Practical aspects of fumonisin production under laboratory conditions

Studies were performed to develop an efficient method for fumonisin toxin production in sufficient quantities for animal toxicological experiments, on the basis of three earlier published fumonisin toxin production methods. Three absolutely necessary factors were taken into account and tested in a serial experiment. TheFusarium verticillioides strain MRC 826 was directly inoculated onto soaked, autoclaved, whole maize kernels (50 g/1.71 jar). The inoculation was performed by standard spore suspension (l×l0⁶/ml), a 5/2 surface/volume culture was prepared and incubated at 25 °C for 5 weeks. To maintain the optimal a_w of approximately 1.00, the evaporated water was re-filled weekly. A final concentration of 4454±1060.9 ppm fumonisin B₁ was reached, with good repeatability. In the laboratory practice, consistent production of constant amounts of FB₁ can be obtained by applying the above settings.     

Some aspects of the isopropylidenation of d-glucitol under neutral conditions

Isopropylidenation of d-glucitol (1) under neutral conditions, by treatment with 2,2-dimethoxypropane in 1,2-dimethoxyethane, has been studied. An improved procedure for the isolation of 1,2:5,6-di-O-isopropylidene-d-glucitol, the main equilibrium product, by direct crystallisation or via the 3,4-dibenzoate is described. Some aspects of the reaction are discussed and compared with results obtained previously from the isopropylidenation of 1 in the presence of zinc chloride.     

Comparison of sexual compatibility between laboratory and wild Mexican fruit flies under laboratory and field conditions

The sexual compatibility between laboratory (LF) and wild (WF) strains of the Mexican fruit fly, Anastrepha ludens (Loew), was analyzed using analogous methodologies and experimental arenas under both laboratory and field conditions. Sexual compatibility was quantified with the following indices: the isolation index (ISI), male relative performance index (MRP), female relative performance index (FRPI), and the relative sterility index (RSI). ISI detected a certain level of incompatibility between strains under both laboratory and field conditions, because LF females tended to mate with LF males. LF mating performance was higher under laboratory than under field conditions. The relative performance indices for LF and the relative sterility index were higher in the laboratory than in the field. Differences between LF and WF in the times that males started calling and mating were observed in both environments. Importantly, WF males reduced their sexual activity under laboratory environments, whereas LF maintained similar activity levels in both conditions. The possible applications of the above-mentioned methods, not only to assess fly quality but also to determine the suitability of conditions in mass-rearing facilities, are discussed. Correlating laboratory quality to sexual behavior may contribute in the development of environmental parameters for mass-rearing facilities.     

Clutch size decisions of a gregarious parasitoid under laboratory and field conditions

Under field conditions, insect parasitoids probably experience lower rates of host encounter and life expectancy than under optimal conditions in laboratory studies. We examined the clutch size response of Mastrus ridibundus, a gregarious idiobiont parasitoid of codling moth, Cydia pomonella, cocoons, to variation in both host encounter rate and life expectancy as possible explanatory variables in a comparison of brood size in the field and laboratory. Under laboratory conditions, mean clutch size (number of eggs laid) declined from 5.8 to 3.4 as host encounter rate increased from one to eight cocoons per day. In contrast, when we reduced life expectancy by withholding honey as a food source, females did not adjust clutch size. Mean brood size (number of progeny surviving to pupation) of females foraging in walnut orchards (3.9) was significantly greater than that under laboratory conditions with excess hosts (3.1). Brood size also increased with host size in the field, but not under laboratory conditions. Brood size fitness curves were derived using both host-finding ability in the field and lifetime fecundity under laboratory conditions as indices of female fitness. Host-finding ability increased exponentially with body size, generating an estimated Lack brood size of 4.3, but lifetime fecundity increased linearly with body size, giving a Lack brood size estimate of 5.5. Under field conditions, female M. ridibundus produced brood sizes that closely approximated the Lack brood size estimated from host-finding ability, but that were significantly smaller than that estimated from lifetime fecundity. These observations suggest that, in contrast to lifetime fecundity measures from the laboratory, host-finding ability in the field provides a more accurate estimate of lifetime reproductive success for parasitoids with a low expectation of future reproduction. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Some aspects of laboratory cometary models

In this paper, we discuss some aspects of laboratory experiments proposed in the literature, associated with the chemical reactions that may occur in the comets. These comments are made in the light of the use of energetic particles or radiation as energy sources, relevant chemical reactions and compounds detected in those experiments.     

Some aspects of animal-to-human approximation of low frequency electromagnetic field exposure conditions

Appropriateness of representation of a biological object surface as an equipotential surface has been proved for conditions of a quasistatic exposure to EMF of frequencies lower than 1 MHz. The conditions, at which a self capacitance of a biological object is its basic electrical parameter, have been considered. A factor of animal-to-human approximation of low-frequency EMF exposure conditions was estimated on the basis of equal dose loading in biological objects of different geometric sizes.     

Equivalent inbreeding depression under laboratory and field conditions in a tree-hole-breeding mosquito

Understanding the consequences of inbreeding has important implications for a wide variety of topics in population biology. However, most studies quantifying the effects of inbreeding are performed under artificial farm, greenhouse, laboratory or zoo conditions. Although several authors have argued that the deleterious effects of inbreeding (inbreeding depression) are likely to be more severe under natural field conditions than in artificial experimental environments, these arguments are usually speculative or based on indirect comparisons. We quantified the effects of inbreeding on fitness traits in a tree-hole-breeding mosquito Aedes geniculatus) under near-optimal laboratory conditions and in three natural tree holes. Our index of fitness (Ro) was lower in the field than in the laboratory and declined due to inbreeding in both However, environments, we found no significant interactions between inbreeding depression and environmental conditions. In both the field and laboratory a 10% increase in the inbreeding coefflicient (F) led to a 12-15) decline in fitness (Ro) These results suggest that inbreeding depression will not necessarily be more extreme under natural field conditions than in the laboratory.     

Effectiveness of Metarhizium anisopliae formulations against dengue vectors under laboratory and field conditions

The oviposition behaviour of Aedes aegypti and the effectiveness of Metarhizium anisopliae conidia formulated in water or oil-in-water against A. aegypti adults and eggs were tested in multi-choice and no-choice tests in oviposition devices under laboratory conditions. Both females and males rested in the devices, regardless of the formulation, and were not repelled by the presence of conidia (up to 10⁶?conidia/cm²) without oil or formulated with oil on treated filter paper arranged in the device. However, at higher oil concentrations (≥0.1?μl/cm²), regardless of the presence of conidia, the number of eggs laid by gravid females on the filter paper dropped. The susceptibility of adults, especially of males, to fungal infection increased up to a 15-day incubation. An elevated number of larvae (≥41%) eclosed from eggs laid on the moistened filter paper in the device even without submersion of eggs in water, and these larvae subsequently died. In the laboratory, 1?μl/cm² oil combined with 10⁶?conidia/cm² clearly reduced eclosion to 1.8% after submersion of eggs in water compared to ≥13% eclosion in the control. In field tests in Goiânia, Brazil, eclosion of aedine larvae from eggs laid on filter paper previously treated with oil-in-water formulated conidia dropped to between 0% and 36% compared to 22–50% in the control. Promising results of laboratory and field tests with M. anisopliae formulated in water or oil-in-water and tested in a device emphasised the effectiveness of a fungus-based formulation for aedine mosquitoes in peridomestic areas.     

Ammonium uptake by field-grown Eriophorum vaginatum roots under laboratory and simulated field conditions

Nitrogen (N) deficiencies in tundra ecosystems could be caused, in part, by the kinetics of root N uptake. The objectives of this study were to quantify NH₄ uptake by field-grown excised roots of Eriophorum vaginatum I. under controlled NH₄ concentrations (0-250 μmol I^-1) and temperatures (5-20°C) and to evaluate this laboratory derived model as a means of estimating field NH₄ uptake. There was no consistent temperature effect on root NH₄ uptake which suggests a relative in-sensitivity of E. vaginatum roots to short-term temperature fluctuations. The Michaelis-Menten equation parameters for NH₄ uptake were V_max= 22.1 μmol h^-1 g^-1 and K_m= 191 μmol I^-1. Using field NH₄ concentrations, field E. vaginatum root biomass data, and the Michaelis-Menten equation, an estimate was made of NH₄ uptake over a 42 day period; this estimate of NH₄ uptake accounted for 28% of the net incorporation of N into leaves and roots which is a reasonable estimate for E. vaginatum which relies primarily on N retranslocation for supplying new leaves and roots. Major uncertainties in field N uptake rates, model parameterization, and site characterization preclude an accurate model validation and indicate research areas most in need of future study.     

Feeding and breeding aspects of Stomoxys calcitrans (Diptera: Muscidae) under laboratory conditions

Bionomic aspects of Stomoxys calcitrans (Linnaeus, 1758) (Diptera: Muscidae) were studied under laboratory conditions. For this reason, laboratory-rearing techniques were optimized at the National Veterinary School of Toulouse. The colony was maintained at 25 ± 2 °C, 50 ± 10% RH under a 12-hour light cycle and observed daily. The size of each adult cage is 30 x 30 x 30 cm and designed to house about 500-1,000 flies. The average cycle from egg to adult was 19.2 ± 1.7 days. The mean longevity of imagos was 9.3 ± 5.8 days and not significantly different between sexes. Stable flies were split into two groups; the first was fed with blood, honey and water, and the second was fed only with honey and water. The mean weight of a blood meal was 11.1 ± 3.8 mg with no significant differences between males and females. The mean longevity of non-blood fed flies was found to be significantly higher (10.4 ± 3.9 days) than those fed with blood. The maximum lifespan was shorter for non-blood fed males (17 days) and females (18 days) than for those fed with blood (females: 24 days, males: 23 days). Under these laboratory conditions, S. calcitrans rearing was successfully established. In the end, the number of expected generations of S. calcitrans and the net reproduction rate were estimated to be 11.8 generations/year and 16.2 living females per female respectively.     

Gas exchange responses of Chesapeake Bay tidal marsh species under field and laboratory conditions

Summary Laboratory and field gas exchange measurements were made on C₃ (Scirpus olneyi Gray) and C₄ (Spartina patens (Ait.) Mahl., Distichlis spicata (L.) Green) species from an irregularly flooded tidal marsh on the Chesapeake Bay. Laboratory measurements were made on plants grown from root stocks that were transplanted to a greenhouse and grown under high light and high nutrient conditions. The two C₄ species were similar in their laboratory gas exchange characteristics: both had higher net carbon exchange rates, higher mesophyll conductances, higher photosynthetic temperature optima and lower leaf conductances than the C₃ species. The laboratory photosynthetic water use efficiency of the C₄ species was approximately three times that of the C₃ species.Field gas exchange responses of the above species were measured in situ a Chesapeake Bay tidal marsh. Despite differences in biological potential measured in the laboratory, all three species had similar in situ carbon exchange rates on a leaf area basis. On a dry weight basis, leaves of the two C₄ species had about 1.4 times higher light saturated CO₂ assimilation rates than the C₃ species. Light saturation of CO₂ exchange occurred at photosynthetic photon flux densities of 80 n Einstein cm^-2s^-1, compared with 160 n Einstein cm ^-2s^-1 in the laboratory grown plants. Spartina patens and Scirpus olneyi had similar daily CO₂ assimilation rates, but the daily transpiration rate of the C₃ species was almost twice that of the C₄ species. Spartina patens showed greater seasonal decrease in photosynthesis than Distichlis spicata and Scirpus olneyi. The two C₄ grass species maintained higher mesophyll conductances and photosynthetic water use efficiencies than the C₄ sedge.     

Calling behaviour of the potato aphid Macrosiphum euphorbiae oviparae under laboratory and field conditions

Abstract.  1. The calling behaviour of virgin oviparae of the potato aphid Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) was studied at three different constant temperatures under laboratory conditions. The mean age of calling for the first time decreased with a decrease in temperature from 2.9 days at 20 °C to 2.1 days at 10 °C. At all temperature regimes, the mean onset time of calling advanced from about 5 to 3 h after the onset of the photophase, and the mean time spent calling increased by > 4 h over the 8 days.
2. Cohorts of oviparae were also observed at two different periods in late summer–early autumn in the field, to examine the effects of fluctuating abiotic conditions (temperatures, wind velocity, rain) and age on calling behaviour. As under constant laboratory conditions, the mean age of calling for the first time declined with declining temperature, from 3.7 days in early September to 1.6 days at the end of September. Age-related changes in the mean onset time of calling and the mean time spent calling were much less evident under field conditions, due to the inhibitory effects of low temperatures, high winds, and rain on female calling activity.
3. The results are discussed within the context of reproductive success and address a previously proposed hypothesis suggesting that species-specific calling windows may serve as a reproductive isolating mechanism for sympatric aphid species.     

Physiological responses of Corythucha ciliata adults to high temperatures under laboratory and field conditions

Under high temperature conditions, insects can tolerate to survive through various physiological mechanisms, which have been well documented in laboratory studies. However, it is still unclear as to whether these laboratory data can scale up to those in the field. Here we studied dynamics of heat-induced metabolites in Corythucha ciliata adults under both laboratory and field conditions to examine their significance in thermal tolerance of the species. We compared the effects of controlled thermal treatments (2 h at 33–43 °C at 2 °C intervals in the laboratory) and naturally increasing thermal conditions (10:00–14:00 at 2-h intervals (33.5–37.2 °C) on a hot summer day in a field in Shanghai, China) on water content and levels of water-soluble protein, triglycerides, mannitol, and sorbitol in the adult bodies. The results showed that water content significantly decreased and all other metabolic parameters significantly increased in response to temperature stresses with similar patterns in both the laboratory and field, although the respective threshold temperatures were different under the two conditions. The close linkage observed in the two conditions suggests that a short period of heat stress induces water loss and accumulation of thermal metabolites in C. ciliata adults. This heat-resistance provides a defense mechanism counteracting thermal damage in C. ciliata.     

Weatherability of a steam-rolled oat groat chlorophacinone ground squirrel bait under field and laboratory conditions

Investigations of the weatherability of spot-baiting for ground squirrel control in northern CA field studies were conducted with a registered bait consisting of 0.01% chlorophacinone (an anticoagulant rodenticide) on steam-rolled oat groats. For reference purposes, a laboratory test was later conducted in an environmental chamber simulating some of the observed weather conditions. Three weathering plots were established in alfalfa for field tests. Each was baited with rodenticide fortified bait that was handled the same as for a simultaneous control project. Test areas were protected with wire mesh to prevent bait consumption by birds and mammals. Bait samples were collected daily over 7 days, then frozen, and shipped for analysis. Test No. 1 conducted under wet conditions showed a 71% loss of chlorophacinone after 1 week. Test No. 2 demonstrated a 57% loss of chlorophacinone under drier conditions. Test No. 3, a 24 h test under very wet conditions within the alfalfa field irrigated by overhead sprinklers, had a 92% loss of chlorophacinone. Laboratory studies using controlled environmental conditions: light (16 h light:8 h dark), with a mean relative humidity of 98%, and a range of temperature 11.1–27.8°C (52–82°F) showed ≈50% loss of the chlorophacinone. The magnitude was less (37% at 7 days) in the environmental chamber when corrected for water weight gain.     

Nitrogen storage and remobilization in ash (Fraxinus excelsior) under field and laboratory conditions

 Storage and remobilization of nitrogen (N) were studied in ash trees (Fraxinus excelsior) under both field and greenhouse conditions. Experiments in the greenhouse providing ¹⁵N labelled fertilizer to the trees showed that the major quantity of N remobilized during subsequent spring was from the roots, and only a small amount from the stem. This corresponded with a loss of soluble N (proteins and low-molecular-weight compounds) from both roots and stem. On the two field sites, which differed in water availability, there was a decrease in bark N content during leaf growth, but on the dry site net N export from the bark was sustained throughout the whole vegetation period. Remobilized N was derived from soluble proteins and low-molecular-weight compounds on the moist site, which was demonstrated by the seasonal dynamics of a 56 kDa polypeptide in bark and wood. On the dry site, lower contents of soluble proteins were associated with smaller amounts of N remobilized compared to the moist site. Uptake studies of ¹⁵N labelled fertilizer indicated a higher contribution of current uptake to leaf N increment during spring at the dry site compared to the moist site. Differential N availability during the season had a decisive effect on the nitrogen storage dynamics at the two sites. Thus the influence of current N supply on N remobilization and storage as found in the greenhouse-grown plants could be verified under field conditions. Received: 28 July 1995 / Accepted: 17 July 1996     

Some observations on the behaviour of the Recent brachiopod Megerlina pisum under laboratory conditions

Tank experiments with the terebratuloid Megerlina pisum indicate that food is obtained by filtration of sea-water drawn into the shell at the sides and exhaled anteriorly. Under laboratory conditions feeding periods of up to 12 hours were interspersed with resting periods of about equal duration. During the feeding periods the valves were maintained at full gape except for brief interruptions by complete or partial closures. Complete closures lasted several minutes whereas partial closures occurred about half as frequently and lasted only 1 or 2 seconds. Most of these closures did not involve the expulsion of faecal pellets. During the resting periods the valves remained closed for several hours at a time and this condition occasionally continued for 10 hours or more. Apparently a very low respiratory rate operates during these resting periods.     

Proteins under extreme physical conditions

Life on earth is ubiquitous within the limits from -5 to 110 degrees C for temperature, 0.1 to 120 MPa for hydrostatic pressure, 1.0 to 0.6 for water activity and pH 1 to 12. In general, mutative adaptation of proteins to changing environmental conditions tends to maintain 'corresponding states' regarding overall topology, flexibility and hydration. Due to the minute changes in the free energy of stabilization responsible for enhanced stability, nature provides a wide variety of different adaptative strategies. In the case of thermophilic proteins, improved packing densities are crucial. In halophilic proteins, decreased hydrophobicity and clustered surface charges serve to increase water and salt binding required for solubilization at high salt concentration. In the case of barophiles, high-pressure adaptation is expected to be less important than adaptation to low temperatures governing the deep sea. Nothing is known with respect to the mechanisms underlying psychrophilic and acidophilic/alkalophilic adaptation.