Thermal response and reversibility of diapause in the eggs of Locusta migratoria

Abstract. Eggs of a local population of Locusta migratoria L. (Orthoptera: Acrididae) collected near Hirosaki (40.5^oN) entered diapause when incubated at temperatures between 20 and 35^oC. For diapause development the optimum temperature was 10^oC. The lower thermal threshold for post-diapause development was 14.7^oC. After chilling at 10^oC for 20 days, the rate of hatching varied with incubation temperature, being 0, 61% and 81% at 20, 25 and 30^oC, respectively. After chilling for 40 days or more, however, almost all eggs hatched at 20–30^oC. Diapause with a reduced intensity seemed to be eliminated easily by a high temperature of 25 or 30^oC.
When eggs chilled at 10^oC for 20 days were kept at 20^oC for 7 days or more before incubation at 25^oC, almost all eggs maintained diapause. Most eggs chilled at 10^oC for three 10 day periods separated by 3 days of warming at 25^oC failed to terminate diapause. Daily alternations of 10^oC (18 h) and 25^oC (6h) decreased the diapause-terminating effect of chilling. These facts suggest that diapause intensity can be restored if eggs chilled insufficiently are exposed to a moderately high temperature. This reversible change in diapause intensity would play an important role in maintaining diapause before winter.     

Influence of thermoperiod and photoperiod on reproductive diapause in Bruchidius atrolineatus (Pic) (Coleoptera, Bruchidae)

Abstract Bruchidius atrolineatus (Pic) is a common pest infesting cowpea seeds ( Vigna unguiculata Walp) in Africa. In the Sahelian zone, the adults are in reproductive diapause during the dry season. Diapause induction depends on the climatic conditions during embryonic and post-embryonic development. A strain of B. atrolineatus originating from the Niamey (13^oN) was reared in different thermoperiodic and photoperiodic conditions. In the thermoperiodic regime 40:25^oC, in continuous darkness, induction of diapause was dependent on the duration of the thermophase. Photoperiod could also influence diapause induction but the response depended on the temperature. When the beetles were reared in conditions of LD 12:12 h, 40:25^oC, for seven generations, the proportion of diapausing adults decreased and their sensitivity to photoperiod increased. In LD 14:10 h, 40:25^CC, the proportion of diapausing adults remained high regardless of the photoperiod. In these conditions, the first emerging adults were sexually active and were used for selection of a strain with a low incidence of diapause. After twelve generations, the proportion of diapausing beetles was lower than 5%. The responses of this selected strain to photo- and thermoperiods were reduced. The sensitivity of B. atrolineatus to photoperiod and thermoperiod could be controlled by genetic systems as observed in other insect species.     

Effect of temperature and photoperiod on the calling behaviour of a migratory insect, the oriental armyworm Mythimna separata

Abstract The pre-calling period (PCP), between emergence and first release of pheromone, determines the number of nights over which female Mythimna separata (Walker) (Lepidoptera: Noctuidae) can express their migratory potential. In its seasonal migrations in eastern Asia, this armyworm penetrates to latitudes at which it is unable to over-winter but at which reliable photoperiodic and temperature cues anticipate the deterioration of conditions. The effect of these environmental factors on PCP was examined in moths descended from samples collected in Nanjing (32^oN) during the summer migration. Under LD 14:10h, a reduction in temperature, from 23^oC during larval development to 18^oC from 24 h after pupation, resulted in a twofold increase in PCP compared with insects held at 23^oC. At 23^oC, short days (LD 12:12 h) extended PCP but the magnitude of the response was increased under a regime of decreasing photoperiod, from LD 15:9h, to LD 12:12 h through larval, pupal and adult development. Further experiments demonstrated that the response depended on a decrease in photoperiod from pre-pupal stage to adult emergence (the pupal period is spent below ground). A reduction of 50–60min over the 13–15 day pupal period at 23^oC was effective. The significance of decreasing photoperiods, irrespective of absolute levels, as a cue for species whose migrations traverse substantial ranges of latitude is considered and the results are discussed in relation to the genetic determination of PCP in M.separata and to its seasonal migrations in eastern China.     

Glial Alkalinization Detected In Vivo by 1H-15N Heteronuclear Multiple-Quantum Coherence-Transfer NMR in Severely Hyperammonemic Rat

Abstract: Brain [5-¹⁵N]glutamine amide protons were selectively observed in vivo by ¹H-¹⁵N heteronuclear multiple-quantum coherence-transfer NMR in spontaneously breathing, severely hyperammonemic rats during intravenous [¹⁵N]ammonium acetate infusion and the subsequent recovery period. The linewidth of brain [5-¹⁵N]-glutamine amide proton H_z increased from 36 ± 2 Hz at 3.4 h to 58 ± 6 Hz after 5.7 h of infusion, a net increase of 22 ± 6 Hz. Concomitantly, brain ammonia concentration increased from 1.7 to 3.5 ± 0.2 µmol/g and the rat progressed from grade III to grade IV encephalopathy. On recovery to grade III and decrease of brain ammonia concentration to 1.3 µmol/g, the linewidth returned to 37 ± 2 Hz. In aqueous solution, [5-¹⁵N]glutamine amide proton H_z underwent a 17-Hz linebroadening when pH was raised from 7.1 to 7.5 at 37°C, due to the increased rate of base-catalyzed exchange with water proton. Hence, linebroadening is a sensitive measure of changing intracellular pH. The 22-Hz linebroadening observed in vivo in severely hyperammonemic grade IV rats strongly suggests that the intracellular pH increases from 7.1 to about 7.4–7.5 in astrocytes where glutamine is synthesized and mainly stored. Probable mechanisms for the ammonia-induced alkalinization and decreased intraglial buffering capacity, as well as implications of the result for pathogenesis of hepatic encephalopathy, are discussed.     

Stable isotope profiles of partially migratory salmonid populations in Atlantic rivers of Patagonia

In the present study, profiles of stable isotope composition were characterized for two species with partially migratory populations in rivers along the latitudinal gradient of Patagonia, brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss . The effects of factors ( e.g. ontogeny of fishes, location, species and fasting) that may influence the stable isotope analysis (SIA) were evaluated, as was SIA evaluated as a tool to assign individual fish to their corresponding ecotype. Anadromous fishes exhibited enriched δ¹⁵N (15·2 ± 1·0‰; mean ± s . d .) and δ¹³C (−19·2 ± 1·3‰) relative to resident fishes'δ¹⁵N (8·8 ± 1·1‰) and δ¹³C (−23·2 ± 2·5‰). For both species, the difference in δ¹⁵N was larger between resident (range 6·8–10·7‰) and anadromous (range 14·3–17·8‰) fishes than that in δ¹³C. Values of δ¹³C, while not as dramatically contrasting in rainbow trout, provided a powerful anadromy marker for brown trout in the region. Increases were found in both δ¹⁵N and δ¹³C during the spawning migration of anadromous rainbow trout, most likely due to fasting. Differences in stable isotopes between location, size and species were found, suggesting different stable isotopes base levels in freshwater environments and different trophic levels and feeding location of anadromous populations. The SIA was demonstrated as a powerful tool for ecotype discrimination in Patagonian Rivers, overriding any effect of sampling location, size or species.     

Natural 13C and 15N abundance of field-collected fungi and their ecological implications

The natural abundance of ¹³C and ¹⁵N was measured in basidiocarps of at least 115 species in 88 genera of ectomycorrhizal, wood-decomposing and litter-decomposing fungi from Japan and Malaysia. The natural abundance of ¹³C and ¹⁵N was also measured in leaves, litter, soil and wood from three different sites. ¹⁵N and ¹³C were enriched in ectomycorrhizal and wood-decomposing fungi, respectively, relative to their substrates. Ectomycorrhizal and wood-decomposing fungi could be distinguished on the basis of their δ¹³C and δ¹⁵N signatures. Although there was high variability in the isotopic composition of fungi, the following isotope- enrichment factors (ε, mean±SD) of the fungi relative to substrates were observed:
ε_{ectomycorrhizal fungi/litter} = 6.1±0.4‰¹⁵N
ε_{ectomycorrhizal fungi/wood} = 1.4±0.8‰¹³C
ε_{wood-decomposing fungi/wood} = −0.6±0.7‰¹⁵N
ε_{wood-decomposing fungi/wood} = 3.5±0.9‰¹³C
The basis of isotope fractionation in C metabolism from wood to wood-decomposing fungus is discussed.     

Reproduction of the lambari Astyanax scabripinnis (Jenyns, 1842) (Pisces: Characidae) in a small stream in Southeastern Brazil

The reproduction of Astyanax scabripinnis captured bimonthly in the Cristais small stream (20^o00'03'S and 43^o56'46'W), in the Das Velhas River basin, was studied using gross anatomical and histological techniques. Standard length of females (56 ± 8 mm) was longer than males (49 ± 6 mm). The diameter of the nucleus of the primary spermatogonia was 7.5 ± 0.9  μ m and of the spermatozoon head 1.8 ± 0.4  μ m. For the females, the oogonia nuclei measured 10.2 ± 2.2  μ m and the vitellogenic oocyte nuclei measured 675.0 ± 66.7  μ m. The following stages of the reproductive cycle were established: developing, mature, partially spent/spawned and completely spent/spawned. Maximum number of males (61.3%) and females (58.2%) at the mature stage was observed during November/December. The gonadosomatic index of males and females was highest during the mature stage (2.4 ± 0.6; 7.5 ± 1.3, respectively) and decreased in subsequent stages. In females, the hepatosomatic index was highest during the developing stage (2.8 ± 0.3), and slightly decreased in the following stages. The highest stomach repletion index found for males was observed during the partially spent stage (2.0 ± 1.2), while for the females, this index varied discretely between the reproductive stages. The highest values of Fulton's condition factor were registered during the mature stage in both sexes (2.9 ± 0.4 for males; 3.0 ± 0.3 for females). The continuous reproductive period and the presence of partially spawned females during the entire sampling period indicated that the species has fractional spawning.     

Rate of Glutamate Synthesis from Leucine in Rat Brain Measured In Vivo by 15N NMR

Abstract: The rate of glutamate synthesis from leucine by the branched-chain aminotransferase was measured in rat brain in vivo at steady state. The rats were fed exclusively by intravenous infusion of a nutrient solution containing [¹⁵N]leucine. The rate of glutamate synthesis from leucine, determined from the rate of increase of brain [¹⁵N]glutamate measured by ¹⁵N NMR and the ¹⁵N enrichments of brain and blood leucine analyzed by gas chromatography-mass spectrometry, was 0.7–1.8 µmol/g/h at a steady-state brain leucine concentration of 0.25 µmol/g. A comparison of the observed fractional ¹⁵N enrichments of brain leucine (0.42 ± 0.03) and glutamate (0.21 ± 0.015) showed that leucine provides ∼50% of glutamate nitrogen under our experimental condition. From the observed rate (0.7–1.8 µmol/g) and the known K _m of the branched-chain aminotransferase for leucine (1.2 m M ), the rate of glutamate synthesis from leucine at physiological brain leucine concentration (0.11 µmol/g) was estimated to be 0.35–0.9 µmol/g/h, with leucine providing ∼25% of glutamate nitrogen. The results strongly suggest that plasma leucine from dietary source, transported into the brain, is an important external source of nitrogen for replenishment of brain glutamate in vivo. Implications of the results for treatment of maple-syrup urine disease patients with leucine-restricted diet are discussed.     

Energetics and foraging behaviour of the European seed harvesting ant Messor capitatus: I. Respiratory metabolism and energy consumption of unloaded and loaded workers during locomotion

Abstract The respiratory metabolism of workers of Messor capitatus (Latreille) was measured using standard micro-Warburg techniques on single individuals. The experiments were carried out at 10, 20, 25, 30 and 40^oC, and the respiratory quotient (RQ), measured for the same individuals at 30^oC, was found to be 0.77. The specific respiratory rate (y , in μl O₂/mg dry weight/h) could be described by the following equation: Iny = -2.24 + 0.098r -0.258 In W; where T is temperature and W is the dry weight in mg. The Q₁₀ for M. capitatus in the temperature interval 20–30^oC was 3.4, a higher value than for other ants.
The energy costs of movement and carrying were determined by using the RQ to convert the continuous measurement of CO₂ produced at 30^oC by Enfiuran anaesthetized workers ('resting metabolism'), by running workers and by workers loaded with a 20 mg weight to units of energy. The resting metabolism was 10.0±1.0 mJ/mg fresh weight/h. The cost of running ( Y in joule per km) could be described by: Y = 3.865 + 0.363 Wf , where Wf is fresh weight in mg. The cost of transport for all experiments could be expressed as 0.64 × the cost of running.     

The influence of environmental parameters on the bacterial populations of thermal springs in West Bengal, India

The physico-chemical characteristics and the bacterial populations of three thermal springs in West Bengal have been examined. The springs range in temperature from 42^o C (Saubhagya Kund) to 65^o C (Agni Kur.d). The levels of carbonate and bicarbonate alkalinity, total hardness and the ppm of chloride, phosphate and silicate as well of dissolved oxygen were measured at monthly intervals. Estimates of the bacterial populations were obtained from cultures. Water samples incubated at 37^oC for enumeration of mesophilic microbes, at 50^o C for thermo-tolerant bacteria and at 60^o for strict thermophiles. Tests for coliform organisms were carried out at 37^o C and at 50^o C.
All three springs show seasonal variation in their physico-chemical characteristics and in their bacterial populations. The cooler springs have large populations of mesophilic and thermotolerant bacteria but fewer thermophilic types. In the two hot springs (Saubhagya Kund and Swetganga), the differences of mean bacterial populations observed between 37^o and 50"C and between 50^o and 60^o C are highly significant ( P < 0.01), in the third (Agni Kund) the differences are also significant ( P < 0.01) but the population showed a rising trend with the temperature. Of the biotic and abiotic factors which could be involved in the observed seasonal variation in the bacterial populations, only the fluctuations in the phosphate levels were found to show a significant correlation (0.001 < P < 0.01).     

Hourglass and oscillator expressions of photoperiodic diapause response in the cabbage moth Mamestra brassicae

Abstract. Both oscillator and hourglass features are found in the photoperiodic response that controls the pupal winter diapause of Mamestra brassicae. The expression of oscillatory response to extended long-night cycles is temperature dependent, i.e. circadian resonance appears at 23 and 25^oC but not at 20 and 28^oC. At 20^oC, scanning of extended scotophases by a short light pulse does not reveal any clear circadian rhythmicity. However, a circadian feature of the photoperiodic response is indicated even at 20^oC by a bistability phenomenon, i.e. either one of the two dark periods in symmetrical skeleton photoperiods determines the diapause response depending on the phase angle with the preceding (entraining) light-dark cycles. At 20 and 25^oC, the incidence of diapause increases as a function of the number of light–dark cycles regardless of the cycle length (T) , if T is 24 h or 2 X 24h (with a 12 h light period). A non-diel cycle (r=36h) is less effective, suggesting that disturbance of the circadian organization partly impairs the diapause-inducing function. The inductive effect of a long night is largely affected by temperature, and becomes saturated with eight cycles at 20^oC and 14 cycles at 25^oC. Presumably, an hourglass mechanism measures the dark time, and a circadian component involved in some later sequence of the photoperiodic response may or may not be expressed depending on the mode of interaction between them.     

Countergradient variation in growth and food conversion efficiency of juvenile turbot

Growth performance of a high latitude (Norway) population of juvenile turbot Scophthalmus maximus , was superior to that of two other lower latitude populations (Scotland, France) especially at 18° and 22° C. Overall these results lend some support to the hypothesis of countergradient variation in growth. The Norwegian population had the highest estimated temperature optimum for growth ( T _opt.G, ±S.E.) (23·0±0·9°C) and food conversion efficiency ( T _opt.Ec) (17·5±0·3), followed by the French ( T _opt.G 21·1±1·0; T _opt.Ec, 16·7±0·1) population, whereas the Scottish population had the lowest optimum ( T _opt.G, 19·6±0·6; T _{opt Ec}, 16·5±0·1°C). These results have two major implications: firstly, for turbot culture, particularly in selection work focusing on growth performance; secondly, if countergradient variation in growth performance takes place within a species one cannot assume automatically that one set of physiological parameters, in this case growth-related parameters, is satisfactory to predict growth for a species throughout its range as different populations might show a difference in response towards different physiological parameters.     

A mutant strain of Chymomyza costata (Diptera: Drosophilidae) insensitive to diapause-inducing action of photoperiod

ABSTRACT. From a Japanese population of Chymomyza costata which has been known to have a photoperiodic larval diapause, we selected a mutant strain which did not respond to photoperiod. However, about 70% of the individuals of this strain entered diapause at 11^oC irrespective of photoperiod, and about the same percentage of those of the photoperiod-sensitive strain also did so in continuous illumination at 11^oC. This indicates that low temperature induces diapause independently of photoperiod. On the other hand, a temperature drop from 18 or 25^oC to 15^oC and chilling at 4^oC did not induce diapause.     

Development rates of some pre-adult stages in blowflies with reference to low temperatures

Abstract. Duration of some pre-adult stages of Calliphora vicina Robineau-Desvoidy, C.alpina Zett., C.vomitoria Linn., Phormia terraenovae R.-D. and Lucilia sericata Meig. were determined at 3.5–26^oC, in the context of use of these insects in forensic estimates of post-mortem intervals. Egg development in C. vicina occurs down to at least 3.5^oC, larval growth to 4^oC and puparial formation, development and perfect adult emergence to 5^oC. Growth curves by successive weighing of individual larvae showed specific differences in rates of development of the above species at constant temperatures. Alternating temperatures for 12 h periods (such as 10^oC and 20^oC) to simulate diurnal changes, usually, but not at all temperature pairs tested, caused acceleration of growth relative to the corresponding constant temperature (15^oC in the above case), in C.vomitoria, P.terraenovae and L.sericata , but usually caused retardation of larval growth in C.vicina. In this species, larvae as single individuals on beef liver in small tubes grew on average at the same rates as those (50–100 larvae) growing communally. All species showed variation in larval growth between individuals, more marked in C.vicina , and slower-growing larvae showed increased unexplained mortality. Because of this and to avoid complication by fast-growing larvae from later laid egg batches on a carcass, growth curves given are those of mean weights of the heaviest 25% (upper quartile) of groups of 40–90 feeding larvae. Variation in growth rates, and acceleration or retardation of growth in different species under alternating temperatures, thus affect suggested procedures in obtaining estimates of post-mortem intervals using these insects.     

Habitat selection, foraging niches and horizontal spacing of Willow Warbler Phylloscopus trochilus and Chiffchaff P. collybita in an area of sympatry

Habitat selection of the Willow Warbler and the Chiffchaff was studied along a succession of grey alder forest in Central Norway (63^oN) where both species breed. Both were found in all serai stages, but there was a slight tendency for the Willow Warbler to be found more often in the voungest stages than was the Chiffchaff.
Foraging niches and horizontal spacing were studied within one particular forest. Most of the records of both Willow Warbler and Chiffchaff came from the tree layer, and the overlap between the species in their foraging niches was considerable. However, the species were found to occupy almost mutually exclusive territories.     

Symbiotic N2 fixation in a high Alpine grassland: effects of four growing seasons of elevated CO2

1. Increasing carbon dioxide concentration (E: 680 μl CO₂ litre^–1 vs ambient, A: 355 μl CO₂ litre^–1) around late-successional Alpine sedge communities of the Swiss Central Alps (2450 m) for four growing seasons (1992–1995) had no detectable effect on symbiotic N₂ fixation in Trifolium alpinum —the sole N₂-fixing plant species in these communities (74 ± 30 mg N m^–2 year^–1, A and E plots pooled).
2. This result is based on data collected in the fourth growing season showing that elevated CO₂ had no effect on Trifolium above-ground biomass (4·4 ± 1·7 g m^–2, A and E plots pooled, n = 24) or N content per unit land area (124 ± 51 mg N m^–2, A and E pooled), or on the percentage of N Trifolium derived from the atmosphere through symbiotic N₂ fixation (%Ndfa: 61·0 ± 4·1 across A and E plots) estimated using the ¹⁵N dilution method.
3. Thus, it appears that N inputs to this ecosystem via symbiotic N₂ fixation will not be dramatically affected in the foreseeable future even as atmospheric CO₂ continues to rise.     

Effects of the East Australian Current on the genetic structure of a direct developing muricid snail (Bedeva hanleyi, Angas): variability within and among local populations

This paper examines the model that the East Australian Current (EAC) is an important determinant of genetic structure for the direct developing intertidal snail Bedeva hanleyi. Above latitude 33^o S on the east coast of Australia the EAC typically flows parallel to the shore in a southerly direction, whilst below 33^o S the direction of flow is predominantly offshore. Based on this flow-pattern it was predicted that B. hanleyi should exhibit greater genetic subdivision in the region south of 33^o S, due to smaller amounts of inter-population gene-flow via rafting. To test this hypothesis, collections of 45 individuals were made from each of 10–32 local populations/˜ 400 km region. Data for six polymorphic and apparently unlinked allozyme loci were consistent with the hypothesized effects of the EAC. Local populations from the northern region exhibited significantly more alleles per locus (mean = 2.2, cf. 1.8 for southern populations) and greater Hardy-Weinberg-expected heterozygosities (mean = 0.299, cf. 0.185 for southern populations) (one-tailed t -test; P <0.05 in each case). Moreover, the weighted jackknife ±mean SE) standardized genetic variance (θ) among southern populations (0.156 ± 0.025) was more than 50% higher than that among northern populations (0.103 ± 0.018).     

Geographical variation in AdhF and alcoholic resource utilization in Indian populations of Drosophila melanogaster

Indian geographical populations of Drosophila melanogaster, collected at latitude 10–32.3 ^oN, longitude 76.1–80.1 ^oE and altitude 16–2050 m, were analysed for changes in Adh ¹ frequency and utilization potential of diverse alcoholic resources. Until now, there have been limited data on climatic association of correlated changes on these aspects in continental populations of D. melanogaster. Indian populations demonstrate an increase in Adh ^F frequency by 0.04 per degree latitude and significantly higher utilization of ethanol (9.0–15.2%), acetic acid (8.1–12.5%), n-propanol (2.55-4.25%), 2-propanol (1.5-3.5%), n-butanol (2.15 3.5%) and 2-butanol (0.68-1.2%). Data also revealed significant correlation with latitude as well as altitude. Regression analysis of climatic data from collection sites confirmed the observed clinal variation of Adh ^F as well as alcoholic utilization in D. melanogaster. On the Indian subcontinent, variation in Adh ^F frequency and alcoholic resource utilization along increasing latitude as well as altitude are due to climatic selection factors such as temperature and rainfall.     

The optics of tsetse fly eyes in relation to their behaviour and ecology

Abstract The visual acuity of two species of tsetse flies, Glossina morsitans morsitans Westw. and Glossina pallidipes Aust., was investigated. Male G. morsitans eyes have an acute zone in the forward region, with large hexagonal lenses (mean minimum diameter, D=33, SE±0.7 μm), relatively small interommatidial angle (Δ(φ=1.08^o) and angular receptive field of individual ommatidia (Δp) of not less than 1.14^o. A narrow band of square lenses, with intermediate diameter and Δφ, merges with smaller hexagonal lenses in the periphery (24±0.7 μm), with relatively large interommatidial angle (Δφ=3.7^o) and small angular receptive field (Δp = c. 1.6^o). G.pallidipes eyes are similar, except that the lenses in the acute zone are larger than those of G.morsitans , in proportion to their larger body size. Female eyes are not significantly different from male eyes, except that they have a narrower region of binocular overlap (maximum for males = 24^o, for females = 18^o). The eye parameter (p=DΔφ) in the acute zone of male G.morsitans = 0.62, and in the peripheral zone = 1.56. These relatively high values are consistent with fast flight, visual detection of drift due to low wind speeds, mating chases and discrimination of cryptic host animals at high light intensities. The extended region of binocular overlap in males may serve as an early warning system of the approach of potential females. From our estimates, tsetse flies ought to be able to detect small objects against the sky c. 30 min before sunrise and after sunset, and to use their peripheral vision perhaps 15 min earlier and later than this.     

A note on the performance of Rappaport's medium, compared with Rappaport-Vassiliadis broth, in the isolation of salmonellas from meat products, after pre-enrichment

Salmonellas were isolated from meat products using a slightly modified Rappaport's enrichment medium (R25), Rappaport-Vassiliadis procedure (Rappaport's broth containing 10 ml instead of 30 ml of Malachite Green solution and incubated at 43^oC instead of 37^oC), and Muller-Kauffmann's tetrathionate broth. From 255 samples, 89 were found positive with the Rappaport-Vassiliadis procedure, 83 with the R25 broth, whereas only 43 were positive with Muller-Kauffmann broth. It is concluded that the R25 medium may be used as an alternative to the more effective Rappaport-Vassiliadis broth when the only available incubation temperature is 37^oC.