Evidence for a correlation between swimming velocity and membrane fluidity of Tetrahymena cells

The influence of the physical state of the membrane on the swimming behaviour of Tetrahymena pyriformis was studied in cells with lipid-modified membranes. When the growth temperature of Tetrahymena cells was increased from 15°C to 34°C or decreased from 39°C to 15°C, their swimming velocity changed gradually in a similar to the adaptive change in membrane lipid composition. Therefore, such adaptive changes in swimming velocity were not observed during short exposures to a different environment. Tetrahymena cells adapted to 34°C swam at 570 μm/s. On incubation at 15°C these cells swam at 100 μm/s. When the temperature was increased to 34°C after a 90-min incubation at 15°C, the initial velocity was immediately recovered. On replacement of tetrahymanol with ergosterol, the swimming velocity of 34°C-grown cells decreased to 210 μm/s, and the cells ceased to move when the temperature was decreased to 15°C. To investigate the influence of the physical state of the membrane on the swimming velocity, total phospholipids were prepared from Tetrahymena cells grown under these different conditions. The fluidities of liposomes of these phospholipid were measured using stearate spin probe. The membrane fluidity of the cells cooled to 15°C increased gradually during incubation at 15°C. On the other hand, the fluidity of the heated cell decreased during incubation at 34°C. Replacement of tetrahymanol with ergosterol decreased the membrane fluidity markedly. Consequently, a good correlation was observed between swimming velocity and membrane fluidity; as the membrane fluidity increased, the swimming velocity increased linearly up to 600 μm/s. These results provide evidence for the regulation of the swimming behaviour by physical properties of the membrane.     

Single crystals of dextran: High temperature polymorph

Lamellar single crystals of a high temperature polymorph of synthetic dextran were prepared at temperatures ranging from 120 to 200°C in a mixture of water and polyethylene glycol. Individual crystals with lath-like shapes gave well resolved electron diffraction diagrams from which the reciprocal unit cell parameters a^*, b^* and γ^* could be measured. The direct cell parameters were then determined from a series of electron diffraction diagrams obtained by sequential tilting of the crystal about the b^* axis. This gave a = 0·922 ± 0·001 nm, b = 0·922 ± 0·001 nm, c (chain axis) = 0·78 ± 0·01 nm, α = γ = 90° and β = 91·3° ± 0·5°. The crystal symmetry was P2₁ with b as the unique monoclinic axis. These data coupled with the observed density of the crystals, indicated that the unit cell contained two antiparallel dextran chains of two residues each. When the crystals were grown at temperatures between 90 and 120°C, a percentage of crystals containing both low and high temperature polymorphs were obtained. These mixed crystals had most likely grown in syntaxy.     

Bioassay to measure effects of cooling and warming rates and protection by dimethyl sulphoxide on survival of frozen Babesia rodhaini

The percentages of Babesia rodhaini parasites that survived different rates of cooling to −79 °C were determined by titrating infectivity in CBA mice before freezing and after thawing. The cryoprotective effect of DMSO and the effect of warming rate were also assessed.When parasitized blood containing 1.5 DMSO was cooled at nominal rates of 2.5 °, 265 °, and 2785 °C/min and warmed at 4320 °C/min, the respective survival rates were 0.075, 4.9, and 0.1%, indicating the existence of an optimal cooling rate. Blood without DMSO cooled and warmed under the same conditions was over 1000 times less infective. When parasitized blood containing DMSO was cooled at 2785 °C/min and warmed at 4320 °, 24.5 °, and 1.84 °C/ min, infectivity decreased progressively with the warming rate. The degrees of haemolysis in frozen and thawed blood indicated that cooling rate was more important than an intact host cell to survival of the parasite.The growth rate of B. rodhaini in CBA mice, estimated to be one binary fission in 8.5 hr, was not affected by the addition of DMSO followed by freezing and thawing.     

Effects of temperature on development, survival, longevity, and fecundity of the Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) predator, Axinoscymnus cardilobus (Coleoptera: Coccinellidae)

Axinoscymnus cardilobus (Homoptera: Aleyrodidae) is an important predator of Bemisia tabaci (Coleoptera: Coccinellidae) that occurs in high population density of B. tabaci. Temperature among other factors is observed to play an important role in the development of arthropods. The effect of temperature on the development of A. cardilobus was studied at seven constant temperature regimes (14, 17, 20, 23, 26, 29, 32 °C). The results indicated that the duration of egg, larval and pupal stages were significantly influenced by increased temperature. The rate of development gradually increased with increase in temperature from 14 °C to 26 °C, but declined from 26 °C to 32 °C. The survival rates of different insect stages were stable at temperatures between 20 °C and 26 °C, but at extreme temperatures of 32 °C and 14 °C, a sharp decrease was evident. Ovipositional period of the female decreased when temperatures were increased from 17 °C to 32 °C. The highest fecundity of the female (225.7 eggs per female) was recorded at 23 °C. Life tables of A. cardilobus were constructed based on the experimental results at temperatures of 14–32 °C. The reproductive rate (R₀), the innate capacity for increase (r_m) and the finite rate of increase (λ) reached the maximum values at 23 °C, of 70.7, 0.059 and 1.062, respectively. The mean generation time (T) decreased with increased temperature from 17 °C to 32 °C, the highest and least values recorded at 17 °C and 32 °C were 112.7 and 38.7, respectively. These results offer valuable insight on the importation and establishment of A. cardilobus into new environments with diverse temperature regimes.     

Isolation of a Derivative ofEscherichia coli–Enterococcus faecalisShuttle Vector pAM401 Temperature Sensitive for Maintenance inE. faecalisand Its Use in Evaluating the Mechanism of pAD1par-Dependent Plasmid Stabilization

A derivative of theEscherichia coli–Enterococcus faecalisshuttle vector pAM401 was isolated by mutagenesis in anE. colimutator strain. This plasmid, designated pAM401ts, was more than an order of magnitude less stable at 38°C than at 30°C in theE. faecalishost strain JH2-2. TheE. faecalisplasmid pAD1-encodedparstability locus was cloned onto pAM401ts, and its effects on plasmid stability and host cell viability were assessed. It was found thatparstabilized pAM401ts at 38°C but also caused a substantial drop in cell viability three to four generations after a temperature shift from 30 to 38°C. After a maximum viability drop of 94%, culture growth recovered as plasmid-free cells began to accumulate. Provision of excess RNAII, the putativeparantidote,in transattenuated cell killing. These characteristics support a postsegregational killing mechanism forpar-mediated plasmid stabilization.     

Differences in the Transbilayer and Lateral Motions of Fluorescent Analogs of Phosphatidylcholine and Phosphatidylethanolamine in the Apical Plasma Membrane of Bovine Aortic Endothelial Cells

In the plasma membrane of various eucaryotic cell types, in particular blood platelets and erythrocytes, it is known that phospholipids are asymmetrically distributed between the two leaflets of the lipid bilayer and that this transverse asymmetry is controlled by an aminophospholipid translocase activity. In this respect, it was of interest to check whether there are differential transbilayer movements between amino- and neutral phospholipids in the apical plasma membrane of vascular endothelial cells which form the inner nonthrombogenic lining of the large blood vessel. In the first step we compared the transbilayer localization and also the rate of lateral motion of two fluorescent analogs of phosphatidylcholine and phosphatidylethanolamine, namely C6-NBD-PC and C6-NBD-PE, inserted into the apical plasma membrane of bovine aortic endothelial cells, in vitro. By the use of back-exchange experiments we have found that C6-NBD-PC could be removed from the cell membrane toward the culture medium regardless of the incubation conditions used, i.e., just after cell labeling at 0°C or even after further cell incubation for 1 h at 0 or 20°C. In contrast, C6-NBD-PE could be removed only when the cells were maintained at 0°C. After incubation for 1 h at 20°C, 85% of the probe molecules remained nonexchangeable, indicating probe translocation from the outer to the inner leaflet of the lipid bilayer. This "flip" process, which occurred at 20°C, was abolished when the endothelial cells were preincubated with N-ethylmaleimide, diamide, vanadate (VO^3-₄) and vanadyl (VO²⁺) ions, a set of substances which inhibit aminophospholipid translocase activity in various systems, and with a combination of sodium azide and 2-deoxyglucose which led to nearly complete ATP depletion in the cells. Fluorescence recovery after photobleaching experiments were also carried out to specify more precisely the localization and dynamics of the probes in the two leaflets of the plasma membrane lipid bilayer. They produced lateral diffusion coefficients D of 1.2 ± 0.05 × 10^-9 cm²/s for C6-NBD-PC and 2.8 ± 0.3 × 10^-9 cm²/s for C6-NBD-PE, when the two probes were located in the outer leaflet of the plasma membrane, just after cell labeling at 0°C. After cell incubation for one hour at 20°C, i.e., when C6-NBD-PC was still in the outer leaflet whereas C6-NBD-PE was translocated in the inner leaflet, D was observed to slightly increase for C6-NBD-PC (D = 1.9 ± 0.06 × 10^-9 cm²/s) and to greatly increase by at least a factor of 3 for C6-NBD-PE (D = 9.1 ± 0.9 × 10^-9 cm²/s). These results show that the plasma membrane of bovine aortic endothelial cells is equipped with a protein-dependent and energy-mediated phosphatidylethanolamine translocase activity and that the lateral diffusion rate of this phospholipid is much faster in the inner than in the outer leaflet of the lipid bilayer, thus indicating large differences in the fluidity of the two halves of this membrane.     

Effect of Temperature on the Life History of Cirrospilus sp. near lyncus (Hymenoptera: Eulophidae), a Parasitoid of Phyllocnistis citrella (Lepidoptera: Gracillariidae)

The effect of four constant temperatures on the life history of Cirrospilus sp. near lyncus was examined in the laboratory. This species is one of the most abundant generalist indigenous parasitoids of the citrus leafminer, Phyllocnistis citrella Stainton, in Spain. Adult lifespan of C. sp. near lyncus decreased from 50.2 to 9.1 days as temperatures increased from 15 to 30°C, respectively. Both gross fecundity and host-feeding were highest at 20°C (170.48 eggs and 32.33 hosts). Oviposition rates were optimal at higher temperatures (5.22 eggs per day at 25°C and 4.79 eggs per day at 30°C) and were dependent on female age. In contrast, host-feeding rates for a given temperature did not depend on age. Generation time decreased with increasing temperatures from 68.05 days at 15°C to 12.19 days at 30°C. Net reproduction peaked at 20°C (68.86 viable females per female). Intrinsic rate of increase doubled from 15°C (0.059 females per female per day) to 20°C (0.127 females per female per day) and almost doubled again from 20 to 30°C (0.210 females per female per day). Given these parameters, C. sp. near lyncus could perform optimally in the area occupied by P. citrella in the Mediterranean region.     

Heat-sensitive development of the phagocytotic organelle in a Tetrahymena mutant

A laboratory-induced mutant with heat-sensitive development of the phagocytotic organelle has been isolated in Tetrahymena pyriformis, syngen 1; the mutant cells form food vacuoles at 30 °C, but not after incubation at 37 °C. Mutant cells transferred to 37 °C undergo a maximum of 3–5 doublings, but a sizeable fraction remains viable for several days. Results of temperature shift-up experiments reveal that an oral apparatus (OA) constructed at 30 °C remains functional at 37 °C, while one constructed at 37 °C is non-functional with regard to phagocytosis. Preliminary cytological observations reveal severe structural abnormalities of the OA. Thus the mutant appears to be primarily affected in the morphogenesis of the OA. The phenotypic effect of the mutation is reversible by a temperature shiftdown. Changes in phenotype caused by temperature shifts in either direction can occur even in stationary or starved cultures. Cell division is not required for the resumption of phagocytosis after a temperature shiftdown. Null-formers obtained at the first doubling after a temperature shift-up can divide at least once more, indicating that a functional OA is not required for cell division at any stage of the cell cycle. Mutants defective in phagocytosis may prove useful in gaining deeper understanding of this mechanism and its relationship to other cellular processes.     

A temperature-sensitive N-glycosylation mutant of S. cerevisiae that behaves like a cell-cycle mutant

The temperature-sensitive S. cerevisiae mutant alg1-1, defective in the N-glycosylation of proteins, shows a first cycle arrest at the non-permissive temperature of 36 °C. The cell number increases by 50% and the absorbance approximately doubles. The budding index of 0.4 at 26 °C drops to 0.15 and DNA synthesis quickly comes to a halt at 36 °C. When the temperature is lowered again, budding and DNA synthesis start after a lag of 2–3 h; α-factor prevents both these processes in cells of mating type a. In addition, cells arrested at 26 °C in G1 with α-factor also do not start budding at the non-permissive temperature after removal of α-factor. The results support recent findings obtained with tunicamycin and suggest that at least one glycoprotein is required for G1-S phase transition in yeast.     

NMR studies of glycerol permeability in lipid vesicles, erythrocytes and the alga Dunaliella

Glycerol diffusional permeabilities through the cytoplasmic cell membrane of Dunaliella salina, the cell envelope of pig erythrocyte and egg phosphattidylcholine vesicles were measured by NMR spectroscopy employing the spin-echo method and nuclear T₁ relaxation. The following permeability coefficients (P) and corresponding enthalpies of activation (ΔH^‡) were determined for glycerol at 25°C: for phosphatidylcholine vesicles 5·10⁻⁶ cm/s and 11±2 kcal/mol; for pig erythrocytes 7·10⁻⁸ cm/s and 18±3 kcal/mol, respectively; for the cytoplasmic membrane of D. salina the permeability at 17°C was found to be exceptionally low and only a lower limit (P<5·10⁻¹¹cm/s) could be calculated. At temperatures above 50°C a change in membrane permeability occurred leading to rapid leakage of glycerol accompanied by cell death. The data reinforce the notion that the cytoplasmic membrane of Dunaliella represents a genuine anomaly in its exceptional low permeability to glycerol.     

In vitro studies of the effect of Environmental Conditions on the anthacnose pathogen of bananas, Colletotrichum musae

In vitro studies were undertaken to determine the effect of pH, temperature, water availability and carbon dioxide (CO₂) concentration on germination and growth of Colletotrichum musae, the causal pathogen of anthracnose of bananas. The optimum pH for germination and growth varied between 4·0 and 5·0 depending on temperature. At low pH (< 3·0) and 15°C, both germination and growth were significantly reduced, with a marked increase in the lag time, in days, prior to growth. C. musae germinated and grew over a wide range of water activities (a_w; 0·995−0·94 and 0·995−0·92, respectively) at 20, 25 and 30°C. In all cases where germination occurred appresoria were subsequently produced. Optimum growth occurred at 30°C and 0·995 a_w, although this changed to 0·98 a_w at 35°C. Increasing CO₂ concentration to 15% or reducing oxygen concentration to 1% resulted in a significant (P < 0·05) reduction in growth, but did not inhibit growth completely.     

Rate of DNA synthesis as a function of temperature in cultured hamster fibroblasts (V-79) and HeLa-S3 cells

The rates of intracellular DNA synthesis at various temperatures between 39 ° and 31 °C were determined in hamster fibroblasts and HeLa cells by measuring average amounts of ³H-thymidine incorporated per cell in S phase per unit of time. The energy of activation and Q₁₀ for intracellular DNA synthesis were calculated from the slopes of the relative rates of DNA synthesis in HeLa cells and hamster fibroblasts vs. time, plotted on Arrhenius coordinates. In both cell types the incorporation of thymidine into DNA is characterized by an energy of activation of 21 000 calories/mole and a Q₁₀ of 2.94. The absolute rates of DNA synthesis were determined in hamster cells at various temperatures, with values ranging from 1.44 to 0.60 × 10⁻¹⁴ g DNA/ min/cell at 39 ° to 31 °C, respectively. The length of the S phase of the hamster cell was calculated over a 39 ° to 31 °C range, and found to be 5.0 to 11.9 h, respectively. It is concluded that the S phase length is partly determined by the rate of temperature-dependent DNA synthesis.     

Characterization of inducible cold-active β-glucosidases from the psychrotolerant bacterium Shewanella sp. G5 isolated from a sub-Antarctic ecosystem

The psychrotolerant bacterium Shewanella sp. G5 was used to study differential protein expression on glucose and cellobiose as carbon sources in cold-adapted conditions. This strain was able to growth at 4 °C, but reached the maximal specific growth rate at 37 °C, exhibiting similar growing rates values with glucose (μ: 0.4 h⁻¹) and cellobiose (μ: 0.48 h⁻¹). However, it grew at 15 °C approximately in 30 h, with specific growing rates of 0.25 and 0.19 h⁻¹ for cellobiose and glucose, respectively. Thus, this temperature was used to provide conditions related to the environment where the organism was originally isolated, the intestinal content of Munida subrrugosa in the Beagle Channel, Fire Land, Argentina. Cellobiose was reported as a carbon source more frequently available in marine environments close to shore, and its degradation requires the enzyme β-glucosidase. Therefore, this enzymatic activity was used as a marker of cellobiose catabolism. Zymogram analysis showed the presence of cold-adapted β-glucosidase activity bands in the cell wall as well as in the cytoplasm cell fractions. Two-dimensional gel electrophoresis of the whole protein pattern of Shewanella sp. G5 revealed 59 and 55 different spots induced by cellobiose and glucose, respectively. Identification of the quantitatively more relevant proteins suggested that different master regulation schemes are involved in response to glucose and cellobiose carbon sources. Both, physiological and proteomic analyses could show that Shewanella sp. G5 re-organizes its metabolism in response to low temperature (15 °C) with significant differences in the presence of these two carbon sources.     

Relationship between temperature optima and secreted protease activities of three Pythium species and pathogenicity toward plant and animal hosts

The in vitro physiological characteristics of three species of Pythium (oomycetes) that utilize different food sources were compared with their ecological activities: P. insidiosum is a pathogen of mammals (including humans), P. graminicola infects the roots of graminaceous hosts, and P. grandisporangium is an enigmatic water mold isolated from mangrove leaves and marine algae. P. insidiosum and P. graminicola showed peak growth rates at 37 °C before complete inhibition of growth at 40 °C; P. grandisporangium grew fastest at 22 °C. Differences between the invasive pressures exerted by the hyphae of these microorganisms were not considered significant in relation to the substrates colonized by these water molds. All three species showed substantial secreted protease activity, producing three or more serine proteases with weights ranging from 24-38 kDa. Fastest growth rates were supported when collagen was supplied as the sole carbon source, and none of the species were able to grow on purified plant cell wall polysaccharides. The growth and nutritional characteristics of P. graminicola and P. grandisporangium bear little obvious relationship to the ecological niches that they inhabit. This highlights the caution necessary in extrapolating from laboratory analyses to the natural environment, and points to the potential importance of ecological opportunity in determining the host range and food source of certain microorganisms.     

Evidence for non-uniform distribution of d-glucose within human red cells during net exit and counterflow

The kinetic parameters of net exit of d-glucose from human red blood cells have been measured after the cells were loaded to 18 mM, 75 mM and 120 mM at 2°C and 75 mM and 120 mM at 20°C. Reducing the temperature, or raising the loading concentration raises the apparent K_m for net exit. Deoxygenation also reduces the K_m for d-glucose exit from red blood cells loaded initially to 120 mM at 20°C from 32.9 ± 2.3 mM (13) with oxygenated blood to 20.5 ± 1.3 mM (17) (P<0.01). Deoxygenation increases the ratio V_max/K_m from 5.29 ± 0.26 min⁻¹ (13) for oxygenated blood to 7.13 ± 0.29 min⁻¹ (17) for deoxygenated blood (P < 0.001). The counterflow of d-glucose from solutions containing 1 mM ¹⁴C-labelled d-glucose was measured at 2°C and 20°C. Reduction in temperature, reduced the maximal level to which labelled d-glucose was accumulated and altered the course of equilibration of the specific activity of intracellular d-glucose from a single exponential to a more complex form. Raising the internal concentration from 18 mM to 90 mM at 2°C also alters the course of equilibration of labelled d-glucose within the cell to a complex form. The apparent asymmetry of the transport system may be estimated from the intracellular concentrations of labelled and unlabelled sugar at the turning point of the counterflow transient. The estimates of asymmetry obtained from this approach indicate that there is no significant asymmetry at 20°C and at 2°C asymmetry is between 3 and 6. This is at least 20-fold less than predicted from the kinetic parameter asymmetries for net exit and entry. None of the above results fit a kinetic scheme in which the asymmetry of the transport system is controlled by intrinsic differences in the kinetic parameters at the inner and outer membrane surface. These results are consistent with a model for sugar transport in which movement between sugar within bound and free intracellular compartments can become the rate-limiting step in controlling net movement into, or out of the cell.     

Effect of temperature on survival, development and reproduction of the predatory lacewing Dichochrysa prasina (Neuroptera: Chrysopidae) reared on Ephestia kuehniella eggs (Lepidoptera: Pyralidae)

Preimaginal development and adult longevity and reproduction of Dichochrysa prasina Burmeister were studied at six constant temperatures (15, 20, 25, 27, 30 and 33 °C) and a photoperiod of 16:8 (L:D). Eggs of the flour moth Ephestia kuehniella (Zeller) were used as food throughout preimaginal development, whereas the adults of D. prasina fed on a liquid diet of water, yeast hydrolysate, sugar and honey. At the highest tested temperature of 33 °C no larvae completed their development. At the rest of the tested temperatures the egg to adult developmental period ranged from approximately 92 days at 15 °C to 25 days at 30 °C. Percentages of adult emergence ranged from 36% at 15 °C to 84% at 30 °C. Both adult longevity and fecundity were significantly affected by temperature and the intrinsic rate of increase (r_m) reached its maximum value at 27 °C. These results could be useful for the establishment of a small scale rearing and mass production of D. prasina.     

The RustPuccinia abruptavar.partheniicola,a Potential Biocontrol Agent of Parthenium Weed: Environmental Requirements for Disease Progress

The rust fungusPuccinia abruptavar.partheniicola,a potential biological control agent of parthenium weed (Parthenium hysterophorus), was evaluated under controlled environmental conditions. A range of spore germination temperatures as well as dew period durations and temperatures were investigated to determine some of the environmental requirements for disease establishment and disease progress. Plants were inoculated with urediniospores and exposed to dew periods between 3 to 12 h at temperatures of 10, 15, or 20°C. For disease expression, the inoculated plants were then grown in a glasshouse at one of two temperature regimes (30/26°C or 18/13°C; day/night). Urediniospores germinated best at 12 ± 1°C, with lower germination rates at 5°C or above 20°C. No infection occurred when the plants were exposed to dew periods of ≤3 h, regardless of the incubation temperature. The disease progressed most rapidly when plants were inoculated and incubated for a dew period of at least 12 h at a temperature of 15 ± 1°C. The disease progressed most slowly following inoculation at dew periods of 6 h or less. Disease progress was more rapid when the plants were exposed to a cool-temperature regime (18/13°C) than when exposed to a warm-temperature regime (30/26°C). This suggests that good infection of parthenium weed could be obtained when the urediniospores arrive on the plants during the afternoon in the cooler months of the central Queensland autumn when relatively long dew periods are expected.     

The Effect of Rearing Temperature on Flight Initiation of Trichogramma sibericum Sorkina at Ambient Temperatures

Trichogramma sibericum Sorkina was reared in the laboratory at three temperatures: 16, 21, and 26°C. Individuals from each of these treatments were then tested for propensity to initiate flight at one of four ambient temperatures: 16, 19, 21, or 26°C. Both rearing and ambient temperatures had significant effects on flight initiation. Insects reared at 16°C had the highest mean proportion of flyers; insects reared at 26°C had the lowest. The proportion of insects initiating flight increased with increasing ambient temperature. Also, the interaction of these two temperature experiences was significant. Insects reared at 16°C were more likely to initiate flight at 16°C than insects reared at 21 or 26°C. These results indicate that performance (as assessed by flight initiation) at ambient temperature is dependent on the temperature previously experienced during rearing.     

Effects of acute temperature or salinity stress on the immune response in sea cucumber, Apostichopus japonicus

Invertebrates are increasingly raised in mariculture, where it is important to monitor immune function and to minimize stresses that could suppress immunity. The activities of phagocytosis, superoxide dismutase (SOD), catalase (CAT), myeloperoxidase (MPO), and lysozyme (LSZ) were measured to evaluate the immune capacities of the sea cucumber, Apostichopus japonicus, to acute temperature changes (from 12 °C to 0 °C, 8 °C, 16 °C, 24 °C, and 32 °C for 72 h) and salinity changes (from 30‰ to 20‰, 25‰, and 35‰ for 72 h) in the laboratory. Phagocytosis was significantly affected by temperature increases in 3 h, and by salinity (25‰ and 35‰) changes in 1 h. SOD activities decreased significantly in 0.5 h to 6 h samples at 24 °C. At 32 °C, SOD activities decreased significantly in 0.5 h and 1 h exposures, and obviously increased for 12 h exposure. CAT activities decreased significantly at 24 °C for 0.5 h exposure, and increased significantly at 32 °C in 3 h to 12 h exposures. Activities of MPO increased significantly at 0 °C in 0.5 h to 6 h exposures and at 8 °C for 1 h. By contrast, activities of MPO decreased significantly in 24 °C and 32 °C treatments. In elevated-temperature treatments, activities of LSZ increased significantly except at 32 °C for 6 h to 12 h exposures. SOD activity was significantly affected by salinity change. CAT activity decreased significantly after only 1 h exposure to salinity of 20‰. Activities of MPO and LSZ showed that A. japonicus tolerates limited salinity stress. High-temperature stress had a much greater effect on the immune capacities of A. japonicus than did low-temperature and salinity stresses.     

Effects of temperature on development of vedalia beetle, Rodolia cardinalis (Mulsant)

The effect of temperature on the development of the vedalia beetle, Rodolia cardinalis (Mulsant) (Coleoptera: Coccinellidae), fed Icerya purchasi Maskell (Homoptera: Margarodidae) under controlled laboratory conditions was studied. Adults exposed to temperatures of 25, 28, 31, 34, and 37 °C for 72 h showed 95–100% survival, however egg production was significantly reduced at 34 and 37 °C. In addition, eggs maintained at 34 °C showed reduced hatch and survival of larvae, and eggs held at 37 °C failed to hatch. The duration of each developmental stage and survival of each stage were measured at 10, 14, 18, 22, and 25 °C. There was no egg eclosion at 10 °C. The developmental time from egg to adult emergence decreased from 79 to 18 days for temperatures from 14 to 25 °C. The sex ratio was unaffected by these temperatures. The lower developmental temperature threshold of R. cardinalis was estimated to be 10.8 °C and the degree–day accumulation was calculated as 279 for development from egg to adult eclosion. These results will guide further research designed to optimize management of vedalia populations in the San Joaquin Valley of California.