Effects of constant and fluctuating temperatures on sporulation and infection by the aphid-pathogenic fungus Pandora neoaphidis

Laboratory studies were performed to assess the importance of temperature on sporulation and infection by the aphid-pathogenic fungus Pandora neoaphidis (Remaudière and Hennebert) Humber. Numbers of primary conidia discharged from mycelium formulated as alginate granules and unformulated mycelial mats were assessed, as well as infection of the potato aphid, Macrosiphum euphorbiae (Thomas) (Homoptera, Hemiptera, Aphididae), using culture plugs as inoculum sources. Sporulation from experiments at constant temperatures indicated the optimum temperature range was 10–20°C for both mycelial preparations and there was no or very little sporulation at 30°C. Infection of aphids kept at 15°C was 34–50%, while infection at 25°C was 11–44%. At 20°C, 77–79% of aphids were infected. Under fluctuating temperature cycles, conidia numbers did not differ when mycelial preparations were maintained at 18–25°C compared with 18–20°C, but fewer conidia were recorded when preparations were exposed continuously to 18–30°C. Infections of inoculated aphids kept for varying numbers of days at 18–25°C varied between 24–47%, but only 3–32% of aphids were infected when exposed to a cycle of 18–30°C for various times. Unformulated mycelial mats of P. neoaphidis appear to be superior to forumlated alginate granules for use in experimental greenhouse and field trials, since temperature stability is similar for both materials but mycelial mats are much easier to produce.     

Diel Movements of Bat Rays, Myliobatis californica, in Tomales Bay, California: Evidence for Behavioral Thermoregulation?

We used ultrasonic telemetry to examine movement patterns of 11 bat rays, Myliobatis californica, in Tomales Bay, California. Tomales Bay is long (20km) and narrow (1.4km), and is hydrographically separated into outer and inner bay regions. The outer bay (the outermost 8km) is characterized by oceanic conditions while the shallow inner bay (the innermost 12km) features wide seasonal temperature shifts. Five rays were tracked monthly from October 1990 to November 1991 and six rays (four of which carried temperature-sensing transmitters) were tracked daily from 30 June to 16 July 1992. Mean bat ray movement rate was 8.84mmin^–1 (range 4.49 to 13.40mmin^–1) and was not significantly affected by size (p=0.592), tidal stage (p=0.610), or time of day (p=0.327). Movement direction was unrelated to tidal stage (p=0.472) but showed a highly significant diel pattern (p<0.001). From 2:50–14:50h, rays moved toward the warmer and shallower inner bay, while from 14:50–2:50h they moved toward the cooler and deeper outer bay. These telemetry data, along with known bat ray foraging patterns and respiratory temperature-sensitivity, argue for behavioral thermoregulation as the primary influence on this movement pattern.     

A Cytogenetic Study of the Leaf Beetle Genus Cyrtonus (Coleoptera, Chrysomelidae)

The chromosomes of ten species of Cyrtonus and the genome sizes of six are surveyed. Among the total of 15 chromosomally studied species, 11 have 2n=28 chromosomes and a 13+Xy_p male meioformula, three have 2n=40 and 19+Xy_p and one 2n=46 and 22+Xy_p. All but one species with 28 chromosomes show only metacentric or submetacentric chromosomes, whereas the species with 40 and 46 chromosomes display some telocentrics or subtelocentrics, that are probably derived from the former by centric fissions. However, since the number of major chromosome arms is strikingly higher in these latter species (NF=70 and 78) than in the 28-chromosome species (mostly NF=56), other chromosomal rearrangements such as pericentric inversions or heterochromatin accretions could also be involved. The genome sizes display a narrow range, from 1C=0.6–1.22pg, and they are not significantly correlated with the chromosome numbers. Some possible factors implied in the rough chromosomal evolution of Cyrtonus are discussed in relation to a few other genera of the subfamily Chrysomelinae.     

Optimization of cryopreservation of Artemisia annua L. callus

Cryopreservation of callus tissue of Artimisia annua L. was optimized. Two lines of calli were precultured on MS medium with 5% (v/v) dimethyl sulfoxide, and protected by a cryoprotectant containing 15% (v/v) ethylene glycol, 15% (v/v) dimethyl sulfoxide, 30% (v/v) glycerol and 13.6% (w/v) sucrose. The highest survival rate of callus A201 reached 87% after it was pretreated at 25°C, cryopreserved by liquid nitrogen, recovered in water bath at 25°C and reloaded at 25°C with 34% (w/v) sucrose solution, and that of callus A202 reached 78% after it was treated as callus A201, except pretreated at 35°C, recovered at 35°C and reloaded with 47.8% (w/v) sucrose solution.     

The temperature-dependent duration of development and parasitism of three cereal aphid parasitoids, Aphidius ervi, A. rhopalosiphi, and Praon volucre

Temperature dependencies were established for the egg-to-mummy and mummy-to-adult phases, for mummy mortality, and for parasitism of Aphidius ervi Haliday, Aphidius rhopalosiphi De Stefani-Perez, and Praon volucre (Haliday) (Hymenoptera, Aphidiidae), three parasitoids of Sitobion avenae (Fabricius) (Homoptera, Aphididae), at 8°C, 12°C, 16°C, 20°C, and 25°C on winter wheat (cv. Haven). A physiological model described temperature-dependent development over the full temperature range, whereas a linear model was fitted for data above 8°C and used to estimate the lower temperature thresholds and day-degrees (° D) required for development. The thresholds for A. ervi were 2.2°C for egg-mummy development and 6.6°C for mummy-adult development, those for A. rhopalosiphi were 4.5°C and 7.2°C, and those for P. volucre were 3.8°C and 5.5°C. The time to develop into mummies and adults differed significantly between the three species: A. ervi development into mummies required an average of 159 ° D, while development into adults took an average of 73 ° D. The corresponding average times required for A. rhopalosiphi and P. volucre to develop mummies were 124° D and 126° D, while their development into adults required an average of 70° D and 150° D, respectively. Mummy mortality was 25–35% at 8°C and less at the higher temperatures tested, but began to increase again at 25°C, showing a quadratic relationship between mortality and temperature. Parasitization was very low or, in the case of P. volucre, absent up to 12°C and thereafter increased with increasing temperature. The relationship between parasitization, recorded as percent aphids mummified, and temperature was linear at the temperatures tested and depended on species. A. ervisuperparasitized 11.1% aphids at 20°C and 16.6% aphids at 25°C, whereas superparasitism was low in A. rhopalosiphi and absent in P. volucre. From 16°C to 25°C the P. volucre sex ratio increased. For A. ervi and A. rhopalosiphi there was no trend with temperature, but at 20°C and 25°C it was close to even. Field data for 1996 and 1997 allowed for a comparison of actual and expected emergence of overwintering mummies. In both years, parasitoids were predicted to have emerged from overwintering mummies well in advance of the onset of aphid infestation, and more than a month earlier than the first parasitized aphids were found in winter wheat. Observations from trap plants in other crops supported the predictions of the models. Other factors that can affect biological control by cereal aphid parasitoids are discussed.     

Early development of the self-fertilizing mangrove killifish <Emphasis Type="Italic">Rivulus marmoratus</Emphasis> reared in the laboratory

The mangrove killifish Rivulus marmoratus was reared at 25°±1°C and 17ppt salinity from 0 to 100 days after hatching (DAH), and its early development was described by examining growth and morphometric parameters, meristic characters (vertebral and fin-ray counts), bone-cartilage development, and pigmentation. Growth was isometric for preanal length, head length, snout length, body depth, pectoral-fin length, dorsal-fin length, anal-fin length, and caudal-peduncle depth. Negative allometric growth was observed in eye diameter and gape size. Meristic counts (mean±SD) for vertebrae (34.2±0.4) and dorsal- (8.6±0.5), anal- (11.4±0.5), and caudal-fin rays (30.2±0.8) were complete at 0 DAH (n=5), whereas pectoral-fin rays and pelvic-fin rays were complete by 30 DAH (14.5±0.4, n=5) and 60 DAH (4.2±0.8, n=5). Full ossification of meristic elements proceeded in the following sequence: vertebrae (by 30 DAH), caudal-, dorsal-, and anal-fin rays (by 60 DAH), pectoral-fin rays (between 60 DAH and 100 DAH), and pelvic-fin rays (by 100 DAH). Both morphological characters and meristic counts indicate that this species can be considered to be a juvenile after 9.8mm in standard length (20 DAH).     

<Emphasis Type="Italic">In vitro</Emphasis> screening of sugarcane to evaluate smut susceptibility

Tissue-cultured plantlets of three sugarcane (Saccharum spp.) cultivars having a known field smut reaction were screened for susceptibility to Ustilago scitaminea H&P Sydow. Plantlets were inoculated with 0.5 l of a suspension of equally mixed quantities of plus and minus mating type sporidia of U. scitaminea at concentrations ranging from 1×10¹ to 1×10⁶ cells. Fungal sori (whips) were produced in cultivar N12 (intermediate) 6weeks following inoculation with 1×10⁵ mixed sporidia and thereafter in cultivar NCo310 (susceptible) but not in cultivar N19 (resistant). Sori bearing teliospores were produced up to 3months following inoculation and incubation at 26°C. No sori were produced at mixed sporidial concentrations lower than 1×10⁵cells. The in vitro soral production in cultivars N19, N12 and NCo310 was 0, 27.5 and 47.5% respectively. Plantlets inoculated with 1×105sporidia of only one mating-type did not produce sori in any of the three cultivars tested. Blind scoring of an unknown sugarcane cultivar by this method corresponded exactly with its field smut rating.     

Defective remethylation of homocysteine is related to decreased synthesis of coenzymes B2 in thyroidectomized rats

Summary. We investigated the influence of hypothyroidism on homocysteine metabolism in rats, focusing on a hypothetical deficient synthesis of FAD by riboflavin kinases. Animals were allocated in control group (n=7), thyroidectomized rats (n=6), rats with diet deficient in vitamin B2, B9, B12, choline and methionine (n=7), thyroidectomized rats with deficient diet (n=9). Homocysteine was decreased in operated rats (2.6±1.01 vs. 4.05±1.0mol/L, P=0.02) and increased in deficient diet rats (29.56±4.52 vs. 4.05±1.0mol/L, P=0.001), when compared to control group. Erythrocyte-Glutathione-Reductase-Activation-Coefficient (index of FAD deficiency) was increased in thyroidectomized or deficient diet rats (P=0.004 for both). Methylenetetrahydrofolate-reductase and methionine-synthase activities were decreased in thyroidectomized rats but not in those subjected to deficient diet. Cystathionine--synthase was increased only in operated rats. Taken together, these results showed a defective re-methylation in surgical hypothyroidism, which was due in part to a defective synthesis of vitamin B2 coenzymes. This defective pathway was overcompensated by the increased Cystathionine--synthase activity.     

Reproduction of the Endangered Killifish Aphanius iberus at Different Salinities

Adult fish of a freshwater population of the Iberian endangered cyprinodontid Aphanius iberus, were induced to reproduce at salinities of 5, 15, 30, 45 and 60ppt. For each salinity five 30l aquaria were used, each one including a male and two females. Maturity and spawning outside the natural season, were obtained at conditions of 22 to 28°C and a photoperiod of 14L:10D. The larvae were fed with rotifers Brachionus plicatilis and Synchaeta cecilia valentina. Experiment lasted 40 days. The first spawning occurred on the 17th day at 45ppt of salinity and the first embryos hatched on the 34th day at 5 and 15ppt salinity. The final average number of larvae per aquarium ranged from 5.2 (45ppt salinity) to 10.8 (15ppt salinity). No significant differences were found between the average values at different salinities (p<0.01).     

Mode of uptake of sterol by Arthrobacter simplex

The mechanism of uptake of water-insoluble -sitosterol by a newly isolated strain of Arthrobacter simplex SS-7 was studied. The production of an extracellular sterol-pseudosolubilizing protein during growth of A. simplex on -sitosterol was demonstrated by isolating the factor from the cell-free supernatant and its subsequent purification by Sephadex G-150 column chromatography. The M _r of the purified sterol-pseudosolubilizing protein determined by SDS–PAGE was 19kDa. The rate of sterol pseudosolubilization (5.2×10^–3g l^–1h^–1) could not adequately account for the rate of sterol uptake (72×10^–3g l^–1h^–1) and the specific growth rate (56×10^–3 h^–1). However in the unfavourable growth condition, when the cells were treated with sodium azide at the level of 30–60% of MIC, the sterol pseudosolubilization accounted for nearly 74% of the total growth containing 96% free cells. Cellular adherence to substrate particles was found to play an active role in the normal growth of the strain on -sitosterol. Unlike sodium acetate-grown cells, whose surface activity was negligible (60mNm^–1), the sterol-grown cells had strong surface activity (40mNm^–1). The high lipid content and long chain fatty acids in the cell-wall of -sitosterol-grown cells probably contribute to the high sterol adherence activity of the cells.     

Thermophilic and mesophilic bacteria in biofilms associated with corrosion in a heat exchanger

Biofilm development on AISI-1020 carbon steel coupons installed at the outlet of a heat exchanger was evaluated at the thirtieth and the sixtieth days of exposure. Water temperature varied between 41 and 60°C. The most probable number technique (MPN) was applied to quantify mesophilic and thermophilic species of aerobic, anaerobic, and sulphate-reducing bacteria (SRB) in planktonic and sessile phases. The results showed predominance of thermophilic aerobic bacteria in both phases, corresponding to 9.5±0.8×10⁶cells/ml in the planktonic phase. In biofilms, maximal aerobic cell concentration, 7.8±0.6×10⁸cells/cm2, was registered at the sixtieth day. An increase in the number of thermophilic anaerobic and SRB with elapsed time was also observed. The results obtained after 60 days were 5.8±0.4×10⁷ and 8.9±0.9×10⁴cells/cm² for anaerobic and sulphate-reducing bacteria, respectively. Scanning electron microscopy showed a varied composition of species in the biofilms and corrosion on the carbon steel surfaces after biofilm removal.     

Flax anther culture: effect of genotype,cold treatment and media

We report on screening of wide range of flax cultivars for androgenic response and on testing of induction conditions for flax (Linum usitatissimum L.) anther culture and plant regeneration. Anthers were cultured on four different media: Mo, N6, MS and N&N supplemented with various combinations of growth regulators. The induction of callus formation from cultured anthers was the highest on N6 (with cultivar PR FGL 77 – 12 %) and N&N media (with cultivar Carolin – 2.8 %), preferentially after cold pretreatment (7days at 8 °C). Shoots were formed on calli derived from the microspores inside the cultured anthers on media N&N and N6 supplemented with 1mgl^–1 zeatin or 1mgl^–1BAP + 1mgl^–1NAA, respectively and elongated on MS medium supplemented with 2mgl^–1 zeatin. The highest number of shoots (120) was observed with cultivar Red Wing. Shoots were rooted on MS medium supplemented with 2mgl^–1IAA. Our experiments resulted in total in 62 % anther response and 155 plants regenerated and transferred into soil.     

Development, survival and reproduction of Euseius finlandicus (Acari: Phytoseiidae) at different constant temperatures

Development, survival and reproduction of Euseius finlandicus Oudemans were studied at seven constant temperatures (15, 20, 25, 27, 30, 32 and 34°C) in the laboratory. Within the temperature range tested, developmental period from egg to adult varied from 148 to 360.5h and 133.7 to 336.5h for females and males, respectively. The lower thermal threshold for immature development for females and males was 8.9 and 6.4°C, respectively. Survival during immature development exceeded 90% at all the temperatures from 15 to 32°C, but at 34°C an abrupt decline was recorded. Female longevity decreased gradually from 82.7d at 15°C to 12.2 d at 34°C. The mean generation time ranged from 44.3d at 15°C to 15.9d at 32°C. The highest r _m value (0.2817) was obtained at 30°C and the lowest at 15°C (0.0976). Temperatures above 30°C had an adverse effect on population increase.     

Fine root biomass,production and turnover in a fertilized <Emphasis Type="Italic">Larix leptolepis</Emphasis> plantation in central Korea

The effects of fertilization [control (C), 200kgNha^–1+25kgP ha^–1 (LNP) and 400kgNha^–1+ 50kgP ha^–1 (HNP)] on fine root dynamics were examined in a 40-year-old Larix leptolepis plantation in central Korea. The average fine root biomass during the growing season for C, LNP and HNP was 957, 934 and 814kgha^–1, respectively, whereas the fine root production for C, LNP and HNP was 2103, 2131 and 2066kgha^–1, respectively. Nitrogen and P inputs into the soil via fine root turnover for C, LNP and HNP were 23.0 and 1.2, 23.3 and 1.2 and 22.6 and 1.2kgha^–1, respectively. There were no significant differences in fine root biomass, production and N and P inputs through fine root turnover between the fertilization treatments during the first growing season after fertilization.     

Laboratory culture studies of Trichodesmium isolated from the Great Barrier Reef Lagoon, Australia

Cultures of Trichodesmium from the Northern and Southern Great Barrier Reef Lagoon (GBRL) have been established in enriched seawater and artificial seawater media. Some cultures have been maintained with active growth for over 6years. Actively growing cultures in an artificial seawater medium containing organic phosphorus (glycerophosphate) as the principal source of phosphorus have also been established. Key factors that contributed to the successful establishment of cultures were firstly, the seed samples were collected from depth, secondly, samples were thoroughly washed and thirdly, incubations were conducted under relatively low light intensities (PAR 40–50molquantam^–2s^–1). N₂ fixation rates of the cultured Trichodesmium were found to be similar to those measured in the GBRL. Specific growth rates of the cultures during the exponential growth phase in all enriched media were in the range 0.2–0.3day^–1 and growth during this phase was characterised by individual trichomes (filaments) or small aggregations of two to three trichomes. Characteristic bundle formation tended to occur following the exponential growth phase, which suggests that the bundle formation was induced by a lack of a necessary nutrient e.g. Fe. Results from some exploratory studies showed that filament-dominated cultures of Trichodesmium grew over a range of relatively low irradiances (PAR 5–120molquantam^–2s^–1) with the maximum growth occurring at 40–50molquantam^–2s^–1. These results suggest that filaments of the tested strain are well adapted for growth at depth in marine waters. Other studies showed that growth yields were dependent on salinity, with maximum growth occurring between 30 and 37psu. Also the cell yields decreased by an order of magnitude with the reduction of Fe additions from 450 to 45nM. No active growth was observed with the 4.5nM Fe addition.     

An alkalophilic thermostable lipase produced by a new isolate of Bacillus alcalophilus

An extremophilic bacterium, isolated from mangrove detritus, produced an extracellular alkaline-thermostable lipase. The bacterium was identified on the basis of cell morphology, growth characteristics, G+C molar ratio and DNA/DNA hybridization as a strain of Bacillus alcalophilus. The bacterium grew optimally at pH 10.6, 60°C with NaCl tolerance up to 7.5% (w/v). Carbonates and/or bicarbonates enhanced lipase production, while NaCl had an inhibitory effect. Maximum lipase activity was at 60°C at pH 10.6, with approx. 60% of its activity being retained at 80°C after 20min and 80% of its activity was retained at pH 11 after incubation at 60°C. A partially purified lipase had similar stabilities to the crude enzyme.     

Increased thermal stability of glucose dehydrogenase by cross-linking chemical modification

A hetero-oligomeric glucose dehydrogenase (GDH) from a moderate thermophilic bacterium, SM4 was cross-linked with glutaraldehyde (GA) and it now showed only one optimum temperature for reaction at around 65°C, which approximately follows the Arrhenius equation. The native enzyme had shown optima at both 45°C and 75°C. In addition to the alteration of the optimum temperature for reaction, GA cross-linked GDH retained more than 90% of its initial activity even after 30 min of incubation at 65°C.     

Purification and characterization of aspartate aminotransferase from developing embryos of the camel tick Hyalomma dromedarii

Aspartate transaminase (AST) activity in the camel tick Hyalomma dromedarii was followed throughout embryogenesis. During purification of AST to homogeneity, ion exchange chromatography lead to four separate forms (termed I, II, III and IV). AST II with the highest specific activity was pure after chromatography on Sephacryl S-300. The molecular mass of AST II was 52KDa for the native enzyme, composed of one subunit of 50KDa. AST II had a Km value of 0.67mM for -ketoglutarate and 15.1mM for aspartate. AST II had a pH optimum of 7.5 with heat stability up to 50°C for 15min. The enzyme was activated by MnCl₂, and inhibited by CaCl₂, MgCl₂, NiCl₂, and ZnCl₂.     

Continuous isomerization of D-fructose to D-mannose by immobilized Agrobacterium radiobacter cells

d-Fructose was isomerized to d-mannose using immobilized Agrobacterium radiobacter that produces a thermostable mannose isomerase. The cells were immobilized by adsorption on chitosan or by glutaraldehyde crosslinking in the presence of albumin. Optimum conditions for mannose isomerase activity were 60°C and pH 7.5. Continuous reaction at 55°C was achieved with immobilized cells packed in a column to produce d-mannose.     

Uptake of sewage derived nitrogen by<Emphasis Type="Italic"> Ulva rigida</Emphasis> (Chlorophyceae) in Bahía Nueva (Golfo Nuevo,Patagonia, Argentine)

Uptake kinetics of nitrogen derived from sewage–seawater mixtures (2.5–20% v/v effluent) were determined in the laboratory for Ulva rigida (Chlorophyceae) native from Bahía Nueva (Golfo Nuevo, Patagonia, Argentine). In terms of nitrogen concentration, experimental enrichment levels varied between 53.7 and 362.3M of ammonium and between 0.77 and 6.21M of nitrate+nitrite. Uptake rates were fitted to the Michaelis–Menten equation, with the following kinetic parameters: ammonium: V_max = 591.2molg^–1h^–1, K _s=262.3M, nitrate+nitrite: V _max=12.9molg^–1h^–1, K _s=3.5M). Both nutrients were taken up simultaneously, but ammonium incorporation was faster in all cases. The results show a high capability of Ulva rigida to remove sewage-derived nitrogen from culture media. In the field, most of the nitrogen provided by the effluent would be tied up in algal biomass, supporting low nitrogen levels found at a short distance away from the source.