Thermoregulation of water foraging wasps (Vespula vulgaris and Polistes dominulus)

A comparison of the thermoregulation of water foraging wasps (Vespula vulgaris, Polistes dominulus) under special consideration of ambient temperature and solar radiation was conducted. The body surface temperature of living and dead wasps was measured by infrared thermography under natural conditions in their environment without disturbing the insects’ behaviour. The body temperature of both of them was positively correlated with T_a and solar radiation. At moderate T_a (22–28 °C) the regression lines revealed mean thorax temperatures (T_th) of 35.5–37.5 °C in Vespula, and of 28.6–33.7 °C in Polistes. At high T_a (30–39 °C) T_th was 37.2–40.6 °C in Vespula and 37.0–40.8 °C in Polistes. The thorax temperature excess (T_th–T_a) increased at moderate T_a by 1.9 °C (Vespula) and 4.4 °C (Polistes) per kW⁻¹ m⁻². At high T_a it increased by 4.0 °C per kW⁻¹ m⁻² in both wasps. A comparison of the living water foraging Vespula and Polistes with dead wasps revealed a great difference in their thermoregulatory behaviour. At moderate T_a (22–28 °C) Vespula exhibited distinct endothermy in contrast to Polistes, which showed only a weak endothermic activity. At high T_a (30–39 °C) Vespula reduced their active heat production, and Polistes were always ectothermic. Both species exhibited an increasing cooling effort with increasing insolation and ambient temperature.     

Metabolic rate during foraging in the honeybee

Summary The metabolic rate of free-flying honeybees, Apis mellifera ligustica, was determined by means of a novel respirometric device that allowed measurement of CO₂ produced by bees foraging under controlled reward at an artificial food source. Metabolic rate increased with reward (sugar flow rate) at the food source. In addition, there was no clear-cut dependence of metabolic rate on load carried during the visit, neither as crop load nor as supplementary weights attached to the thorax. The hypothesis that metabolic rate, as well as foraging and recruiting activities, depend on the motivational state of the foraging bee determined by the reward at the food source is discussed.Abbreviations CL crop load (fuel load at the FSS) - FC (=CL-W_c), fuel consumed during the visit - FSS food source simulator - FSS +dome, respirometric chamber - NVT non-visit time - TT titration time - VT visit time - W_c (=W_f-W_i) load carried at the end of the visit - W_f final weight of the forager - W_i initial weight of the forager     

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

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.     

Thermoregulation in endothermic dung beetles (Coleoptera: Scarabaeidae): effect of body size and ecophysiological constraints in flight

We explore the physiological constraints of body temperature as related to body mass and ambient temperature during flight in endothermic dung beetles showing a mass-related breakpoint where species show strong vs. weak endothermy. We found two different strategies in the dung beetles prior to flight; larger beetles (>1.9 g) elevate and maintain their body temperature (T(b)) at levels well above ambient temperature (T(a)) whereas smaller beetles' (<1.9 g) T(b) tends to conform with T(a). Physiological constraints analysis revealed a constant maximum tolerated temperature (in flight) of 42 degrees C and a minimum temperature for flight of around 25 degrees C. These, with body mass, may play a role in thermal niche partitioning and geographical distribution patterns.     

Balancing predation risk,social interference,and foraging opportunities in backswimmers,<Emphasis Type="Italic"> Notonecta maculata</Emphasis>

Loss of foraging opportunities and intraspecific competition for prey may be important costs of using refuges, because a hiding animal is unable to use or defend its foraging area from conspecific intrusions. Thus, animals should balance antipredator demands with other requirements in deciding when to come out from a refuge after a predators unsuccessful attack. Observations on foraging and social interactions of backswimmers Notonecta maculata suggest that foraging may be costly in terms of intraspecific agonistic interactions. When prey density is low, increasing the probability of finding a prey may require active exploration of a larger area, but this also increases the probability of encountering a competitor. After simulated exposure to predators, unfed bugs resumed feeding positions after a significantly shorter hiding period than recently fed bugs. We hypothesized that hiding time may also be reduced by recent interactions with conspecific competitors, due to an increased perceived need to defend feeding opportunities. Thus, when a predator attack occurred immediately after an agonistic conspecific interaction, backswimmers resumed feeding positions more quickly, and closer to the original position from which they were disturbed, suggesting short-term defense of particular positions. We conclude that when foraging, backswimmers balance the benefits of finding prey with the costs of predation risk and social interference in deciding their foraging strategy.Communicated by P.K. McGregor     

Pupal developmental temperature and behavioral specialization of honeybee workers (<Emphasis Type="Italic">Apis mellifera</Emphasis> L.)

Honeybees (Apis mellifera) are able to regulate the brood nest temperatures within a narrow range between 32 and 36°C. Yet this small variation in brood temperature is sufficient to cause significant differences in the behavior of adult bees. To study the consequences of variation in pupal developmental temperature we raised honeybee brood under controlled temperature conditions (32, 34.5, 36°C) and individually marked more than 4,400 bees, after emergence. We analyzed dancing, undertaking behavior, the age of first foraging flight, and forager task specialization of these workers. Animals raised under higher temperatures showed an increased probability to dance, foraged earlier in life, and were more often engaged in undertaking. Since the temperature profile in the brood nest may be an emergent property of the whole colony, we discuss how pupal developmental temperature can affect the overall organization of division of labor among the individuals in a self-organized process.     

Differences in swimming and diving abilities between two sympatric species of water shrews: <Emphasis Type="Italic">Neomys anomalus</Emphasis> and <Emphasis Type="Italic">Neomys</Emphasis><Emphasis Type="Italic">fodiens</Emphasis> (Soricidae)

Swimming and diving abilities of two syntopic species of water shrews, Neomys anomalus and Neomys fodiens, were tested in aquaria using video recordings taken from three views (lateral distant, lateral close and dorsal). The frequency and total duration of diving, as well as the mean duration of diving and floating bouts, were significantly higher in N. fodiens than in N. anomalus. Frequency of paddling during surface swimming was lower in N. fodiens than in N. anomalus. N. fodiens dived mainly for long distances at the bottom of the aquarium and performed a wider range of dive profiles than N. anomalus, which preferred rather short and shallow dives. The two species differed also significantly in their fineness ratios (describing how streamlined their bodies are) when diving. When swimming, N. fodiens had a relatively wider body and performed narrower movements with its tail than N. anomalus. These results show quantitatively and qualitatively for the first time that N. fodiens is more proficient at swimming and diving than N. anomalus. The results also help to explain the inter-specific differences in efficiency of underwater foraging, and support the idea of segregation of ecological niches of these species based on their different foraging modes (diving vs. wading).     

Effect of temperature and humidity on evaporative water loss in Anna's hummingbird (Calypte anna)

Summary Evaporative water loss (EWL), oxygen concumption , and body temperature (T_b) of Anna's Hummingbirds (Calypte anna; ca. 4.5g) were measured at combinations of ambient temperature (T_a) and water vapor density (_va) ranging from 20 to 37 °C and 2 to 27 g·m^-3, respectively. The EWL decreased linearly with increasing _va at all temperatures. The slopes of least squares regression lines relating EWL to _va at different temperatures were not significantly different and averaged-0.50 mg H₂O·m^-3·g^-2·h^-1 (range:-0.39 to-0.61). Increased _va restricted EWL in C. anna more than has been reported for other endotherms in dry air. The percent of metabolic heat production dissipated by evaporation ( ) was lower than that of other birds in dry air, but higher than that for other birds at high humidity when T_a 33 °C. When T_a>33 °C the effect of humidity on was similar to that in other birds. Calypte anna might become slightly hyperthermic at T_a>37 °C, which could augment heat transfer by increasing the T_b-T_a gradient. Body temperature for C. anna in this study was 43 °C (intramuscular) at T_as between 25 and 35 °C, which is above average for birds. It is estimated that field EWL is less than 30% of daily water loss in C. anna under mild temperature conditions (<35 °C).Abbreviations BMR basal metabolic rate - EWL evaporative water loss - percent of metabolic heat production dissipated by evaporation - ambient water vapor density - body surface water vapor density - RMR resting metabolic rate - T_a ambient-temperature - T_b body temperature - T_d dew-point temperature - TNZ thermoneutral zone - T_s body surface temperature - carbon dioxide production - oxygen consumption     

Thermoregulation in normal sleep and insomnia: the role of peripheral heat loss and new applications for digital thermal infrared imaging (DITI)

Sleepiness and changes in body temperature are temporally associated. (2) There is mounting evidence that insomnia may be caused by impaired heat loss capacity. (3) New techniques such as infrared thermal imaging may be useful tools to investigate thermoregulatory changes associated with sleep in humans.     

The importance of food quantity and quality for reproductive performance in alpine water pipits (Anthus spinoletta)

Studies relating reproduction to food availability are usually restricted to food quantity, but ignore food quality and the effects of habitat structure on obtaining the food. This is particularly true for insectivorous birds. In this study we relate measures of reproductive success, time of reproduction and nestling size of water pipits (Anthus spinoletta) to biomass, taxonomic composition and nutritional content of available food, and to vegetation structure and distance to feeding sites. Clutch size was positively correlated with the proportion of grass at the feeding sites, which facilitates foraging. This suggests that water pipits adapt their clutch size to environmental conditions. Also, pipits started breeding earlier and produced more fledglings when abundant food and a large proportion of grass were available, probably because these conditions allow the birds to gain more energy in less time. The number of fledglings was positively correlated with the energy content of available food. No significant relationships were found between feeding conditions and nestling size or the time that nestlings took to fledge. This suggests that water pipits do not invest more in individual nestlings when food conditions are favourable but rather start breeding earlier and produce more young. Taxonomic composition and nutritional content of prey were not correlated with any of the reproductive parameters, indicating that profitability rather than quality of food affects reproductive success. Received: 31 May 1996/Accepted: 12 August 1996     

A dynamic model of water gain and loss in larval Mexican bean beetle

Abstract. Quantitative effects of temperature, vapour pressure deficit, host, and larval body size were experimentally determined. A simulation model for dynamic water balance in the Mexican bean beetle, Epilachna varivestis Mulsant, is presented and parameters are estimated from laboratory data for water gain/loss equations. The model is based on water loss through the cuticle, spiracles and frass, and water gain through ingestion.     

The effects of water deprivation and salt load on water conservation efficiency in two Indian desert gerbils

Summary The effects of water deprivation and intraperitoneal salt loading on urine volume and on various urinary constituents have been examined in two gerbil species of the Rajasthan desert, the Indian desert gerbil (Meriones hurrianae Jerdon) and the Indian gerbil (Tatera indica indica Hardwicke). During summer, hydratedT. indica excreted 0.782 ml urine·100 g^-1·d^-1 which was about 60.5% higher than the volume of urine excreted by hydratedM. hurrianae (0.487 ml·100 g^-1·d^-1). During winter, both species excreted around 1.5 ml urine ·100 g^-1·d^-1. The experimental treatments caused reductions in urine volume inM. hurrianae from 40 to 76% during summer and from 35 to 71% in winter. Similar treatments inT. indica caused reductions in urine volume of 50–82% in summer and 5–60% in winter. The mean increase in urine osmolarity following various salt loading treatments inT. indica ranged from 3800 to 5761 mosmol·l^-1 and from 4034 to 6255 mosmol·l^-1 during summer and winter, respectively. The mean values of urine osmolarity for hydratedT. indica were 2831 and 3189 mosmol·l^-1 during summer and winter, respectively. InM. hurrianae salt loading treatments caused increases of urine osmolarity between 3381 and 5646 mosmol·l^-1 and between 4032 and 5434 mosmol· l^-1, during summer and winter, respectively, over the values recorded for hydrated animals (summer=3292; winter=3294 mosmol·l^-1). A maximum urine osmolarity of around 7000 mosmol·l^-1 was found in both species when subjected to 2% salt-loading treatment. The treatments used in this study increased urinary urea level in bothT. indica (3039–4056 mM) and inM. hurrianae (1900–2180 mM) compared to the level in their respective hydrated controls (T. indica=1628 mM;M. hurrianae=1372 mM). The results indicate thatT. indica may be better adapted to produce more concentrated urine thanM. hurrianae.     

Swimming restricted foraging behavior of two zooplanktivorous fishes <Emphasis Type="Italic">Pseudorasbora parva</Emphasis> and <Emphasis Type="Italic">Rasbora daniconius</Emphasis> (Cyprinidae) in a simulated structured environment

In littoral zones of aquatic systems, submerged macrophytes have marked structural variation that can modify the foraging activity of planktivores. Swimming and feeding behavior of Pseudorasbora parva and Rasbora daniconius (Cyprinidae) on their prey Daphnia pulex and Artemia salina, respectively, was studied in a series of laboratory experiments with varying stem densities. A range of stem densities was tested for each of the two species to compare the effect of simulated macrophytes on prey attack rates and swimming speed, average stem distance (D) was measured in fish body lengths for each of the two fish species. We found that, with reducing average stem distance, the attack rate decreased in the similar trend and this trend was similar for both fish species. However, the species differed in the degree to which swimming activity was hindered at increased stem densities, and this was due to species-specific differences in the distance moved with one tail beat. Therefore, we conclude that the reductions in swimming speed with reduced average stem distance are due to the differences in fish movement per tail beat.     

Thermal effects on activity patterns and behavioural switching in a concourse of foragers on Stachytarpheta mutabilis (Verbenaceae) in Papua New Guinea

Summary 1. The foraging activities of the papilionid butterflies Ornithoptera priamus poseidon and Papilio ulysses, and the solitary bee Amegilla sapiens (Apoidea, Anthophoridae) on the shrub Stachytarpheta mutabilis were studied in highland Papua New Guinea. 2. The insects' activity patterns were analysed at three sites with differing diurnal microclimate variation. O. priamus and A. sapiens foraged in the morning (after a period of basking and wing-whirring) and late afternoon when temperatures were well below daily maxima, whereas P. ulysses showed foraging peaks during the hottest part of the day. 3. Site choice by all 3 species appeared to be determined primarily by temperature, but within the limits imposed by temperature, nectar supplies probably determined which site was visited. 4. P. ulysses showed interspersed foraging and courtship behaviour, and no behavioural switching was observed for this species. At high temperatures, both O. priamus and A. sapiens ceased foraging and showed territorial and courtship behaviour. This behavioural change allowed avoidance of heat stress, and occurred even when nectar supplies were maintained at high levels. 5. Thermal effects on behavioural switching in these insects are compared with related phenomena in other bees and butterflies.     

Effects of flooding and drought on stomatal activity, transpiration, photosynthesis, water potential and water channel activity in strawberry stolons and leaves

Transpiration, xylem water potential and water channel activity were studied in developing stolons and leaves of strawberry (Fragaria × ananassa Duch.) subjected to drought or flooding, together with morphological studies of their stomata and other surface structures. Stolons had 0.12 stomata mm^–2 and a transpiration rate of 0.6 mmol H₂O m^–2 s^–1, while the leaves had 300 stomata mm^–2 and a transpiration rate of 5.6 mmol H₂O m^–2 s^–1. Midday water potentials of stolons were always less negative than in leaves enabling nutrient ion and water transport via or to the strawberry stolons. Drought stress, but not flooding, decreased stolon and leaf water potential from –0.7 to –1 MPa and from –1 to –2 MPa, respectively, with a concomitant reduction in stomatal conductance from 75 to 30 mmol H₂O m^–2 s^–1. However, leaf water potentials remained unchanged after flooding. Similarly, membrane vesicles derived from stolons of flooded strawberry plants showed no change in water channel activity. In these stolons, turgor may be preserved by maintaining root pressure, an electrochemical and ion gradient and xylem differentiation, assuming water channels remain open. By contrast, water channel activity was reduced in stolons of drought stressed strawberry plants. In every case, the effect of flooding on water relations of strawberry stolons and leaves was less pronounced than that of drought which cannot be explained by increased ABA. Stomatal closure under drought could be attributed to increased delivery of ABA from roots to the leaves. However, stomata closed more rapidly in leaves of flooded strawberry despite ABA delivery from the roots in the xylem to the leaves being strongly depressed. This stomatal closure under flooding may be due to release of stress ethylene. In the relative absence of stomata from the stolons, cellular (apoplastic) water transport in strawberry stolons was primarily driven by water channel activity with a gradient from the tip of the stolon to the base, concomitant with xylem differentiation and decreased water transport potential from the stolon tip to its base. Reduced water potential in the stolons under drought are discussed with respect to reduced putative water channel activity.     

辽西褐土施肥及养分循环再利用中长期试验Ⅴ.不同降水年景作物产量对施肥的反应和水肥交互作用

通过比较平水年 ( 1996年 ,作物生长期降水 4 5 6mm)和丰水年 ( 1998年 ,作物生长期降水 5 98mm)作物对施肥的增产反应 ,初步估算了辽西半湿润 半干旱地区水肥交互作用对作物增产的贡献 .结果表明 ,施氮肥并增加水分供给 (降水增加 ) ,作物增产 (玉米、大豆 ) 30 5 6kg·hm-2 ,其中 1996kg·hm-2 来自水肥交互作用 ,占 6 5 .3% .施NP和堆肥并增加水分供给 ,作物增产 4 70 3kg·hm-2 ,其中 15 5 4kg·hm-2 来自水肥交互作用 ,占 33% .     

Bioenergetics and thermal physiology of American water shrews (<Emphasis Type="Italic">Sorex palustris</Emphasis>)

Rates of O₂ consumption and CO₂ production, telemetered body temperature (T_b) and activity level were recorded from adult and subadult water shrews (Sorex palustris) over an air temperature (T_a) range of 3–32°C. Digesta passage rate trials were conducted before metabolic testing to estimate the minimum fasting time required for water shrews to achieve a postabsorptive state. Of the 228 metabolic trials conducted on 15 water shrews, 146 (64%) were discarded because the criteria for inactivity were not met. Abdominal T_b of S. palustris was independent of T_a and averaged 38.64±0.07°C. The thermoneutral zone extended from 21.2°C to at least 32°C. Our estimate of the basal metabolic rate for resting, postabsorptive water shrews (96.88±2.93 J g^–1 h^–1 or 4.84±0.14 ml O₂ g^–1 h^–1) was three times the mass-predicted value, while their minimum thermal conductance in air (0.282±0.013 ml O₂ g^–1 h^–1) concurred with allometric predictions. The mean digesta throughput time of water shrews fed mealworms (Tenebrio molitor) or ground meat was 50–55 min. The digestibility coefficients for metabolizable energy (ME) of water shrews fed stickleback minnows (Culaea inconstans) and dragonfly nymphs (Anax spp. and Libellula spp.) were 85.4±1.3% and 82.8±1.1%, respectively. The average metabolic rate (AMR) calculated from the gas exchange of six water shrews at 19–22°C (208.0±17.0 J g^–1 h^–1) was nearly identical to the estimate of energy intake (202.9±12.9 J g^–1 h^–1) measured for these same animals during digestibility trials (20°C). Based on 24-h activity trials and our derived ME coefficients, the minimum daily energy requirement of an adult (14.4 g) water shrew at T_a = 20°C is 54.0 kJ, or the energetic equivalent of 14.7 stickleback minnows.     

The influence of wave exposure on the foraging activity of marine otter, <Emphasis Type="Italic">Lontra felina</Emphasis> (Molina, 1782) (Carnivora: Mustelidae) in northern Chile

The marine otter Lontra felina has been said to prefer wave-exposed habitats over more protected sites in response to a greater prey abundance in exposed habitat. We examined how the foraging activity of L. felina is affected by the regime of wave exposure and prey availability at Isla Choros, northern Chile. Through focal sampling we recorded time spent by otters in foraging, the duration of dives, and the hunting success on a wave-exposed and a wave-protected site on the island. In addition, we quantified the abundance of prey in both habitats. Marine otters spent more time foraging in the wave-protected site compared with the wave-exposed habitat. Successful dives reached 26.9% in the wave-exposed habitats, and 38.2% in the wave-protected habitat. Foraging dives were 18% shorter in wave-exposed as compared with wave-protected habitat. Numerically, available prey did not differ significantly with habitat. Our results are more consistent with the hypothesis that wave-exposed habitats represent a sub-optimal habitat to foraging marine otters. Marine otters’ use of wave-exposed patches through northern and central Chile coastal areas probably reflects a low availability of suitable protected areas and greater human disturbance of more protected habitat.     

Mathematical prediction of core body temperature from environment,activity, and clothing: The heat strain decision aid (HSDA)

Physiological models provide useful summaries of complex interrelated regulatory functions. These can often be reduced to simple input requirements and simple predictions for pragmatic applications. This paper demonstrates this modeling efficiency by tracing the development of one such simple model, the Heat Strain Decision Aid (HSDA), originally developed to address Army needs. The HSDA, which derives from the Givoni-Goldman equilibrium body core temperature prediction model, uses 16 inputs from four elements: individual characteristics, physical activity, clothing biophysics, and environmental conditions. These inputs are used to mathematically predict core temperature (T_c) rise over time and can estimate water turnover from sweat loss. Based on a history of military applications such as derivation of training and mission planning tools, we conclude that the HSDA model is a robust integration of physiological rules that can guide a variety of useful predictions. The HSDA model is limited to generalized predictions of thermal strain and does not provide individualized predictions that could be obtained from physiological sensor data-driven predictive models. This fully transparent physiological model should be improved and extended with new findings and new challenging scenarios.