−2.
Mentions: The temperature of the three bee body parts and of the blossoms' surfaces (in close vicinity to the bees' mouthparts) was calculated from the infrared thermograms (Fig. 1) by means of the AGEMA Research software (FLIR, Stockholm, Sweden) controlled by a self-written Excel VBA-macro (Microsoft Corporation, Santa Rosa, California). The environmental data were automatically extracted from the datalogger files. Values of the body temperature during foraging were taken in regular intervals of about 3–5 s immediately after the insects' landing until their takeoff. This interval was chosen, because bees are able to increase or decrease body temperature within this time and temperature could vary considerably during foraging on one blossom (Fig. 2). The surface temperatures of the head (Thd), thorax (Tth) and abdomen (Tab) were calculated with an infrared emissivity of 0.97, determined for the honeybee cuticle (Stabentheiner & Schmaranzer, 1987; Schmaranzer & Stabentheiner, 1988). Because the ThermaCam works in the long-wave infrared range (7.5–13 µm), the reflected radiation from the bees' cuticle produced only a small measurement error (0.2 °C for 1000 W m−2), which was compensated for. In this way we reached an accuracy of 0.7 °C for the body surface temperature of the bees at a sensitivity of <0.1 °C. The blossom surface temperature was calculated with an infrared emissivity of 0.95, representing a typical value for plants (Lamprecht et al., 2006).

Bottom Line: The thorax temperature excess decreased strongly with increasing T(a) (T(th)-T(a) = 21.6 - 3.6°C).3.An anova revealed that season had the greatest effect on T(th), followed by T(a) and radiation.4.It was presumed the foragers' motivational status to be the main factor responsible for the variation of T(th) between seasons and different plants.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, Karl-Franzens-University of Graz, Universitätsplatz 2 Graz, Austria.

ABSTRACT
1. During nectar and pollen foraging in a temperate climate, honeybees are exposed to a broad range of ambient temperatures, challenging their thermoregulatory ability. The body temperature that the bees exhibit results from endothermic heat production, exogenous heat gain from solar radiation, and heat loss. In addition to profitability of foraging, season was suggested to have a considerable influence on thermoregulation. To assess the relative importance of these factors, the thermoregulatory behaviour of foragers on 33 flowering plants in dependence on season and environmental factors was investigated.2. The bees (Apis mellifera carnica Pollman) were always endothermic. On average, the thorax surface temperature (T(th)) was regulated at a high and rather constant level over a broad range of ambient temperatures (T(th) = 33.7-35.7°C, T(a) = 10-27°C). However, at a certain T(a), T(th) showed a strong variation, depending on the plants from which the bees were foraging. At warmer conditions (T(a) = 27-32°C) the T(th) increased nearly linearly with T(a) to a maximal average level of 42.6 °C. The thorax temperature excess decreased strongly with increasing T(a) (T(th)-T(a) = 21.6 - 3.6°C).3. The bees used the heat gain from solar radiation to elevate the temperature excess of thorax, head, and abdomen. Seasonal dependance was reflected in a 2.7 °C higher mean T(th) in the spring than in the summer. An anova revealed that season had the greatest effect on T(th), followed by T(a) and radiation.4. It was presumed the foragers' motivational status to be the main factor responsible for the variation of T(th) between seasons and different plants.

No MeSH data available.


Related in: MedlinePlus