Variable energetic responses to clutch size manipulations in white-throated dippers Cinclus cinclus

We used the doubly-labelled water technique to measure daily energy expenditure (DEE) of a free-living uniparental incubator, the white-throated dipper Cinclus cinclus , in Scotland. DEE was 205±8 (s.e.m.) kJ d⁻¹ for 17 females incubating their natural clutch sizes, equivalent to 3.2±0.1×basal metabolic rate (BMR). To investigate the influence of clutch size on the energy budget, we measured the DEE of 14 females with clutches increased or reduced by a single egg. Birds with reduced clutch sizes had an energy expenditure with a mean and variance that did not differ from those of birds with unmanipulated clutches. Enlarging the clutch led to an increase in energy expenditure to over 4×BMR for some individuals but not for others, resulting in greater variance in energy expenditure for birds with enlarged clutches. Individual variation in energy expenditure could not be fully explained by environmental conditions, by patterns of behaviour or clutch size. Incubating females received a maximum of only 4 kJ d⁻¹ (2% of DEE) from provisioning by the male, and mobilised up to 6 kJ d⁻¹ (3% of DEE) from reserves. Females spent 2.9±0.2 h (n=20) away from the nest each day, so a foraging rate of 95 kJ h⁻¹ was required during incubation recesses to balance DEE. This 'required foraging rate' is double previous estimates of the maximum rates of energy acquisition for birds of this size. We suggest that the greater likelihood of a raised energy expenditure associated with larger clutches, combined with the difficulties in maintaining energy supplies, may constitute a constraint on avian clutch size.     

Time-activity budgets and energetics of Dipper Cinclus cinclus are dictated by temporal variability of river flow.

The white-throated Dipper (Cinclus cinclus) is unique among passerine birds by its reliance on diving to achieve energy gain in fast-flowing waters. Consequently, it should have evolved behavioural adaptations allowing responding directly to runoff patterns (one of the assumptions of the Natural Flow Regime Paradigm-NRFP). In this study (October 1998-August 2001), we investigated how behavioural and energy use strategies in Dippers might vary under the natural flow regime of snowmelt-dominated streams in The Pyrénées (France) where natural flow regime is highly seasonal and predictable. We recorded time spent in each of 5 behavioural activities of ringed birds to estimate time-activity budgets and derive time-energy budgets enabling the modelling of daily energy expenditure (DEE). Annual pattern in 'foraging' and 'resting' matched perfectly the annual pattern of the natural regime flow and there was a subtle relationship between water stage and time spent 'diving' the later increasing with rising discharge up to a point where it fell back. Thus, time-activity budgets meet the main prediction of the NRFP. For males and females Dippers, estimates of feeding rates (ratio E(obs)/E(req)=observed rate of energy gain/required foraging rate) and energy stress (M=DEE/Basal Metabolic Rate) also partly matched the NFRP. Maximum value for the ratio E(obs)/E(req) was registered in May whilst M peaked in spring. These ratios indicated that Pyrenean Dippers could face high energy stress during winter but paradoxically none during high snowmelt spates when food is expected to be difficult to obtain in the channel and when individual birds were observed spending ca 75% of the day 'resting'. Annual pattern in DEE did not match the NFRP; two phases were clearly identified, the first between January to June (with oscillating values 240-280 kJ d(-1) ind(-1)) and the second between July and December (200-220 kJ d(-1) ind(-1)). As total energy expenditure was higher during the most constraining season or life cycle, we suggest that energy management by Dippers in Pyrenean mountain streams may fit the 'peak total demand' hypothesis. At this step of the study, it is not possible to tell whether Dippers use an 'energy-minimisation' or an 'energy-maximisation' strategy.     

Effects of foraging mode and season on the energetics of the Marine Iguana, Amblyrhynchus cristatus

1. Marine Iguanas ( Amblyrhynchus cristatus ) inhabiting the rocky shores of the Galápagos Islands apply two foraging strategies, intertidal and subtidal foraging, in a seasonal climate. Effects of both foraging strategy and seasonality on the daily energy expenditure (DEE) were measured using doubly labelled water.
2. Difference in foraging mode did not result in significant differences in DEE.
3. On Santa Fé the DEE in the warm season was significantly higher than in the cool season (67·8 ± 21·8 kJ kg^–0·8 day^–1 vs 38·0 kJ kg^–0·8 day^–1). This difference can be explained by body temperature. A model estimate of the body temperature was used to predict monthly DEE figures, giving a year round budget. On average a 1-kg iguana would need only 47 kJ day^–1, or 17 mJ year ^–1. This is lower than previous estimates in which body temperatures were not taken into account.
4. The water flux of the Marine Iguana increases with increasing foraging time. The linear rise per minute foraging is roughly two times as high for subtidally foraging animals as for intertidal foragers.     

Consumption of Atlantic salmon smolts and parr by goosanders: estimates from doubly-labelled water measurements of captive birds released on two Scottish rivers

The field metabolic rates (FMRs) of nine captive goosanders, Mergus merganser , released on two Scottish rivers were estimated using the doubly-labelled water (DLW) technique. Mean (± S.E.) FMR was 2.322±0.239ml CO₂ g⁻¹ h⁻¹ and daily energy expenditure (DEE) 1939 ± 184 kJ per day. This was significantly greater (x 1.5) than previous estimates which assumed DEE to be three times the basal metabolic rate (BMR) based on regression equations predicting BMR from body mass. FMR of captives and dietary data from previous studies were used to estimate daily consumption of salmon, Salmo salar , smolts and parr by natural populations of these ducks on the river North Esk, north-east Scotland. Goosanders are likely to consume 480-522 g fish per day of which two-thirds are juvenile salmon; equivalent to a daily intake of 10-11 smolts and 48-52 parr. Annual predation of smolts by goosanders was estimated to be between 8000 and 15 000 or 3 and 16% of annual production.     

Some mechanical properties of the flagellar-pedicellar suspension in Aedes aegypti (L.)

Abstract The rotation of the flagellum of male and female Aedes aegypti (L.) was measured in a wind tunnel at wind speeds between 0 and 116cms^-1. Although the surface area of the female flagellum is only 10% of the male, it rotates through double the angle of the male flagellum for the same increase in wind speed. The larger rotation of the female flagellum could result from: a reduced resistive torque in the flagellar-pedicellar suspension; a larger antennal-positioning reflex; a smaller initial angle of attack. The resistive torque in the flagellar-pedicellar suspension was measured in both male and female Aedes aegypti. In ten adult females the average torque at 8^o rotation was 2.70 ± 1.33 times 10^-10Nm and in ten males it was 6.46 ± 3.46 times 10^-10Nm. The significance of these results is discussed with reference to the sexual dimorphism in the sensory tasks required of Johnston's organ in the two sexes.     

Moult energetics of the northern elephant seal (Mirounga angustirostris)

Northern elephant seals, Mirounga angustirostris , undergo an annual moult during which they shed all of their pelage and underlying epidermis. Moulting takes place on land and lasts a mean of 32.0±6.6 days. During this time the mean mass loss of adult females was 24.7±6.1%. Mean body composition at arrival (25.6±4.8%fat) did not differ significantly from that at departure (24.9±3.2%fat). Fat catabolism accounted for 93.6%of derived energy and 41%of mass lost. Approximately 3.5%of total mass loss was associated with the shedding of the pelage and epidermis. Moulting female northern elephant seals express an average daily metabolic rate of 2.0±0.6 times that predicted for adult terrestrial mammals. This energy demand was met by losing 3.0 kg d^-1 of total body mass. These energy expenditures suggest that, similar to data for harbour seals, the moult period is a time of relatively low energy expenditure.     

The relationship between foraging behaviour and energy expenditure in Antarctic fur seals

By using time-depth recorders to measure diving activity and the doubly-labelled water method to determine energy expenditure, the relationship between foraging behaviour and energy expenditure was investigated in nine Antarctic fur seal females rearing pups. At-sea metabolic rate (MR) (mean of 6.34 ± 0.4 W. kg^-1; 4.6 times predicted BMR) was positively correlated to foraging trip duration (mean of 4.21 ± 0.54 days; r²= 0.5, P < 0.04). There were no relationships between MR and the total number of dives, the total time spent diving or the total vertical distance travelled during the foraging trip. There was, however, a close negative sigmoidal relationship (r²= 0.93) between at-sea MR and the proportion of time at sea spent diving. This measure of diving behaviour may provide a useful, inexpensive means of estimating foraging energy expenditure in this species and possibly in other otariids. The rate of diving (m.h^-1) was also negatively related to at-sea MR (r²= 0.69, P < 0.005). Body mass gain during a foraging trip had a positive relationship to the time spent at sea (r²= 0.58, P < 0.02) and the total amount of energy expended while at sea (r²= 0.72, P < 0.004) such that, while females undertaking long trips have higher metabolic rates, the energetic efficiency with which females gain mass is independent of the time spent at sea. Therefore, within the range of conditions observed, there is no apparent energetic advantage for females in undertaking foraging trips of any particular duration.     

The arrangement of the heart chambers and associated blood vessels in the Devonian osteostracan Norselaspis glacialis. A reinterpretation based on recent studies of the circulatory system in lampreys

Food intake and digestion were investigated at four stages in the first 218 days of lactation in tammar wallabies ( Macropus eugenii ) carrying litters of one, and in non-lactating females as a control. This period of lactation in tammars, which includes the phase of exponential growth of the young, is comparable to gestation plus early lactation in ruminant placentals. Food and energy intakes by mothers remained at the non-lactating level while rate of growth of young was slow (up to Day 105 of lactation) but then rose as the growth rate of young increased, keeping pace with the predicted requirements for milk synthesis and export. There was no indication of the energy deficit seen in late gestation and early lactation in many herbivorous placental mammals. The gross efficiency of utilization of ME for growth of offspring was estimated as 13–15%, which is at least as high as values for placentals during gestation. The mean intake of metabolizable energy (ME) at 218 days was 603 kJ.kg^-0.75.d^-1, which represented 136% of ME intake by nonlactating females, or an increment of 159 kJ.kg^-0.75.d^-1. It was estimated that ME intake may rise to 773 kJ.kg^-0.75.d^-1 at peak lactation, which would be 174% of the non-lactating level or an increment of 329 kJ.kg^-0.75. d^-1. This allometrically-scaled increment is similar to values for some ruminants that use body reserves extensively to offset peak lactational food requirements. These and previously-reported trends suggest that ecologically comparable herbivorous marsupials and placentals utilize different physiological strategies to minimize demands on food resources during reproduction, but that both daily and overall demands can be similar.     

THE UPTAKE OF γ-[3H]AMINOBUTYRIC ACID BY SLICES FROM VARIOUS REGIONS OF RAT BRAIN AND THE EFFECT OF LITHIUM

Abstract— Slices from various regions of rat brain, incubated at 25°C, rapidly accumulate [³H]GABA from the surrounding medium until after 60min tissue:medium ratios as high as 300 may be achieved. Kinetic analysis has demonstrated two distinct uptake systems for GABA in all the brain regions examined. One system has a relatively high substrate affinity ( K_m = 1.2 ± 10^-5 M) while the other has a lower affinity ( K_m = 4 ± 10^-4 M). Studies at low GABA concentration (5 ± 10^-8 M), as well as estimates of maximum velocities, have shown that the distribution of the high affinity uptake system is heterogeneous. Cortex, hypothala mus, midbrain and hippocampus have relatively high uptake rates while the striatum, cerebellum and pons and medulla have a lower uptake rate. Maximum velocities for the low affinity uptake system show much less regional variation.
Lithium, either added to the incubation medium or fed to rats, had no effect on the uptake of GABA by cortical slices.     

THE IRREVERSIBLE INHIBITION OF BRAIN L-GLUTAMATE-I-DECARBOXYLASE BY (2RS,3E)-2-METHYL-3,4-DIDEHYDROGLUTAMIC ACID

Abstract— Incubation of chick embryo brain l -glutamate-1-dccarboxylase (GAD, EC 4.1.1.15) with (2RS,3E)-2-methyl-3,4-didehydroglutamic acid (MDG), a substrate analog of l -glutamic acid, results in a time-dependent irreversible inhibition of the enzymic activity. In the presence of 2.0 ± 10^-3 m inhibitor the half-life for inactivation is 11.6min. The inhibitor is a substrate for GAD and requires turnover prior to inactivating the enzyme and is therefore another example of the k _cat class of inactivator. The measured K _l is 6.6 ± 10^-4 m and the k _cat for its turnover is 1.01 ± 10^-3 s-¹ at 37°C (pH 7.2). The inhibitor has no effect on the apoenzymc or the holoenzyme treated with 1.0 ± 10^-3 m hydrazinc. Both l -and d -glutamate, but not mercaptoethanol, reduce the rate of enzymie inactivation by the inhibitor. The exceedingly high specificity implicit in the design of this inhibitor should render it useful in studies designed to uncover the physiological role of GABA.     

Performance and diacetyl production of commercial strains of malolactic bacteria in wine

This study compares 11 commercial cultures of Leuconostoc oenos and Lactobacillus plantarum in Cabernet Sauvignon, Pinot Noir and Chardonnay wines. Performance of the cultures was found to be greatly influenced by wine type. Better survival of the bacteria was observed in Cabernet Sauvignon and Pinot Noir wines. The time necessary to complete malolactic fermentation (MLF) was 65 ± 14 d for Chardonnay, 71 ± 3 d for Cabernet Sauvignon, and 25 ± 8 d for Pinot Noir. The maximal rate of malate utilization was 0·4 g d^-1 for Pinot Noir, and 0·2 g d^-1 for the two other wine types. Final diacetyl concentration was lower in Chardonnay wines (highest 0·58 mg l^-1) compared to the other wines (highest 5·8 mg l^-1). Malic and citric acid were co-metabolized by all strains. None of the strains metabolized glycerol. Significant differences in final diacetyl concentration of wine vinified with the different strains were found. Panelists could reliably differentiate MLF wines from non-MLF wines, irrespective of their diacetyl content, indicating that diacetyl is not the only important MLF flavour.     

Vasopressin-enhanced urea transport by rat inner medullary collecting duct cells in culture

Abstract. The distal inner medullary collecting duct (IMCD) is critical in the urinary concentrating process, in part because it is the site of vasopressin (AVP)-regulated permeability to urea. The purpose of these experiments was to develop a cell culture model of the IMCD on permeable structure and to characterize the responsiveness to AVP. Rat IMCD cells were grown to confluence on collagen-coated Millipore filters glued onto plastic rings. To assess the time required to achieve confluence, the transepithelial resistance was measured periodically and was found to be stable after 2 weeks, at a maximal value of 595 ± 22 ω cm². In separate monolayers the effect of AVP on inulin and urea permeability was determined. While inulin permeability was unchanged after AVP, urea permeability increased from 6.0 ± 0–4 to peak values of 16.0 ± 3–8(10nM),23.1 ± 3–9(1 μM)and28 1 ± 4–9(10μM) X 10^-6cms^-1 ( n = 24). In 10 other monolayers, after the addition of 1 mM 8-Br-cAMP, urea permeability increased from 5.1 ±0–3 to 8.1 ± 1–6 times 10^-6 cm s^-1 and, after 8-Br-cAMP +3-isobutyl-l-methylxanthine, to 12.2 ± 0–7 times 10^-6 cms^-1. We conclude that rat IMCD cells grown in culture exhibit the characteristics of a 'tight' epithelium. Inulin and urea permeability are not different in the absence of AVP, consistent with high resistance junctional complexes. Furthermore, IMCD cells retain the capacity for AVP-regulated urea permeability, a characteristic feature of this nephron segment in vivo.     

Temperature induced metabolic costs in carp, Cyprinus carpio L., during warm and cold acclimatization

The oxygen consumption of 6 carps was measured in a flow-through respirometer when water temperature was reduced from 23 to 7°C and increased from 23 to 33°C as well as from 11 to 32°C. The metabolic reaction of Cyprinus carpio L. was assessed at 3 levels: standard, routine and spontaneous. The Standard Metabolic Rate increased and the Q₁₀ decreased with rising temperatures. A quadratic relation was established between metabolic rates and temperature level. The enery exenditure above Standard Metabolic Rate induced by temperature changes was 6.65 ± 1.97 kJ kg^-0.8 d^-1 (x ± S.E., N = 6).
Costs for temperature acclimatization amounted to 29 %, 24 % and 9 % of the energy required for standard, routine and spontaneous action metabolism, respectively.

Zusammenfassung

Temperaturinduzierte Stoffwechselerhöhungen bei Karpfen , Cyprinus carpio L., während Warm- und Kaltakklimatisierung
Wir haben untersucht, wie der Stoffwechsel von Cyprinus carpio im Standard-, Routine- und Spontanniveau während einer Kalt- und Warmakklimatisierung im Bereich von 7–33 °C reagiert. Dieses Verhalten wurde mit Hilfe eines Durchfluß-Respirometers ermittelt. Die "Standard Metabolic Rate" nahm zu und der Q₁₀ verringerte sich mit steigender Temeratur.
Eine quadratische Beziehung besteht zwischen den Stoffwechselraten und dem Temperaturniveau. Die durch Temperaturänderun induzierte Stoffwechselerhöhung über die Standardrate wurde für den Meßbereich mit 6.65 ± 1.97 kJ kg^-0.8 d^-1 (x ± S.E., N = 6) ermittelt.
Der Anteil temperaturinduzierter Aufwendungen entsprach 29%, 24% und 9% des Standard-, Routine- und Spontanverbrauches an Energie.     

Biological activity of 6-(2,3,4-trihydroxy-3-methylbutylamino)purine, an oxidation product of zeatin

6-(2,3,4-Trihydroxy-3-methylbutylamino)purine was identified as an oxidation product of cis -zeatin and is biologically as active as the parent compound. A comparison of trans -zeatin, cis -zeatin and (±)-dihydrozeatin indicated that trans -zeatin and (±)-dihydrozeatin were more active in the soybean callus bioassay than cis -zeatin. Both the trans - and cis -isomers of zeatin did, however, give an optimum response at 10^-5 M. Dihydrozeatin was more active at concentrations of 10^-6 and 10^-5 M than trans -zeatin. The significance of the formation of 6-(2,3,4-trihydroxy-3-methylbutylamino)purine with respect to stereochemistry and the oxidation of cytokinins with an unsaturated isopentenyl side chain is discussed.     

Litter decomposition by slugs in mixed deciduous woodland

For the one year period considered, it is calculated that 683.5 g m^-2 plant litter entered the study area site. Of the six slugs studied, Arion intermedius Normand, the smallest species, had the highest overall consumption rate on the nine test foods (29.1 ± 0.9 mg dry wt g live wt^-1 d^-1) and the highest overall mean assimilation efficiency (72.0 + 0.9%). The mean faecal production for each of the six slug species was very similar, ranging from 8.4 to 9.9 mg dry wt g live wt^-1 d^-1. Using regression equations of food consumed on faeces produced, it is estimated that the slug fauna each year consumes 8.4% of the leaf litter input and 6.5% of the total available plant litter. Of the plant material consumed, 13.8 g dry wt m^-2 are deposited annually as faeces. The role of slugs in decomposition processes is discussed and compared with that of other soil organisms.     

Gorging response of Glossina palpalis palpalis to ATP analogues

ABSTRACT. The potencies of seventeen analogues of ATP as gorging inducers for Glossina palpalis palpalis were evaluated. The ranking for effective dose that induced half the flies to gorge (ED₅₀) was: A tetra P 5 ATP=2'd ATP ADP=2'd ADP > AMP-PNP > 3'd ATP 2'3'dd ATP > AMP-PCP > adenosine 5' triphosphate 2',3'dialdehyde AMP-CPP >> AMP. Females detect ATP and its analogues better than males. The ED₅₀ of ATP was 5 × 10^-7 M for teneral females and 1.5 × 10^-6 M for males. According to the potency order of the ATP analogues, the G.p.palpalis gustatory receptors recognizing ATP can be classified as P_2y purinoceptors.     

Identification of 4-chloroindole-3-acetic acid and indole-3-aldehyde in seeds of Pinus sylvestris

4-Chloroindole-3-acetic acid (4-Cl-IAA) and indole-3-aldehyde (IAId) have been characterized as endogenous constituents in seeds of Pinus sylvestris L. by gas chromatography-mass spectrometry. Quantitative estimates indicate that immature seeds contained 640 pg 4-Cl-IAA (g fresh weight)^-1 while mature seeds contained 340 pg (g dry weight)^-1. 4-Cl-IAA could not be detected in seeds five days after germination. The content of IAld increased from 127 pg (g dry weight)^-1 in mature seeds to 315 pg (g dry weight)^-1 after five days of germination.     

Population variables and life-history characteristics of the alligator pipefish Syngnathoides biaculeatus, in Papua New Guinea

Population structure and life-history variables of the widely distributed alligator pipefish Syngnathoides biaculeatus were characterized in Bootless Bay, Papua New Guinea over the course of 11 months. There was little evidence of seasonality with four focal populations showing no significant change in abundance. Similarly, the sex ratio remained 1:1 for all but 1 month. Reproductive males carrying eggs (148–278 mm in total length, L _T) were found in all months. Brood size was significantly, positively related to male L _T for newly laid broods only. Maximum observed brood size was 351 and mean ± s . d . brood size was 238 ± 57 for newly laid broods. Juveniles and males showed no change in mean L _T over the year while slightly smaller females were captured in November 2006 and September 2007. Males were significantly longer than females so von Bertalanffy growth coefficients were estimated separately for each sex: males L _∞= 285 mm, K = 0·82 year⁻¹ and females L _∞= 261 mm, K = 1·10 year⁻¹. These estimates suggest that this species grows rapidly and has a short-life span. In the context of growing concern about overexploitation of syngnathids, a rapid growth rate combined with year round reproductive activity suggests that the tropical S. biaculeatus may be relatively resilient with regard to fishing pressure.     

Parental energy expenditure of the male three-spined stickleback

The energy expenditure of male three-spined sticklebacks performing parental care was 12·3 and 9·9 J g⁻¹ h⁻¹ estimated by respirometry and ration manipulation, respectively. The energy expenditure of caring male sticklebacks was significantly higher than for non-caring males.     

Time-activity budgets and energetics of Dipper Cinclus cinclus are dictated by temporal variability of river flow

The white-throated Dipper (Cinclus cinclus) is unique among passerine birds by its reliance on diving to achieve energy gain in fast-flowing waters. Consequently, it should have evolved behavioural adaptations allowing responding directly to runoff patterns (one of the assumptions of the Natural Flow Regime Paradigm—NRFP). In this study (October 1998–August 2001), we investigated how behavioural and energy use strategies in Dippers might vary under the natural flow regime of snowmelt-dominated streams in The Pyrénées (France) where natural flow regime is highly seasonal and predictable. We recorded time spent in each of 5 behavioural activities of ringed birds to estimate time–activity budgets and derive time–energy budgets enabling the modelling of daily energy expenditure (DEE). Annual pattern in ‘foraging’ and ‘resting’ matched perfectly the annual pattern of the natural regime flow and there was a subtle relationship between water stage and time spent ‘diving’ the later increasing with rising discharge up to a point where it fell back. Thus, time–activity budgets meet the main prediction of the NRFP. For males and females Dippers, estimates of feeding rates (ratio E_obs/E_req = observed rate of energy gain / required foraging rate) and energy stress (M = DEE / Basal Metabolic Rate) also partly matched the NFRP. Maximum value for the ratio E_obs/E_req was registered in May whilst M peaked in spring. These ratios indicated that Pyrenean Dippers could face high energy stress during winter but paradoxically none during high snowmelt spates when food is expected to be difficult to obtain in the channel and when individual birds were observed spending ca 75% of the day ‘resting’. Annual pattern in DEE did not match the NFRP ; two phases were clearly identified, the first between January to June (with oscillating values 240–280 kJ d^− 1 ind^− 1) and the second between July and December (200–220 kJ d^− 1 ind^− 1). As total energy expenditure was higher during the most constraining season or life cycle, we suggest that energy management by Dippers in Pyrenean mountain streams may fit the ‘peak total demand’ hypothesis. At this step of the study, it is not possible to tell whether Dippers use an ‘energy-minimisation’ or an ‘energy-maximisation' strategy.