Study of protective role of the polysaccharide-containing components of capsules of Azospirillum brasilense

The involvement of the carbohydrate components of the Azospirillum brasilense Sp245 capsules in bacterial protection from the action of extreme factors was investigated. The survival of encapsulated and non-encapsulated azospirilla exposed to elevated (46-48 degrees C) and below-freezing (-20 and -70 degrees C) temperatures, extreme pH values (2 and 10), and to drying was studied. High-molecular-weight carbohydrate-containing complexes (lipopolysaccharide-protein complex and polysaccharide-lipid complex) were isolated from the capsular material of azospirilla. It was shown that the addition of these complexes to the suspension of decapsulated cells before exposing them to extreme factors enhanced their survival rates by 15 to 51%.     

Pigment–Protein Complexes and the Number of Reaction Centers of the Photosystems in Pea Chlorophyll Mutants

We studied fluorescent and absorption properties of the chloroplasts and pigment–protein complexes isolated by gel electrophoresis from the leaves of pea, the parent cultivar Torsdag and mutants chlorotica 2004 and 2014. Specific fluorescence peaks of chlorophyll forms in individual complexes have been determined from the absorption and fluorescence spectra of the chloroplast chlorophyll and their second derivatives at 23 and –196°C. The mutant chlorotica 2004 proved to have an increased intensity of a long-wave band of the light-harvesting complex I at both 23°C (745 nm) and –196°C (728 nm). At the same time, this mutant manifested a decreased accumulation of the chlorophyll forms making up the nearest-neighbor antenna of the PS I reaction center (at 690, 697, and 708 nm). No spectral differences have been revealed between chlorotica 2014 mutant and the parent cultivar. Gel electrophoresis revealed the synthesis of all chlorophyll–protein complexes in both mutants. At the same time, analysis of photochemical activity of PS I and PS II reaction centers and calculations of their number and the size of the light-harvesting antenna have shown that the number of reaction centers in the PS I of chlorotica 2004 mutant is reduced by a factor of 1.7 because its chlorophyll a–protein complex is disturbed by the mutation. The primary effect of chlorotica 2014 mutation remains unclear. The proportional changes in the content of photosystem complexes in this mutant suggest that they are secondary and result from a 50% decrease in chlorophyll content.     

Freeze or dehydrate: only two options for the survival of subzero temperatures in the arctic enchytraeid<Emphasis Type="Italic"> Fridericia ratzeli</Emphasis>

Hygrophilic soil animals, like enchytraeids, overwintering in frozen soil are unlikely to base their cold tolerance on supercooling of body fluids. It seems more likely that they will either freeze due to inoculative freezing, or dehydrate and adjust their body fluid melting point to ambient temperature as has been shown for earthworm cocoons and Collembola. In the present study we tested this hypothesis by exposing field-collected adult Fridericia ratzeli from Disko, West Greenland, to freezing temperatures under various moisture regimes. When cooled at –1 °C min^–1 under dry conditions F. ratzeli had a mean temperature of crystallisation (T_c) of –5.8 °C. However, when exposed to temperatures above standard T_c for 22 h, at –4 °C, most individuals (90%, n= 30) remained unfrozen. Slow cooling from –1 °C to –6 °C in vials where the air was in equilibrium with the vapour pressure of ice resulted in freezing in about 65% of the individuals. These individuals maintained a normal body water content of 2.7–3.0 mg mg^–1 dry weight and had body fluid melting points of about –0.5 °C with little or no change due to freezing. About 35% of the individuals dehydrated drastically to below 1.1 mg mg^–1 dry weight at –6 °C, and consequently had lowered their body fluid melting point to ca. –6 °C at this time. Survival was high in both frozen and dehydrated animals at –6 °C, about 60%. Approximately 25% of the animals (both frozen and dehydrated individuals) had elevated glucose concentrations, but the mean glucose concentration was not increased to any great extent in any group due to cold exposure. The desiccating potential of ice was simulated using aqueous NaCl solutions at 0 °C. Water loss and survival in this experiment were in good agreement with results from freezing experiments. The influence of soil moisture on survival and tendency to dehydrate was also evaluated. However, soil moisture ranging between 0.74 g g^–1 and 1.15 g g^–1 dry soil did not result in any significant differences in survival or frequency of dehydrated animals even though the apparent wetness and structure of the soil was clearly different in these moisture contents.Abbreviations DW dry weight - FW fresh weight - MP melting point - RH relative humidity - Tc crystallisation temperatures - WC water contentCommunicated by I.D. Hume     

Freeze-preservation of buds from Scots pine trees

A procedure has been developed for freeze-preservation of buds of the Scots pine (Pinus sylvestris L.). Instead of liquid nitrogen, cold storage in –80°C was used. The partly dormant material used in the experiments was obtained directly from a natural stand in Northern Finland and no prefreezing or cryoprotectants for preconditioning were used. Cooling velocity was 1°C/min up to a terminal freezing temperature of –39°C, after which the buds were immersed in liquid nitrogen at –196°C for 10 minutes. The material was then transferred to a deepfreezer at –80°C and stored up to 6 months. After rapid thawing, the buds were sterilized and their viability was tested by FDA staining and by culturing meristems on 1/2 MS medium for at least two weeks. All the freezing experiments were performed during March and April. The best survival of buds (90–100%) was achieved at the beginning of April, after which a pronounced decline in survival occurred obviously due to a rise in the water content of the buds.     

Effects of temperature and salinity on survival of toxigenicVibrio cholerae O1 in seawater

In 1991 and 1992, the Latin American epidemic strain of Vibrio cholerae O1 was isolated from ballast water, bilge water, and sewage taken from cargo ships docked in Mobile Bay, Alabama. The findings raised questions regarding the organism's ability to survive long-term aboard ships and to withstand the exchange of ballast at sea. The effects of temperature (6, 18, and 30°C) and salinity (8, 16, and 32 ppt) on survival of V. cholerae O1 strains C6706 and C6707 and a ballast water isolate in sterile seawater were determined. The ballast water isolate, which had a D-value (number of days required to produce a 1 log₁₀ reduction in colony-forming units per milliliter) of 240 days at 18°C, 32 ppt salinity, had the longest survival time. The range of D-values was 36–240 days at 18°C, 60–120 days at 30°C, and 5–20 days at 6°C. In sterile seawater short-term survival was temperature dependent, whereas long-term survival was salinity dependent. In raw seawater, survival time of the ballast water isolate was reduced to 12–27 days, implying the existence of biological influences. As also shown in our previous work, the organism appeared to be able to survive for several months under relatively stable conditions in ballast water aboard ships; however, viability may be reduced to only a few weeks after the organism is introduced into estuarine or marine environments. Correspondence to: Susan A. McCarthy.     

Survival of sub-zero temperatures by two South Georgian beetles (Coleoptera,Perimylopidae)

Summary The ability of adults and larvae of two species of perimylopid beetles (Hydromedion sparsutum, Perimylops antarcticus) to survive sub-zero temperatures was studied at Husvik, South Georgia in summer during October–December 1990. Experiments determined their survival at constant sub-zero temperatures, their lower lethal temperatures and individual supercooling points. The effects of cooling rates (0.015°, 0.5° and 2.0°C min^–1) and starvation on survival were also assessed. Mean supercooling points of field-collected individuals of both species were in the range -3.0° to -5.4°C with Perimylops having a deeper capacity (ca. 1.5°C) for supercooling relative to Hydromedion. The former species also survived freezing temperatures significantly better than the latter and its mean lower lethal temperature was 2.5°C lower. At a constant temperature of -8.5°C, the median survival times for Perimylops adults and larvae were 19 and 26 h respectively, whilst both stages of Hydromedion died within 3 h. The three cooling rates resulted in significantly different median survival temperatures for adult Hydromedion with 0.5°C min^–1 producing maximum survival. Prior starvation did not have a significant influence on the survival of either species at sub-zero temperatures although both adults survived less well. The results support field observations on the habitats and distribution of these insects, and suggest differing degrees of freezing tolerance.     

Cold hardiness and winter survival of the grape berry moth, Endopiza viteana, in New York State

Laboratory and field investigations were undertaken to evaluate the effect of winter mortality on subsequent infestation levels of the grape berry moth (GBM), Endopiza viteana (Clemens) (Lepidoptera: Tortricidae). Supercooling points (SCP) were used as a measure of the minimum survivable temperature for GBM pupae. The SCP of winter forms (diapausing) from a laboratory colony averaged –25.2 °C in December, –24.3 °C in March, and –24.0 °C in April. When diapausing pupae from a laboratory colony were placed in the field from December to March, the SCP averaged –23.3 °C. The SCP of summer forms from a laboratory colony averaged –21.6 °C in March. Significant levels of mortality (ca. 80%) of diapausing GBM pupae were observed after 24 h at –21 °C. Comparable mortality occurred after 1-week at –15 °C. Eighty-four percent of diapausing pupae survived for 8-months at 3 °C; non diapausing pupae suffered high levels of mortality (ca. 60%) after only 7-days at 3 °C. Field survival of diapausing pupae were significantly greater at soil level than 1-meter above the soil. Pupal survival was greater at 75% r.h. than at 0% or ambient r.h.. In 1986–1987 and 1987–1988, pupae covered with snow or leaf-litter had higher of survival than exposed pupae although these differences were only statistically significant in 1986–1987. The above findings are discussed within the context of potential implications to management strategies for GBM.

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Zusammenfassung Labor und Freilandversuche wurden unternommen um den potenziellen Einfluss von Wintersterben auf subsequenten Wurmbefall des nordamerikanischen Traubenwicklers Endopiza viteana (Clemens) (Lepidoptera: Tortricidae) auszuwerten. Die niedrigste Temperatur wobei Puppen ueberleben konnten ist durch Ueberkuehlungstemperaturen der Puppen gemessen worden. Fuer das ueberwinternde Stadium (in Diapause) einer Laborkolonie lag diese Temperatur durchschnittlich bei minus 25.2 °C in Dezember, minus 24.3 °C in Maerz, und minus 24.0 °C in April. Der Ueberkuehlungspunkt lag um minus 23.3 °C im Durchschnitt fuer Laborkolonie Puppen die waehrend der Diapause von Dezember bis Maerz im Freiland ausgesetzt wurden. Der Ueberkuehlungspunkt von Sommerstadien von der gleichen Kolonie lag im Vergleich um minus 21.6 °C im Maerz. Signifikante Sterblichkeit (um 80%) der Traubenwicklerpuppen wurde bemerkt nach 24 Stunden bei minus 21 °C. Vergleichbar war die Sterblichkeit nach einer Woche bei minus 15 °C. Nach 8 Monaten bei 3 °C ueberlebten 84% der Puppen in Diapause; 60% der Puppen nicht in Diapause starben nach 7 Tage bei 3 °C. Das Ueberlebensprozent diapausierender Puppen im Freien war signifikant hoeher auf der Erdoberflaeche als fuer die 1 m ueber der Oberflaeche. Mehr Puppen ueberlebten bei 75% relativer Luftfeuchtigkeit als bei 0% oder umgebender Luftfeuchtigkeit. In 1986–1987 und 1987–1988 Puppen die mit Schnee oder Laub bedeckt waren, ueberlebten prozentual mehr als die ohne jedes Bedeckungsmaterial. Die Ergebnisse werden im Kontext ihrer potenzieller Verwendung fuer Kontrolle des Traubenwicklers diskutiert.

     

Stability of Glucose 6-Phosphate Dehydrogenase Complexed with Its Substrate or Cofactor in Aqueous and Micellar Environment

Inactivation of glucose 6-phosphate dehydrogenase (G6PDH) complexed with its substrate, glucose 6-phosphate (GP), or cofactor, NADP⁺, has been studied within the range 20–40°C in three media: (a) 0.04 M NaOH–glycine buffer (pH 9.1); (b) Aerosol OT (AOT) reversed micelles in octane; and (c) Triton X-100 micelles in octane supplemented with 10% hexanol. The enzyme inactivation was characterized quantitatively by first order rate constants, k _in(s^–1). In the case of G6PDH–NADP⁺complexes, the values of k _inwere independent of the initial concentrations of G6PDH, either in aqueous medium or AOT micelles. The values of k _infor the complex G6PDH–GP were inversely related to the initial concentration of the enzyme, in both aqueous and micellar media. When inactivation of both complexes were studied in AOT micelles, minimum values of k _incorresponded to the degree of hydration W ₀= 16.7; at W ₀> 16.7 and W ₀< 16.7, k _inincreased. Within the range 20–40°C, the values of k _inmeasured for both complexes in aqueous medium were significantly lower than those measured in AOT micelles. Temperature dependences of k _inwere characterized by inflections in Arrhenius plots, which corresponded, depending on the medium, to certain temperatures from 33.6°C to 40°C. In all media studied, NADP⁺complexes of the enzyme exhibited higher stability than their GP counterparts. The parameters of G6PDH and G6PDH–NADP⁺melting, measured by differential scanning microcalorimetry (maximum temperature and half-width of the transition, enthalpy of denaturation, and van't Hoff enthalpy), provided unequivocal evidence of the higher stability of the complex as compared to that of the enzyme. In addition, this approach demonstrated that G6PDH undergoes destabilization in AOT micelles.     

Genetic Selection for Heat Tolerance and Low Temperature Activity of the Entomopathogenic Nematode–bacterium Complex <Emphasis Type="Italic">Heterorhabditis Bacteriophora</Emphasis>–<Emphasis Type="Italic">Photorhabdus Luminescens</Emphasis>

The entomopathogenic nematode–bacterium complex Heterorhabditis bacteriophora–Photorhabdus luminescens is used in commercial biocontrol of insect pests. Tolerance and activity of the nematodes at extreme environmental conditions can limit the shelf life, quality and field performance of nematode-based products. To overcome these limitations, the potential for genetic improvement of the heat tolerance and the activity at low temperature was investigated. Heat tolerance and cold activity are quantitative traits, influenced by several genes and environmental factors. The breeding success for such traits depends on the genetic proportion on the phenotypic variability, the heritability, which was determined by recording the variability within and between homozygous inbred lines. The heritability for heat tolerance was 0.68 and for activity at low temperature 0.38. To increase heat tolerance, 4 selection steps were carried out, which increased the mean tolerated temperature from 38.5 to 39.2 °C. The mean temperature at which the dauer juveniles of H. bacteriophora were active, could be reduced from 7.3 to 6.1 °C during the first 5 selection steps. However, for unknown reasons, it increased during the following 5 steps to 7.1 °C. A screening among different P. luminescens isolates for growth at low temperature resulted in several cold-adapted strains from North America, which reached considerable cell density at 6 °C.     

Growth, survival, and starvation resistance of Colorado squawfish larvae

Synopsis Growth and survival of Colorado squawfish, Ptychocheilus lucius, larvae under fluctuating 18, 22, and 26° C (5° C diel fluctuations) and constant 18, 22, 26° C, and 30° C temperature conditions and ration size corresponding to 12.5, 28,64,142, 320 brine shrimp nauplii fish^–1 day^–1 determined from laboratory experiments. Growth was optimal at 31° C and high at temperatures of 26° C to 30° C, at the highest food abundance. Lowest growth was under lowest food rations and highest temperatures. Growth of Colorado squawfish larvae declined substantially at temperatures < 22° C. Neither growth nor survival was significantly different between fluctuating or constant regimes. Survival of Colorado squawfish larvae was highest (95%) at 26.2° C and 235 nauplii fish^–1 day^–1 and high at temperatures of 20 to 30° C with food abundance > 180 nauplii fish^–1 day^–1. Survival was lowest when food abundance was low and temperature was high. Highest mortality occurred more than 20 days after experiments began and mortalities occurred sooner in higher than lower temperatures. Colorado squawfish larvae denied food for 5, 10, or 15 d after first feeding could have begun (6 d), had survival greater than 87 % which was equivalent to continuously fed controls. Survival of fish denied food for 17.5 d after feeding could have begun declined from 84% before feeding to 57% after feeding. Point of no return was estimated between 17.5 and 20 d. Colorado squawfish have relatively high starvation resistance. Low, stable flows that simulate natural hydrographs may enhance growth, survival, and recruitment of early life stages of Colorado squawfish by increasing water temperature and food abundance in regulated rivers of the Colorado River basin.     

Temperature,light, and photoperiod responses of some Northeast American and West European endemic rhodophytes in relation to their geographic distribution

The relationship between distributional boundaries and temperature responses of some Northeast American and West European endemic and amphiatlantic rhodophytes was experimentally determined under varying regimes of temperature, light, and daylength. Potentially critical temperatures, derived from open ocean surface summer and winter isotherms, were inferred from distributional data for each of these algae. On the basis of the distributional data the algae fall within the limits of three phytogeographic groups: (1) the Northeast American tropical-to-temperate group; (2) the warm-temperate Mediterranean Atlantic group; and (3) the amphiatlantic tropical-to-warm temperate group. Experimental evidence suggests that the species belonging to the northeast American tropical-to-temperate group(Grinnellia americana, Lomentaria baileyana, andAgardhiella subulata) have their northern boundaries determined by a minimum summer temperature high enough for sufficient growth and/or reproduction. The possible restriction of 2 species (G. americana andL. baileyana) to the tropical margins may be caused by summer lethal temperatures (between 30 and 35 °C) or because the gradual disintegration of the upright thalli at high temperatures (>30 °C) promotes an ephemeral existence of these algae towards their southern boundaries. Each of the species have a rapid growth and reproductive potential between 15–30 °C with a broad optimum between 20–30 °C. The lower limit of survival of each species was at least 0 °C (tested in short days only). Growth and reproduction data imply that the restrictive distribution of these algae to the Americas may be due to the fact that for adequate growth and/or reproduction water temperatures must exceed 20 °C. At temperatures 15 °C reproduction and growth are limited, and the amphiatlantic distribution through Iceland would not be permitted. On the basis of experimental evidence, the species belonging to the warm-temperate Mediterranean Atlantic group(Halurus equisetifolius), Callophyllis laciniata, andHypoglossum woodwardii), have their northern boundaries determined by winter lethal temperatures. Growth ofH. equisetifolius proceeded from 10–25 °C, that ofC. laciniata andH. woodwardii from 5–25 °C, in each case with a narrow range for optimal growth at ca. 15 °C. Tetrasporelings ofH. woodwardii showed limited survival at 0 °C for up to 4 d. For all members of the group tetrasporangia occurred from 10–20 °C. The southern boundary ofH. equisetifolius andC. laciniata is a summer lethal temperature whereas that ofH. woodwardii possibly is a winter growth and reproduction limit. Since each member of this group has a rather narrow growth and survival potential at temperatures <5 °C and >20 °C, their occurrence in northeast America is unlikely. The (irregular) distribution ofSolieria tenera (amphiatlantic tropical-to-warm temperate) cannot be entirely explained by the experimental data (possibly as a result of taxonomic uncertainties).Paper presented at the Seaweed Biogeography Workshop of the International Working Group on Seaweed Biogeography, held from 3–7 April, 1984 at the Department of Marine Biology, University of Groningen (The Netherlands). Convenor: C. van den Hoek.     

Effects of temperature on the darkness survival of marine microplanktonic algae

Thirty-seven species of marine microplanktonic algae from 10 taxonomic classes were tested for their viability in axenic culture after prolonged exposure to darkness at 2°, 10°, and 20°C. The darkness test periods were prolonged in weekly installments up to a maximum of 1 year, and viability retention (survival) was judged from the capability for resuming growth after replacement in light. The 2°C-tests showed 32% of the species reaching the limits of survival with 5–6 months of darkness exposure, but another similar percentage continued to tolerate darkness for double this period. These darkness toleration limits were considerably shorter at 20°C for the strains known to be isolated from cold marine regions, whereas the warm-water strains showed the reverse temperature effect in surviving significantly longer at 10°–20°C than at 2°C. Irrespective of temperature or algal class, the bulk of the more resistant survivors was formed by the strains qualifying as benthic types, about 70% of which tolerated 11–12 months and the rest at least 5–6 months of darkness. A few randomly chosen benthic strains extended this toleration to 3 years of darkness. It was concluded that phytoplankters retain darkness-endurance capacity determined by their ecological origin and with no obvious taxonomic correspondence. The concept of ecological races, characterized by temperature control of darkness survival, is discussed.The termdarkness-survival is used throughout this report to denote the retention of cellular viability by an algawithout growth (i.e., without significant increase in cellular mass or numbers) during exposure to darkness. Implicit in this definition is the denial of any known possibility of growth, either autotrophic requiring light or heterotrophic requiring organic-carbon, since both these agents are effectively absent in the survival cases considered here.     

Growth kinetics of Thermus thermophilus

Summary The nonsporulating extreme thermophile Thermus thermophilus was grown in continuous culture at dilution rates up to 2.65 h^–1 at 75°C and pH 6.9 on complex medium. Concomitantly very low yield (Y=0.12 g cell dry weight g^–1 utilized organic carbon) and incomplete substrate utilization (always less than 45%) were found. In batch cultures T. thermophilus could be grown with _max =h^–1, in shake flasks only with _max =h^–1 with the same low yield and incomplete substrate utilization. Stable steady states at 84C and 45°C were realized at a dilution rate of 0.3 h^–1 whereas at 86°C and 40°C no growth could be detected. Artefacts arising from wall growth (in bioreactors) or improper materials must be ruled out. Inhibition of growth by organic substrates was demonstrated at low concentrations: a decrease in the yield obtained was found when more than 0.7 gl^–1 of meat extract were supplied in the medium. The maintenance requirement for oxygen is potentially very high and was determined to be 10 to 15 mmol g^–1 h^–1.     

Aspects of the thermal ecology of the rusty crayfish Orconectes rusticus (Girard)

Summary Orconectes rusticus currently is undergoing an explosive range expansion in the midwestern U.S.A., but information on the potentially important effects of water temperature on the species' biology is lacking. The thermal ecology of O. rusticus in southwestern Ohio, U.S.A., was examined by determining 1) the effects of four water temperatures (16, 20, 25, and 29°C) on survival and growth of juveniles, 2) the responses of juveniles and adults to a thermal gradient (7–27° C), and 3) the thermal tolerances (critical thermal maximum, CTMax, and critical thermal minimum, CTMin) of free-living, field-acclimatized juveniles and adults on a biweekly basis throughout the summer. Month-long growth experiments predicted maximum growth rates of juveniles at water temperatures between 26 and 28°C, but greatest survival between 20 and 22° C. Laboratory-acclimated (22° C) adults and field-acclimatized (2.5° C) juveniles both had an acute preferred temperature of 22° C. CTMaxs and CTMins of juveniles were 0.5–2.6° C higher than those of adults throughout the summer, suggesting that juveniles were exposed to water temperatures 1.5–6.8° C warmer than those of adults. Juvenile and adult O. rusticus prefer habitats where water temperatures favor maximum survival, but they usually are not found together in the same habitat; adults apparently displace the juveniles into warmer habitats. Warmer temperatures can decrease survival of juveniles but improve their growth rates, leading to enhanced fecundity and competitive ability. The past and future success of O. rusticus in expanding its range may depend, in part, on the species ability to adjust to new thermal environments occupied by other species of crayfish.     

Survival of adults and developmental stages ofSarcoptes scabiei var.canis when off the host

All life-stages ofSarcoptes scabiei var.canis survive in the hosts' environment for several days to several weeks depending on r.h. and temperature. Survival of larvae was comparable to males; survival of nymphs was comparable to females. Females and nymphs generally survived longer than larvae and males.Low temperature (10–15°) and high r.h. prolonged survival of all life stages. At 10–15°C, females and nymphs survived 1–3 weeks at 97% r.h., 1–2 weeks at 75% r.h. and 5–8 days at 45% r.h. At 20–25°C, survival was significantly reduced but all life-stages survived at least 2 days at 25% r.h. and 5–6 days at 75–100% r.h. Long survival off the host coupled with host-seeking behavior of these mites make it likely that environmental contamination is a source of scabies in domestic and wild mammals, and in humans.     

Adaptations to terrestrial overwintering of hatchling northern map turtles,<Emphasis Type="Italic"> Graptemys geographica</Emphasis>

We conducted a 3-year field and laboratory study of winter biology in hatchlings of the northern map turtle (Graptemys geographica). At our study area in northern Indiana, hatchlings routinely overwintered in their natal nests, emerging after the weather warmed in spring. Winter survival was excellent despite the fact that hatchlings were exposed frequently to subfreezing temperatures (to –5.4 °C). In the laboratory, cold-acclimated hatchlings exhibited low rates of evaporative water loss (mean=2.0 mg g^–1 day^–1), which would enable them to conserve body water during winter. Laboratory-reared hatchlings were intolerant of freezing at –2.5 °C for 24 h, conditions that are readily survived by freeze-tolerant species of turtles. Winter survival of hatchling G. geographica probably depended on their extensive capacity for supercooling (to –14.8 °C) and their well-developed resistance to inoculative freezing, which may occur when hatchlings contact ice and ice-nucleating agents present in nesting soil. Supercooled hatchlings survived a brief exposure to –8 °C. Others, held at –6 °C for 5 days, maintained ATP concentrations at control levels, although they did accumulate lactate and glucose, probably in response to tissue hypoxia. Therefore, anoxia tolerance, as evidenced by the viability of hatchlings exposed to N₂ gas for 8 days, may promote survival during exposure to subfreezing temperatures.Abbreviations EWL evaporative water loss - FP_eq equilibrium freezing point - INA ice-nucleating agents - T_c temperature of crystallizationCommunicated by L.C.-H. Wang     

Changes in gill morphology of Oreochromis mossambicus subjected to heat stress

Synopsis The cichlid fish, Oreochromis mossambicus, was acclimated to 25°C for a 14 day period and then subjected to elevated temperatures of 30, 35, 40 and 45° C. Gill epithelia was progressively damaged from 30–40° C; gills from fish tested at 45°C showed less damage than those tested at 40°C. This is presumably due to the shorter exposure (survival) time at 45°C. Shrinkage of the secondary lamellae and the collapse of pillar cells supports the hypothesis that hypoxia at elevated temperatures is partially a function of changes in gill morphology.     

Bionomics and population growth statistics of apterous virginoparae of woolly apple aphid, Eriosoma lanigerum, at constant temperatures

Development, survival, reproduction and population growth statistics of apterous virginoparae of woolly apple aphid, Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) at constant temperatures of 10, 13, 15, 20, 25, 30 and 32°C are reported. The developmental times of all life stages were inversely related to temperature ranging from 10 to 30°C. Span of total development (time from birth to adulthood) decreased from 57.8 days at 10°C to 11.7 days at 30°C and increased to 16.8 days at 32°C. A good linear model fit (R²>0.96) between developmental rate and temperature in the range 10–25°C was observed for all life stages. The lower developmental threshold was estimated at 5.8°C for instar I, 4.8°C for instar II, 4.9° for instar III and 4.4°C for instar IV. The lower temperature threshold for total development was estimated at 5.2°C. The upper developmental limit was found to be 32°C. Mean degree-day accumulations required for completion of instars I, II, III, IV and total development were: 125.6, 51.0, 47.7, 50.7 and 267.6, respectively. Fecundity, larviposition period and adult longevity were reduced with increasing temperature. Net reproductive rate was greatest at 15°C whereas intrinsic rate of increase peaked at 25°C. Optimal performance, as measured by fecundity, survival and intrinsic rate of increase, ocurred in the range 13–25°C.     

Hydrolysis of Heparin by the Immobilized Enzymatic Complex from Streptomyces kurssanovii

The possibility of obtaining low-molecular-weight heparins using a chitinolytic enzymatic complex immobilized on Silochrom has been demonstrated. The optimal conditions of this process (sodium acetate buffer, pH 7.0–7.5; temperature, 40–45°C; and duration of hydrolysis, 3 h) were determined. Depending on the ratio between heparin and the immobilized enzymatic complex, samples with molecular weights varying from 1.7 to 4.7 kDa, were obtained. These complexes inhibited factor Xa 2.0–3.7 times more effectively than the original heparin.