Standard metabolic rate of the fire ant,Solenopsis invicta Buren: effects of temperature,mass, and caste

Standard metabolic rates of S. invicta workers, males, female alates, larvae and pupae were determined using closed-system respirometry. Vdot;(O(2)) (ml h(-1)) of all castes and life stages scaled with temperature and mass. Differences between castes and life stages are discussed in light of their different life histories and the different functions of these stages within the colony. Workers, female alates, male alates, larvae and pupae had mass-specific Vdot;(O(2)) (ml O(2) g wet weight(-1) h(-1), corrected to 25 degrees C) of 0.404+/-0.023, 0.316+/-0.010, 0.674+/-0.024, 0.291+/-0.020, and 0.227+/-0.015 (mean+/-SE), respectively. Measurement of CO(2) and O(2) made possible the examination of temperature and mass effects on respiratory quotient (RQ), as well as accurate transformation of O(2) consumption to metabolic rate (&mgr;W) for comparison with other ant species. Mass-specific metabolic rates of S. invicta females and workers compare favorably with data from 17 other ant species, but metabolic rates of males (177%) and pupae (42%) fall above and below predicted rates, respectively. Several equations relating temperature and mass to Vdot;(O(2)) are presented.     

Discontinuous gas exchange in the fire ant,Solenopsos invicta Buren: Caste differences and temperature effects

The discontinuous gas exchange cycle (DGC), the cyclic release of CO(2) and uptake of O(2), were investigated in workers and female and male alates of the red imported fire ant, Solenopsis invicta Buren, using real-time CO(2) emission measurement by flow-through respirometry. All S. invicta castes displayed discontinuous emission of CO(2) in the temperature range of 15-25 degrees C, but only male alates and workers exhibited a DGC at 30 degrees C. The closed (C) and flutter (F) periods of the DGC were distinguishable in alates of both sexes at the lowest temperature, but not clearly differentiated in females at temperatures above 15 degrees C, in males above 20 degrees C, or workers at any temperature. DGC frequency increased for all castes as temperature increased, ranging from a low of 0.9+/-0.05 mHz (male alates at 15 degrees C) to 18+/-0.79 mHz (workers at 30 degrees C). O period (or burst) volumes of all castes decreased as temperature increased, and increased with body mass - this mass effect was most pronounced at lower temperatures. Q(10) values for DGC frequency (4.27, 5.81, and 5.62 for workers, female and male alates, respectively) were high compared with Q(10)'s for standard Vdot;(CO(2)). Differences in the salient characteristics of the DGC between castes are presented and discussed, and S. invicta DGC patterns are compared to known values for some other ant species.     

Inter-sexual differences in resting metabolic rates in the Texas tarantula, Aphonopelma anax

Intra-specific variation in life history and mating strategies can lead to differences in energy allocation and expenditure in males and females. This may, in turn, explain large-scale evolutionary patterns. In this study, I investigated the effects of body mass, temperature and sex on resting metabolic rates (RMRs) in sexually mature male and female tarantulas (Aphonopelma anax (Chamberlin)), a species that exhibits extreme inter-sexual differences in life history after reaching sexual maturity. RMRs were measured as rates of CO(2) production in an open-flow respirometry system at 20, 25, 30 and 35 degrees C. These temperatures are typical to what this species experiences under natural conditions. In addition, a respiratory quotient (RQ) of 0.92 was calculated from rates of CO(2) production and O(2) consumption in a closed, constant-volume respirometry system. As expected, RMRs increased with increasing temperature and body mass. However, after adjusting for the influence of body mass, males had substantially higher metabolic rates than females at each temperature. This higher metabolic rate is proposed as an adaptive strategy to support higher energetic demands for males during their active, locomotory search for females during the mating season.     

Behavioral and physiological significance of minimum resting metabolic rate in king penguins

Because fasting king penguins (Aptenodytes patagonicus) need to conserve energy, it is possible that they exhibit particularly low metabolic rates during periods of rest. We investigated the behavioral and physiological aspects of periods of minimum metabolic rate in king penguins under different circumstances. Heart rate (f(H)) measurements were recorded to estimate rate of oxygen consumption during periods of rest. Furthermore, apparent respiratory sinus arrhythmia (RSA) was calculated from the f(H) data to determine probable breathing frequency in resting penguins. The most pertinent results were that minimum f(H) achieved (over 5 min) was higher during respirometry experiments in air than during periods ashore in the field; that minimum f(H) during respirometry experiments on water was similar to that while at sea; and that RSA was apparent in many of the f(H) traces during periods of minimum f(H) and provides accurate estimates of breathing rates of king penguins resting in specific situations in the field. Inferences made from the results include that king penguins do not have the capacity to reduce their metabolism to a particularly low level on land; that they can, however, achieve surprisingly low metabolic rates at sea while resting in cold water; and that during respirometry experiments king penguins are stressed to some degree, exhibiting an elevated metabolism even when resting.     

红火蚁的巢间相容性

在室内条件下通过将红火蚁Solenopsis invicta Buren异巢不同品级的个体置于同一容器中,对红火蚁的巢间相容性进行研究。结果表明,蚁后与异巢幼蚁共处时,异巢幼蚁的羽化率为33.3%,与对照处理的38.3%(蚁后与同巢幼蚁共处)无显著差异。工蚁与异巢幼蚁共处时,异巢幼蚁的羽化率为53.7%,与对照处理的72.2%(工蚁与同巢幼蚁共处)无显著差异。蚁后与异巢工蚁共处时,异巢蚁后的存活率为45%,与对照处理的61.7%(工蚁与同巢蚁后共处)无显著差异。有翅繁殖雌蚁与异巢工蚁共处时,异巢工蚁的存活率为86.7%与对照处理的99.4%(工蚁与同巢有翅繁殖雌蚁共处)存在显著差异;异巢有翅雌蚁的存活率为22.2%,与对照处理的88.9%(工蚁与同巢有翅繁殖雌蚁共处)存在显著差异。由此可见,同区域内红火蚁异巢各品级间存在一定程度的相容性,并巢行为有可能发生。     

The energetic cost of calling in the variable field cricket, Gryllus lineaticeps

Abstract. Female preferences for conspicuous male calls have been documented in many groups. However, relatively few studies have examined the metabolic costs associated with the production of call types preferred by females. We measured the oxygen consumption of calling male Gryllus lineaticeps Stål crickets using closed chamber respirometry. Calling song was recorded concurrently. The average increase in mass-specific oxygen consumption during calling was 2.7 times basal rates of oxygen consumption, and calling males consumed approximately 1.2ml O₂g^-lh^-1. Oxygen consumption increased with increasing chirp rate and pulse duration, but not with increasing chirp duration. Females of this species prefer higher chirp rates, thus some call types that increase the male's attractiveness to females require more metabolic energy to produce.     

CYP4AB1, CYP4AB2, and Gp-9 gene overexpression associated with workers of the red imported fire ant, Solenopsis invicta Buren

Two cytochrome P450 genes, CYP4AB1 and CYP4AB2, and the Gp-9 gene were identified as being specifically overexpressed in workers of the red imported fire ant using PCR-selected subtractive hybridization and cDNA array techniques. Full-length CYP4AB1 and CYP4AB2 were cloned and sequenced. The cDNA sequences of CYP4AB1 and CYP4AB2 have open reading frames of 1389 and 1533 nucleotides encoding proteins of 463 and 511 amino acid residues, respectively. Northern blot analysis was performed to compare expression levels of CYP4AB1, CYP4AB2, and Gp-9 for different developmental stages and castes of fire ants. We demonstrate that the expression of these three genes is developmentally and caste specifically regulated in red imported fire ants. Levels of CYP4AB1 mRNA were undetectable in 3rd+4th instars, worker pupae, and alate (mixed sex) pupae; readily detectable in male and female alates; increased (approximately 3-fold) in the queens; and rose to a maximum (13-fold) in workers. Similarly, the expression of CYP4AB2 mRNA was undetectable in 3rd+4th instars, worker pupae, and alate pupae; low in male and female alates and queens; and increased (approximately 7-fold) in workers. Levels of Gp-9 mRNA were readily detectable in male alates; increased (approximately 3-fold) in female alates; and reached a maximum (approximately 12-fold) in workers. Their caste-specific overexpression suggests the functional importance of CYP4AB1, CYP4AB2, and Gp-9 in workers of the red imported fire ant.     

Energetic cost of sexual attractiveness: ultrasonic advertisement in wax moths

Pair formation in the lesser wax moth,Achroia grisella(Lepidoptera: Pyralidae), is initiated by male ultrasonic signals that attract receptive females. Individual males vary in attractiveness to females, and the most attractive males are distinguished by exaggeration of three signal characters: pulse rate, peak amplitude and asynchrony interval (temporal separation between pulses generated by movements of the left and right wings during a given wing upstroke or downstroke). Using flow-through respirometry, we measured the resting and signalling metabolic rates of males whose relative attractiveness was known. Acoustic recordings and metabolic measurements were made simultaneously, and we calculated net metabolic rates and factorial metabolic scopes as measures for the energetic cost of signalling. On average, attractive males had higher net metabolic rates and factorial metabolic scopes than unattractive ones, but many unattractive males also had high values. Thus, high expenditure of energy on signalling is necessary but not sufficient for attractiveness. This may result because only one of the three signal characters critical for female preference, pulse rate, is correlated with energy expenditure. Although the results are consistent with the good genes model of sexual selection, they do not conflict with other indirect or direct mechanisms of female choice.     

蚁巢表层土壤温湿度对不同发育阶段红火蚁数量的影响(英文)

红火蚁一种攻击性非常强的外来入侵蚂蚁,可对入侵地的农业生产、生态系统、人体健康和公共安全等产生负面影响,温度和湿度是影响其生长和发育的重要环境因子.本研究评估了红火蚁蚁巢表层土壤温、湿度对红火蚁幼虫、有翅蚁蛹和有翅蚁成虫数量的影响.结果表明,随着土壤温度的升高,幼虫、有翅蚁蛹和有翅蚁成虫的数量都呈先升高后下降的趋势.当...     

Effect of queen number on the production of sexuals in natural populations of the fire ant, Solenopsis invicta

ABSTRACT. To determine whether the production of sexuals in the fire ant, Solenopsis invicta Buren, is related to queen number in the field, the numbers of sexuals in monogyne (M) and polygyne (P) colonies of this species were compared. Large colonies ( n =25 M and 25 P) were collected at random during spring, summer and fall when sexuals are actively produced, and the numbers of sexuals present were counted. The numbers of alates plus sexual pupae and larvae in M colonies far exceeded those in P colonies in each season. Significant differences between M and P colonies were also found when the numbers of alates and sexual immatures (pupae + larvae) were compared separately in each season. In addition, M colonies contained significantly more female sexuals (alates + pupae) than did P colonies in the summer and fall, and significantly more males in all three seasons. The negative relationship between queen number and number of sexuals provides evidence that queen control over the production of sexuals, previously established in laboratory experiments, also occurs under natural conditions.     

Intersexual differences in energy expenditure of Anolis carolinensis lizards during breeding and postbreeding seasons

Although the amount of energy that males and females invest in reproduction is an integral component of theories explaining the evolution of particular mating strategies, few studies have actually determined the amount of energy that each sex allocates to reproduction. We compared how energy is expended by male and female Anolis carolinensis lizards during both the breeding and postbreeding seasons. We used laboratory respirometry to determine resting metabolic rates (RMRs) of inactive, freshly captured lizards and the doubly labeled water technique to determine field metabolic rates (FMRs) of free-ranging lizards. Both RMRs and FMRs were influenced by body mass but not by sex. Season did not influence FMRs; however, RMRs of both sexes increased approximately 40% from the breeding to the postbreeding season. The seasonal increase in RMRs was attributed to a postreproductive increase in feeding rate and specific dynamic action. We used RMRs, FMRs, and thermal profiles of lizards to calculate energy budgets for breeding and postbreeding seasons. Energy budgets partitioned daily field energy (DFE; calculated from FMRs) into daily activity energy (DAE) and daily resting energy (DRE; calculated from RMRs). Energy expended for reproduction was estimated as DAE during the breeding season plus egg production (for females). Despite males having 40% greater body mass, females expended 46% more energy for reproduction than did males (906 and 619 J/d, respectively). Total metabolizable energy (TME=DFE+egg production for females) expended during the breeding season was similar for males and females (1,280 and 1,365 J/d, respectively). Although TME of females decreased 44% from the breeding to the postbreeding season (1,365 vs. 766 J/d), TME of males was similar during both seasons (1,280 vs. 1,245 J/d). There were both seasonal and sexual differences in DRE and DAE. Compared with most lizards from semiarid/desert habitats, A. carolinensis in a temperate habitat expends more total energy during the breeding season, allocates more energy to eggs, and appears to have more total energy available for reproduction.     

Metabolic rate variation in Glossina pallidipes (Diptera: Glossinidae): gender, ageing and repeatability

Despite the importance of metabolic rate in determining flight time of tsetse and in mediating the influence of abiotic variables on life history parameters (and hence abundance and distribution), metabolic rate measurements and their repeatability have not been widely assessed in these flies. We investigate age-related changes in standard metabolic rate (SMR) and its repeatability, using flow-through respirometry, for a variety of feeding, gender and pregnancy classes during early adult development in laboratory-reared individuals of the tsetse fly, Glossina pallidipes. Standard metabolic rate (144-635 microW) was generally within 22% of previous estimates, though lower than the values found using closed system respirometry. There was no significant difference between the genders, but metabolic rate increased consistently with age, probably owing to flight muscle development. Repeatability of metabolic rate was generally high (r=0.6-.09), but not in younger teneral adults and pregnant females (r approximately equal to 0.05-0.4). In these individuals, low repeatability values are a consequence of muscle or in utero larval development. Tsetse and other flies generally have a much higher metabolic rate, for a given size, than do other insect species investigated to date.     

Fasting metabolism in Antarctic fur seal (Arctocephalus gazella) pups.

The metabolism of 52-73-day old Antarctic fur seal pups from Bird Island, South Georgia, was investigated during fasting periods of normal duration while their mothers were at sea foraging. Body mass decreased exponentially with pups losing 3.5-3.8% of body mass per day. Resting metabolic rate also decreased exponentially from 172-197 ml (O2) x min(-1) at the beginning of the fast and scaled to M(b)(0.74) at 2.3 times the level predicted for adult terrestrial mammals of similar size. While there was no significant sex difference in RMR, female pups had significantly higher (F(1,18)=6.614, P<0.019) mass-specific RMR than male pups throughout the fasting period. Fasting FMR was also significantly (t(15)=2.37, P<0.035) greater in females (823 kJ x kg(-1) x d(-1)) than males (686 kJ x kg(-1) x d(-1)). Average protein turnover during the study period was 19.3 g x d(-1) and contributed to 5.4% of total energy expenditure, indicating the adoption of a protein-sparing strategy with a reliance on primarily lipid catabolism for metabolic energy. This is supported by observed decreases in plasma BUN, U/C, glucose and triglyceride concentrations, and an increase in beta-HBA concentration, indicating that Antarctic fur seals pups adopt this strategy within 2-3 days of fasting. Mean RQ also decreased from 0.77 to 0.72 within 3 days of fasting, further supporting a rapid commencement of protein-sparing. However, RQ gradually increased thereafter to 0.77, suggesting a resumption of protein catabolism which was not substantiated by changes in plasma metabolites. Female pups had higher TBL (%) than males for any given mass, which is consistent with previous findings in this and other fur seal species, and suggests sex differences in metabolic fuel use. The observed changes in plasma metabolites and protein turnover, however, do not support this.     

深圳市红火蚁婚飞规律研究

本研究利用自制红火蚁Solenopsis invicta Buren收集装置对红火蚁婚飞规律进行研究,结果表明:本试验过程中共观察到婚飞273次,无论大、中、小蚁巢均有有翅蚁婚飞现象;共收集到有翅蚁10 618头,雌雄比为2.1:1;单次婚飞有翅蚁均为雌虫的有167次,均为雄虫的有25次,单次婚飞有翅蚊既有雌虫又有雄虫(雌虫+雄虫)的共81次;同一蚁巢可以发生多次婚飞,同一蚁巢不同次婚飞的有翅蚁性别比也会发生变化;除2009年11月和2010年2月未收集到有翅蚁,其余各月均可观察到有翅蚁婚飞,婚飞最高峰期为2010年4月和5月,其次是2009年6-9月,婚飞次数和收集到的有翅蚁数量成明显的正向相关关系;8:30-15:00均有有翅蚁婚飞,而婚飞高峰期为11:30-13:30,婚飞一般持续30～150 min.婚飞一般发生在雨后晴天或相对低温后气温快速回升以后.     

Energetic costs and thermoregulation in northern fur seal (Callorhinus ursinus) pups: the importance of behavioral strategies for thermal balance in furred marine mammals

Behavioral thermoregulation represents an important strategy for reducing energetic costs in thermally challenging environments, particularly among terrestrial vertebrates. Because of the cryptic lifestyle of aquatic species, the energetic benefits of such behaviors in marine endotherms have been much more difficult to demonstrate. In this study, I examined the importance of behavioral thermoregulation in the northern fur seal (Callorhinus ursinus) pup, a small-bodied endotherm that spends prolonged periods at sea. The thermal neutral zones of three weaned male northern fur seal pups (body mass range = 11.8-12.8 kg) were determined by measuring resting metabolic rate using open-flow respirometry at water temperatures ranging from 2.5° to 25.0°C. Metabolic rate averaged 10.03 ± 2.26 mL O?kg?1 min?1 for pups resting within their thermal neutral zone; lower critical temperature was 8.3° ± 2.5°C , approximately 8°C higher than the coldest sea surface temperatures encountered in northern Pacific waters. To determine whether behavioral strategies could mitigate this potential thermal limitation, I measured metabolic rate during grooming activities and the unique jughandling behavior of fur seals. Both sedentary grooming and active grooming resulted in significant increases in metabolic rate relative to rest (P = 0.001), and percent time spent grooming increased significantly at colder water temperatures (P < 0.001). Jughandling metabolic rate (12.71 ± 2.73 mL O?kg?1 min ?1) was significantly greater than resting rates at water temperatures within the thermal neutral zone (P < 0.05) but less than resting metabolism at colder water temperatures. These data indicate that behavioral strategies may help to mitigate thermal challenges faced by northern fur seal pups while resting at sea.     

In situ measurement of calling metabolic rate in an Australian mole cricket, Gryllotalpa monanka

Examination of the energetics of sound production usually requires measurement of species that will produce normal calls under unnatural circumstances. Such measurements are potentially compromised by stress-related changes in calling input (through a reduction in calling effort) or output (through forced use of sub-optimal singing burrows). To determine if such measurements are indeed affected by abstraction from a natural setting, we measured the energetics of song production in undisturbed mole crickets Gryllotalpa monanka and employed a new approach where the animal's singing chamber replaces the respirometry chamber normally used in studies of this type. It was therefore possible to measure metabolic rate (MR) of calling crickets in situ for animals within self-constructed burrows under natural conditions. Calling MR measured under these conditions averaged 13.5-fold higher than standard MR and 2.2-fold higher than MR measured during burrowing in the lab. The calling MR of G. monanka was similar to that measured for other calling insects, and to endothermic insects, but was only 10% of that allometrically predicted for a similarly sized insect (0.89 g) during flight. A male mole cricket is estimated to consume 5.9 ml of oxygen during construction of a calling burrow and a 1-h calling bout; by comparison, a flying female would consume a similar volume in less than 6 min.     

In situ measurement of calling metabolic rate in an Australian mole cricket, Gryllotalpa monanka.

Examination of the energetics of sound production usually requires measurement of species that will produce normal calls under unnatural circumstances. Such measurements are potentially compromised by stress-related changes in calling input (through a reduction in calling effort) or output (through forced use of sub-optimal singing burrows). To determine if such measurements are indeed affected by abstraction from a natural setting, we measured the energetics of song production in undisturbed mole crickets Gryllotalpa monanka and employed a new approach where the animal's singing chamber replaces the respirometry chamber normally used in studies of this type. It was therefore possible to measure metabolic rate (MR) of calling crickets in situ for animals within self-constructed burrows under natural conditions. Calling MR measured under these conditions averaged 13.5-fold higher than standard MR and 2.2-fold higher than MR measured during burrowing in the lab. The calling MR of G. monanka was similar to that measured for other calling insects, and to endothermic insects, but was only 10% of that allometrically predicted for a similarly sized insect (0.89 g) during flight. A male mole cricket is estimated to consume 5.9 ml of oxygen during construction of a calling burrow and a 1-h calling bout; by comparison, a flying female would consume a similar volume in less than 6 min.     

Accelerometry estimates field metabolic rate in giant Australian cuttlefish Sepia apama during breeding

1. Estimating the metabolic rate of animals in nature is central to understanding the physiological, behavioural and evolutionary ecology of animals. Doubly labelled water and heart-rate methods are the most commonly used approaches, but both have limitations that preclude their application to some systems. 2. Accelerometry has emerged as a powerful tool for estimating energy expenditure in a range of animals, but is yet to be used to estimate field metabolic rate in aquatic taxa. We combined two-dimensional accelerometry and swim-tunnel respirometry to estimate patterns of energy expenditure in giant Australian cuttlefish Sepia apama during breeding. 3. Both oxygen consumption rate (Vo2) and swimming speed showed strong positive associations with body acceleration, with coefficients of determination comparable to those using similar accelerometers on terrestrial vertebrates. Despite increased activity during the day, field metabolic rate rarely approached Vo2, and night-time Vo2 was similar to that at rest. 4. These results are consistent with the life-history strategy of this species, which has a poor capacity to exercise anaerobically, and a mating strategy that is visually based. With the logistical difficulties associated with observation in aquatic environments, accelerometry is likely to prove a valuable tool for estimating energy expenditure in aquatic animals.     

The power of feeder-mask respirometry as a method for examining hummingbird energetics

Many birds spend important portions of their time and energy flying. For this reason, quantification of metabolic rates during flight is of crucial importance to understanding avian energy balance. Measurement of organismal gas exchange rates using a mask enclosing the whole head or respiratory orifices has served as an important tool for studying animal energetics because it can free the rest of the body, permitting movement. Application of so-called “mask respirometry” to the study of avian forward flight energetics presents unique challenges because birds must be tethered to gas analysis equipment thus typically necessitating use of a wind tunnel. Resulting potential alterations to a study organism's behaviour, physiology, and aerodynamics have made interpretation of such studies contentious. In contrast, the study of hovering flight energetics in hummingbirds using a specialized form of mask respirometry is comparatively easy and can be done without a wind tunnel. Small size, hovering flight, and a nectarivorous diet are characteristics shared by all hummingbird species that make these birds ideally suited for this approach. Specifically, nectar feeders are modified to function as respirometry masks hummingbirds voluntarily respire into when hover-feeding. Feeder-mask based respirometry has revealed some of the highest vertebrate metabolic rates in hovering hummingbirds. In this review I discuss techniques for the successful measurement of metabolic rate using feeder-mask respirometry. I also emphasize how this technique has been used to address fundamental questions regarding avian flight energetics such as capacities for fuel use and mechanisms by which ecology, behaviour and energy balance are linked.     

Flight modes in migrating European bee-eaters: heart rate may indicate low metabolic rate during soaring and gliding

Background

Many avian species soar and glide over land. Evidence from large birds (m _b>0.9 kg) suggests that soaring-gliding is considerably cheaper in terms of energy than flapping flight, and costs about two to three times the basal metabolic rate (BMR). Yet, soaring-gliding is considered unfavorable for small birds because migration speed in small birds during soaring-gliding is believed to be lower than that of flapping flight. Nevertheless, several small bird species routinely soar and glide.

Methodology/Principal Findings

To estimate the energetic cost of soaring-gliding flight in small birds, we measured heart beat frequencies of free-ranging migrating European bee-eaters (Merops apiaster, m _b∼55 g) using radio telemetry, and established the relationship between heart beat frequency and metabolic rate (by indirect calorimetry) in the laboratory. Heart beat frequency during sustained soaring-gliding was 2.2 to 2.5 times lower than during flapping flight, but similar to, and not significantly different from, that measured in resting birds. We estimated that soaring-gliding metabolic rate of European bee-eaters is about twice their basal metabolic rate (BMR), which is similar to the value estimated in the black-browed albatross Thalassarche (previously Diomedea) melanophrys, m _b∼4 kg). We found that soaring-gliding migration speed is not significantly different from flapping migration speed.

Conclusions/Significance

We found no evidence that soaring-gliding speed is slower than flapping flight in bee-eaters, contradicting earlier estimates that implied a migration speed penalty for using soaring-gliding rather than flapping flight. Moreover, we suggest that small birds soar and glide during migration, breeding, dispersal, and other stages in their annual cycle because it may entail a low energy cost of transport. We propose that the energy cost of soaring-gliding may be proportional to BMR regardless of bird size, as theoretically deduced by earlier studies.