The fungicide Pristine® inhibits mitochondrial function in vitro but not flight metabolic rates in honey bees

Honey bees and other pollinators are exposed to fungicides that act by inhibiting fungal mitochondria. Here we test whether a common fungicide (Pristine®) inhibits the function of mitochondria of honeybees, and whether consumption of ecologically-realistic concentrations can cause negative effects on the mitochondria of flight muscles, or the capability for flight, as judged by CO₂ emission rates and thorax temperatures during flight. Direct exposure of mitochondria to Pristine® levels above 5 ppm strongly inhibited mitochondrial oxidation rates in vitro. However, bees that consumed pollen containing Pristine® at ecologically-realistic concentrations (≈1 ppm) had normal flight CO₂ emission rates and thorax temperatures. Mitochondria isolated from the flight muscles of the Pristine®-consuming bees had higher state 3 oxygen consumption rates than control bees, suggesting that possibly Pristine®-consumption caused compensatory changes in mitochondria. It is likely that the lack of a strong functional effect of Pristine®-consumption on flight performance and the in vitro function of flight muscle mitochondria results from maintenance of Pristine® levels in the flight muscles at much lower levels than occur in the food, probably due to metabolism and detoxification. As Pristine® has been shown to negatively affect feeding rates and protein digestion of honey bees, it is plausible that Pristine® consumption negatively affects gut wall function (where mitochondria may be exposed to higher concentrations of Pristine®).     

The control of the proventriculus in the honeybee (Apis mellifera carnica L.) I. A dynamic process influenced by food quality and quantity?

The control of crop emptying in foraging honeybees was investigated in individuals trained to collect defined amounts of sugar solutions. Following feeding, they were dissected after fixed periods of time in order to measure crop content and haemolymph sugar titers. Between feeding and dissection, the metabolic rate of every investigated forager was measured using open-flow respirometry, so as to assess the effects of both food quality (concentration, molarity and viscosity of the fed sugar solution) and food quantity on the transport rate through the proventriculus. The sugar transport rate through the proventriculus was observed to be mainly dependent on the metabolic expenditure of the individual. Bee foragers were able to precisely adjust the sugar transport rate to their metabolic rates, but under certain conditions, an excess of sugars was transported through the proventriculus, more than needed to cover the bee’s energetic demands. This excess depended on the nutritive value and quantity of the fed sugar solution, and on the time after feeding. It did not depend on the metabolic rate of the bee, the molarity, or the viscosity of the fed sugar solution. As long as the bees did not exhaust their crop contents, the haemolymph sugar titers were unaffected by this excess amount transported, by the time after feeding, the concentration and the viscosity of the fed sugar solution. For all feeding conditions assayed, the haemolymph trehalose titer remained constant, while the titers of other haemolymph sugars varied. It is suggested that the trehalose concentration in the haemolymph is regulated in honeybees, and that it represents the controlled variable in the feedback loop responsible for the transport rate through the proventriculus.     

Flight substrates and their regulation by a member of the AKH/RPCH family of neuropeptides in Cerambycidae

The pattern of metabolic changes during tethered flight with lift-generation was investigated in two South African species of long-horned beetles (family: Cerambycidae), namely Phryneta spinator and Ceroplesis thunbergi. Energy substrates were measured in haemolymph and flight muscles at rest, after a flight period of 1 min at an ambient temperature of 25-29 degrees C, and 1 h thereafter. Flight diminished the levels of proline and carbohydrates in the haemolymph and proline and glycogen in the flight muscles of both species, and caused an increase in the levels of alanine in both compartments. The concentration of lipids in the haemolymph, however, was not changed upon flight in either species. The resting period of 1 h following a 1 min flight episode, was sufficient to reverse the metabolic situation in haemolymph and flight muscles to pre-flight levels in both species. Purification of an extract of the corpora cardiaca from the two beetle species on RP-HPLC, resulted in the isolation and subsequently in the identification (by mass spectrometry, Edman degradation and RP-HPLC) of an octapeptide of the AKH/RPCH family, denoted Pea-CAH-I (pGlu-Val-Asn-Phe-Ser-Pro-Asn-Trpamide), present in each species. It was demonstrated that low doses of Pea-CAH-I elicited increases in the concentration of proline, as well as carbohydrates, in the haemolymph of both species. The levels of lipids, however, remained unchanged upon injection of this peptide. It is concluded that, upon stimulation by flight, the peptide Pea-CAH-I is released from the corpus cardiacum of a cerambycid beetle and is responsible for the regulation of the major flight substrates, proline and carbohydrates, of these beetles.     

The control of the proventriculus in the honeybee (Apis mellifera carnica L.) II. Feedback mechanisms

The mechanisms underlying the control of solution transport rates through the proventriculus in foraging honeybees were investigated in individuals trained to collect defined amounts of sugar solutions. Following feeding, bees were injected either with metabolisable (glucose, fructose, trehalose), or non-metabolisable (sorbose) sugars, in order to distinguish between haemolymph osmolarity and haemolymph sugar levels as factors controlling the solution transport rates through the proventriculus. After a fixed period, workers were dissected in order to measure crop content and haemolymph sugar titers. Between feeding and dissection, the metabolic rate of every investigated forager was measured using open-flow respirometry. Bees injected with metabolisable sugars 15 min after feeding were observed to reduce their solution transport rates through the proventriculus, but injection of non-metabolisable sugars had no influence on them. This suggests that the solution transport rate through the proventriculus is controlled by the concentration of metabolisable compounds in the haemolymph, and not by the haemolymph osmolarity. A period of 10 min after injection of metabolisable sugars was enough to observe reduced solution transport rates. However, if bees were injected only 5 min after feeding, no reduced solution transport rates were observed 10 min after injection.     

Evidence for mutualism between a flower-piercing carpenter bee and ocotillo: use of pollen and nectar by nesting bees

Abstract.

• 1 Carpenter bees (Xylocopa californica arizonensis) in west Texas, U.S.A., gather pollen and ‘rob’ nectar from flowers of ocotillo (Fouquieria splendens). When common, carpenter bees are an effective pollen vector for ocotillo. We examined ocotillo's importance as a food source for carpenter bees.
• 2 The visitation rate of carpenter bees to ocotillo flowers in 1988 averaged 0.51 visits/flower/h and was 4 times greater than that of queen bumble bees (Bombus pennsylvanicus sonorus), the next most common visitor. Nectar was harvested thoroughly and pollen was removed from the majority of flowers. Hummingbird visits were rare.
• 3 Pollen grains from larval food provisions were identified from sixteen carpenter bee nests. On average, 53% of pollen grains sampled were ocotillo, 39% were mesquite (Prosopis glandulosa), and 8% were Zygophyllaceae (Larrea tridentata or Guaiacum angustifolium). Carpenter bee brood size averaged 5.8 per nest.
• 4 We measured the number of flowers, and production of pollen and nectar per flower by mature ocotillo plants, as well as the quantity of pollen and sugar in larval provisions. An average plant produced enough pollen and nectar sugar to support the growth of eight to thirteen bee larvae. Ocotillo thus has the potential to contribute significantly to population growth of one of its key pollinators.
• 5 Although this carpenter bee species, like others, is a nectar parasite of many plant species, it appears to be engaged in a strong mutualism with a plant that serves as both a pollen and as a nectar source during carpenter bee breeding periods.

     

Pyrgomorphid grasshoppers of the genus Phymateus contain species-specific decapeptides of the AKH/RPCH family regulating lipid-mobilization during flight

Abstract. Using heterologous and conspecific bioassays, two peptides have been isolated from methanolic extracts of corpora cardiaca from the pyrgomorphid grasshopper Phymateus morbillosus L.The structures of both peptides were elucidated by a combination of Edman degradation, after deblocking the N-terminal pyroglutamic acid residue, and mass spectrometric techniques.One peptide is an octapeptide (pGlu-Leu-Asn-Phe-Ser-Thr-Gly-TrpNH₂) which also occurs in other insects and is code-named Scg-AKH-II.The second peptide is a novel decapeptide member of the AKH/RPCH family (pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-SerNH₂ code-named here Phm-AKH.It is the first example of a different peptide in the same genus.The analysis of changes of metabolites in the haemolymph, fat body and flight muscles of male P.morbillosus during a 30 min flight and rest after flight reveal an overall picture of flight metabolism similar to that of Locusta migratoria. Carbohydrate-fuelled metabolism is pronounced during the first 15 min of flight, whereas lipid-based metabolism is mainly used thereafter.By analogy with work on L.migratoria , it is concluded that the endogenous peptides of P.morbillosus regulate these metabolic events.     

Importance of proline and other amino acids during honeybee flight

Summary. The levels of proline and other amino acids in the haemolymph and other body parts of honeybee foragers were investigated by HPLC analysis. The concentrations of proline in the blood of glucose-fed or -injected bees finishing their exhaustive tethered flights on a roundabout were significantly reduced compared to bees that were fed and rested for one hour. This indicates some utilization of proline during flight metabolism. The levels of essential amino acids and of the sum of all amino acids except proline remained roughly constant, indicating that the decrease of proline did not result from a changed haemolymph volume. ¹⁴C-labelled proline was injected into bees either shortly before starting their flight or before a resting period of equal duration in an incubator at the same temperature. Bees that rested had incorporated more proline into thorax body protein, and less of the labelled substance was unrecovered ("missing") and considered to be respired or less probably defecated. If the entire amount of missing ¹⁴C-proline is regarded as exhaled, the oxidative breakdown of proline reached higher levels after flight than in rested bees. This is another hint that proline is utilized during flight. Usually the exhaled amount did not exceed 10 μg proline in half an hour of flight. Although our data indicate involvement of proline in flight metabolism, the amount metabolized is low compared to the utilization of carbohydrates. Received December 5, 1998, Accepted February 1, 1999     

Physiological and biochemical aspects of flight metabolism in cocoon-enclosed adults of the fruit beetle,Pachnoda sinuata

We studied several aspects of flight metabolism in cocoon-enclosed adults of the fruit beetle Pachnoda to investigate their flight capability. The majority of adults which were forcefully removed from their pupal cocoon flew off within 5 min of exposure to bright sunlight. Most of the beetles which did not fly voluntarily were, however, capable of flight. Compared with 2-4 week old adults of the same species, cocoon-enclosed adults have higher reserves of glycogen in flight muscles and fat body, whereas the level of total carbohydrates in the haemolymph and the concentration of proline in haemolymph, flight muscles and fat body were similar.Enzymes involved in carbohydrate breakdown (MDH, GAPDH) were more active in flight muscles and fat body of cocoon-enclosed adults compared with adults, while enzymes of proline metabolism in the flight muscles (AlaT, NAD-ME) and fat body (AlaT, NADP-ME) had similar activities in cocoon-enclosed adults and adults. An enzyme of the beta-oxidation of fatty acids (HOAD) had similar activities in flight muscles and fat body of cocoon-enclosed adults and adults.Mitochondria isolated from flight muscles of adults removed prematurely from their cocoon favour the oxidation of proline and pyruvate. Pyruvate, however, is oxidized at higher rates than by mitochondria isolated from flight muscles of adults.During a short lift-generating flight, cocoon-enclosed adults proved that their flight muscles are capable of strong flight performance. During these flights, cocoon-enclosed adults consume proline and carbohydrates at a similar rate to that of adults.The endogenous AKH peptide, Mem-CC, has hyperprolinaemic and hypertrehalosaemic activity in cocoon-enclosed adults. The hypertrehalosaemic effect, however, is stronger in cocoon-enclosed adults than in adults.The content of Mem-CC in corpora cardiaca of larvae (3rd instar), cocoon-enclosed adults and 1 day-old adults is similar at 5-6 pmol per pair of corpora cardiaca, whereas it is higher in 10 day-old adults and 20 day-old adults (37 and 15 pmol per pair corpora cardiaca, respectively).From these results we conclude that cocoon-enclosed adults comply with all the prerequisites for flight performance before they leave their pupal cocoon. Furthermore, cocoon-enclosed adults have a more pronounced carbohydrate-based metabolism before they leave their cocoon compared with adults, which suggests that carbohydrate breakdown is mainly involved in such activities as leaving the cocoon and burrowing activity thereafter.     

Flight fuel and neuropeptidergic control of fuel mobilisation in the twig wilter, Holopterna alata (Hemiptera, Coreidae)

The corpus cardiacum of the twig wilter Holopterna alata contains a factor that elicits increases in the concentration of lipids in the haemolymph of twig wilters and migratory locusts and causes hypertrehalosaemia in American cockroaches. A hyperlipaemic neuropeptide was isolated from corpora cardiaca of H. alata in a single high-performance liquid chromatography step. The primary sequence of this peptide was assigned by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, biological assay and co-elution with the synthetic peptide. The adipokinetic peptide of H. alata is an octapeptide with the sequence pGlu-Leu-Asn-Phe-Ser-Thr-Gly-Trp amide denoted Schgr-AKH-II which was sequenced previously from the corpora cardiaca of a number of Caelifera, Ensifera and some Hymenoptera. A dose of 1pmol of synthetic Schgr-AKH-II causes a pronounced hyperlipaemic effect in the twig wilter. Physiological experiments with the twig wilter reveal that during flight periods of 3 min, the normally low carbohydrate concentration in the haemolymph is significantly diminished, whereas the lipid concentration stays constant in most cases. During a subsequent rest period of 60 min after a 3 min flight episode, however, the concentration of lipids in the haemolymph increases substantially and significantly, indicating that lipids, too, are a major fuel during flight of twig wilters. This is corroborated by the activation of the enzyme triacylglycerol (TAG) lipase in the fat body, but not in the flight muscles, by injection of 5 pmol of synthetic Schgr-AKH-II, the endogenous adipokinetic hormone that is thought to be released during flight. Moreover, in the thorax there is a significant decrease in the concentration of glycogen and lipids measured after flight plus 60 min of rest compared to non-flown twig wilters, whereas no significant changes were monitored for these substrates stored in the abdomen. When the change in lipid class composition was analysed during flight plus 60 min of rest, TAG which comprised the major class in all compartments analysed (thorax, abdomen, haemolymph) was significantly reduced in abdomen and thorax, and diacylglycerol was significantly increased in all three compartments. From all the data collected, it is concluded that lipids are the major fuel class for flight in H. alata and that the contribution of carbohydrates is minimal.     

Carpenter Bee (Xylocopa micans) Risk Indifference and a Review of Nectarivore Risk-sensitivity Studies

This paper presents new results of risk-sensitive foraging studiesof the carpenter bee, Xylocopa micans, and reviews the workto date on risk sensitivity in nectarivores. In the field, nectarivoreschoose among alternative food sources (flowers) that differin the variabilities of their nectar rewards. In the lab, theforaging situation for carpenter bees was experimentally simplifiedby offering the bees a choice between either "low variance"or "high variance" artificial flowers. The two flower typesdiffered in their variabilities but offered the same expectedshortterm rates of net energy gain to test the predictions ofthe short-term rate maximization mechanism. Foragers were testedunder two energy budget conditions, hungry and well-fed, totest the predictions of the z-score model. Individual carpenterbees were indifferent to variability in both nectar volume andnectar sugar concentrations, and their risk-indifference wasunaffected by energy budget. These findings of risk indifferencesupport neither the variance discounting nor the z-score modelof risk sensitivity. Since the low and high variance flowertypes are equivalent for carpenter bees in short-term rate ofenergy gain, there can be no selection on carpenter bees tobe sensitive to variability based on differences in rate ofgain. Studies of risk sensitivity in honey bees and bumble beesusing variance in nectar concentration support this contention.These findings are compared with other nectarivore risk sensitivitystudies in order to highlight the most likely mechanisms underlyingaversion to variation in nectar rewards (short-term rate maximizing,the Weber-Fechner law of perception and learning non-empty flowers)and to suggest future research in the interplay of these threemechanisms.     

Diacylglycerol-transporting lipoproteins and flight in Locusta

Evidence from chromatographic and heparin precipitation studies shows that the ‘heparin-soluble’ lipoprotein, A⁺, forms in the haemolymph during flight. In locusts flown continuously for 60 min, lipoprotein A⁺ occurs in the haemolymph at low concentrations but accumulates during a short rest period following flight. After injections of tissue extracts containing adipokinetic hormone (AKH), A⁺ accumulates in the haemolymph but disappears more rapidly in flying locusts than in resting locusts. This difference in the rate of disappearance of diacylglycerol from the lipoprotein A⁺ can be used to estimate its rate of utilization during sustained flight (approx. 100μg. min^?1 from 45–90 min of flight). It is suggested that lipoprotein A⁺ is the major carrier of diacylglycerol from the fat body to the flight muscles during prolonged flight. The steady state concentrations of total diacylglycerol and ‘heparin-soluble’ diacylglycerol during continuous flight are unaffected when tissue extracts containing AKH are injected before flight. This suggests that there is a close homeostatic control over the steady state concentration of haemolymph lipid during flight.     

Unique features of flight muscles mitochondria of honey bees (Apis mellifera L.)

Honey bees Apis mellifera L. are one of the most studied insect species due to their economic importance. The interest in studying honey bees chiefly stems from the recent rapid decrease in their world population, which has become a problem of food security. Nevertheless, there are no systemic studies on the properties of the mitochondria of honey bee flight muscles. We conducted a research of the mitochondria of the flight muscles of A. mellifera L. The influence of various organic substrates on mitochondrial respiration in the presence or absence of adenosine diphosphate (ADP) was investigated. We demonstrated that pyruvate is the optimal substrate for the coupled respiration. A combination of pyruvate and glutamate is required for the maximal respiration rate. We also show that succinate oxidation does not support the oxidative phosphorylation and the generation of membrane potential. We also studied the production of reactive oxygen species by isolated mitochondria. The greatest production of H₂O₂ (as a percentage of the rate of oxygen consumed) in the absence of ADP was observed during the respiration supported by α‐glycerophosphate, malate, and a combination of malate with another NAD‐linked substrate. We showed that honey bee flight muscle mitochondria are unable to uptake Ca²⁺‐ions. We also show that bee mitochondria are able to oxidize the respiration substrates effectively at the temperature of 50°С compared to Bombus terrestris mitochondria, which were more adapted to lower temperatures.     

Nectar robbery by bees Xylocopa virginica and Apis mellifera contributes to the pollination of rabbiteye blueberry

Honey bees, Apis mellifera L., probe for nectar from robbery slits previously made by male carpenter bees, Xylocopa virginica (L.), at the flowers of rabbiteye blueberry, Vaccinium ashei Reade. This relationship between primary nectar robbers (carpenter bees) and secondary nectar thieves (honey bees) is poorly understood but seemingly unfavorable for V. ashei pollination. We designed two studies to measure the impact of nectar robbers on V. ashei pollination. First, counting the amount of pollen on stigmas (stigmatic pollen loading) showed that nectar robbers delivered fewer blueberry tetrads per stigma after single floral visits than did our benchmark pollinator, the southeastern blueberry bee, Habropoda laboriosa (F.), a recognized effective pollinator of blueberries. Increasing numbers of floral visits by carpenter bee and honey bee robbers yielded larger stigmatic loads. As few as three robbery visits were equivalent to one legitimate visit by a pollen-collecting H. laboriosa female. More than three robbery visits per flower slightly depressed stigmatic pollen loads. In our second study, a survey of 10 commercial blueberry farms demonstrated that corolla slitting by carpenter bees (i.e., robbery) has no appreciable affect on overall V. ashei fruit set. Our observations demonstrate male carpenter bees are benign or even potentially beneficial floral visitors of V ashei. Their robbery of blueberry flowers in the southeast may attract more honey bee pollinators to the crop.     

Osmoregulation in a nectar-feeding insect, the carpenter bee Xylocopa capitata: water excess and ion conservation

Abstract The liquid diet and high metabolic water production during flight in the carpenter bee Xylocopa capitata Smith 1854 (Hymenoptera, Anthophoridae) causes a water excess, and this is exacerbated by a low dietary intake of ions. The nectar and pollen of the preferred food-plants, Virgilia divaricata Adamson and Podalyria calyptrata Willd., and other Fabaceae had low levels of sodium. Analyses of the bees and their body fluids showed that the bees have an exceptionally low Na content, and Na homeostasis seems to depend on recycling almost all Na which enters the rectum. The copious dilute urine (137 mOsm) had Na and K concentrations of only 3.4 and 7.0 ITIM, respectively. Isolated preparations of Xylocopa Malpighian tubules secreted a fluid with a K concentration 10 times that of the haemolymph. This means that recycling of K is as important as that of Na, and the bulk of K resorption probably occurs passively in the ileum. This study is the first to examine hymenopteran Malpighian tubules. Their stimulation by cAMP is indicative of the presence of a diuretic hormone in Xylocopa.     

Specificity and localisation of lipoprotein lipase in the flight muscles of Locusta migratoria

Using natural lipoproteins as substrates, lipase activity has been measured in leg muscle, fat body, midgut and flight muscles of Locusta migratoria. The enzymic activity in the flight muscles is higher than in those other tissues tested, confirming the potential of the flight muscles to utilise lipids at high rates. In addition, a membrane-bound lipoprotein lipase can be extracted from flight muscle. The flight muscle enzyme activity shows a marked substrate specificity; at lipoprotein concentrations equivalent to those found normally in flown or resting locusts respectively, the enzyme hydrolyses diacylglycerols associated with lipoprotein A+ (present in the haemolymph of flown or adipokinetic hormone-injected locusts) at about 4 times the rate of those associated with lipoprotein Ayellow (which is the major lipoprotein in resting locusts). In addition, the hydrolysis of lipids carried by lipoprotein Ayellow is dramatically reduced in the presence of lipoprotein A+. These observations indicate that the enzyme plays a specific role in the uptake of lipids at the flight muscles to ensure a smooth transition from carbohydrate to lipid based metabolism during flight.     

Solitary invasive orchid bee outperforms co-occurring native bees to promote fruit set of an invasive Solanum

Our understanding of the effects of introduced invasive pollinators on plants has been exclusively drawn from studies on introduced social bees. One might expect, however, that the impacts of introduced solitary bees, with much lower population densities and fewer foragers, would be small. Yet little is known about the potential effects of naturalized solitary bees on the environment. We took advantage of the recent naturalization of an orchid bee, Euglossa viridissima, in southern Florida to study the effects of this solitary bee on reproduction of Solanum torvum, an invasive shrub. Flowers of S. torvum require specialized buzz pollination. Through timed floral visitor watches and two pollination treatments (control and pollen supplementation) at three forest edge and three open area sites, we found that the fruit set of S. torvum was pollen limited at the open sites where the native bees dominate, but was not pollen limited at the forest sites where the invasive orchid bees dominate. The orchid bee’s pollination efficiency was nearly double that of the native halictid bees, and was also slightly higher than that of the native carpenter bee. Experiments using small and large mesh cages (to deny or allow E. viridissima access, respectively) at one forest site indicated that when the orchid bee was excluded, the flowers set one-quarter as many fruit as when the bee was allowed access. The orchid bee was the most important pollinator of the weed at the forest sites, which could pose additional challenges to the management of this weed in the fragmented, endangered tropical hardwood forests in the region. This specialized invasive mutualism may promote populations of both the orchid bee and this noxious weed. Invasive solitary bees, particularly species that are specialized pollinators, appear to have more importance than has previously been recognized. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Quantitative studies on the release of locust adipokinetic hormone

Fractionation of methanolic extracts of haemolymph on Sephadex LH-20 made possible the measurement of the titre of adipokinetic hormone in the haemolymph of locusts. Experimentally produced high concentrations of haemolymph carbohydrate caused a delay in the mobilization of lipid during flight, and very low titres of the hormone were present in the haemolymph of locusts injected with trehalose immediately before a 25 min flight. In these locusts flight speed was higher than saline-injected controls. Although delayed lipid mobilization during flight was also seen in locusts injected with sucrose, sucrose is not utilized for flight metabolism and flight speed was not increased by the injection. Tentative estimates of the release rate (c. 1000pg/20min flight) and half life (c. 20 min) of adipokinetic hormone during flight are made. The results described suggest that during flight the rate at which trehalose disappears from the haemolymph does not play a major role in the initiation of the release of adipokinetic hormone.     

木蜂的访花行为和传粉作用

木蜂作为蜜蜂科的重要类群,是热带和亚热带地区显花植物常见的传粉者.木蜂具有访花的季节时间长、访花植物种类多、能耐高温或低光照、能嗡声传粉等特点.这些访花特点是木蜂作为热带植物、尤其是温室作物、夜间开花植物和部分茄属植物的重要传粉者.近年来国外已经证明木蜂能有效为蓝莓、西番莲、荷包豆、温室西红柿和温室甜瓜授粉,但我国有关木蜂为多数农作物传粉的重要性和有效性的证据较少.本文综述了近年来木蜂的访花行为和传粉作用的研究进展,为进一步保护、管理和利用木蜂资源提供理论依据.     

Oxygen consumption and body temperature of active and resting honeybees

We measured the energy turnover (oxygen consumption) of honeybees (Apis mellifera carnica), which were free to move within Warburg vessels. Oxygen consumption of active bees varied widely depending on ambient temperature and level of activity, but did not differ between foragers (>18 d) and middle-aged hive bees (7-10 d). In highly active bees, which were in an endothermic state ready for flight, it decreased almost linearly, from a maximum of 131.4 microl O(2) min(-1) at 15 degrees C ambient temperature to 81.1 microl min(-1) at 25 degrees C, and reached a minimum of 29.9 microl min(-1) at 40 degrees C. In bees with low activity, it decreased from 89.3 microl O(2) min(-1) at 15 degrees C to 47.9 microl min(-1) at 25 degrees C and 14.7 microl min(-1) at 40 degrees C. Thermographic measurements of body temperature showed that with increasing activity, the bees invested more energy to regulate the thorax temperature at increasingly higher levels (38.8-41.2 degrees C in highly active bees) and were more accurate. Resting metabolism was determined in young bees of 1-7 h age, which are not yet capable of endothermic heat production with their flight muscles. Their energy turnover increased from 0.21 microl O(2) min(-1) at 10 degrees C to 0.38 microl min(-1) at 15 degrees C, 1.12 microl min(-1) at 25 degrees C, and 3.03 microl min(-1) at 40 degrees C. At 15, 25 and 40 degrees C, this was 343, 73 and 10 times below the values of the highly active bees, respectively. The Q(10) value of the resting bees, however, was not constant but varied in a U-shaped manner with ambient temperature. It decreased from 4.24 in the temperature range 11-21 degrees C to 1.35 in the range 21-31 degrees C, and increased again to 2.49 in the range 30-40 degrees C. We conclude that attempts to describe the temperature dependence of the resting metabolism of honeybees by Q(10) values can lead to considerable errors if the measurements are performed at only two temperatures. An acceptable approximation can be derived by calculation of an interpolated Q(10) according to the exponential function (V(O(2))=0.151 x 1.0784(T(a))) (interpolated Q(10)=2.12).