The combined relationship of temperature and molybdenum concentration to nitrogen fixation byAnabaena cylindrica

The joint effects of growth temperature, incubation temperature, and molybdenum concentration on the nitrogen fixation rate ofAnabaena cylindrica were determined using the acetylene-reduction technique. The nitrogen-fixation response to increased molybdenum concentration varied among three growth temperatures (15°, 23°, and 30° C). The pattern of rate change was similar within a growth temperature but increased overall in magnitude with the three incubation temperatures (also 15°, 23°, and 30° C). The maximum rate of nitrogen fixation occurred at 30°C regardless of previous growth temperature. The minimum molybdenum concentration necessary to yield substantial acetylene reduction varied with growth temperature: at 15°C, 15g 1^–1 was effective; at 23°C, less than 5g 1^–1 was effective; and at 30°C, 50g 1^–1 was effective. At all three growth temperatures, increases in molybdenum concentration above the minimum effective concentration produced increases in acetylene reduction. However, at higher molybdenum concentrations inhibition of nitrogen fixation occurred.     

Swimming Performances of Four California Stream Fishes: Temperature Effects

The critical swimming velocity (U_crit) of four California stream fishes, hardhead, Mylopharodon conocephalus, hitch, Lavinia exilicauda, Sacramento pikeminnow, Ptychocheilus grandis, and Sacramento sucker, Catostomus occidentalis was measured at 10, 15, and 20°C. Hardhead, Sacramento sucker, and Sacramento pikeminnow swimming performances tended to be lowest at 10°C, higher at 15°C, and then decreased or remained constant at 20°C. Hitch swimming performance was lower at 10°C than at 20°C. There were no significant differences among species at 10 or 15°C, although pikeminnow and hitch were ca. 20% slower than hardhead or sucker. At 20°C hardhead, Sacramento sucker, and Sacramento pikeminnow had remarkably similar U_crit but hitch were significantly (by 11%) faster. We recommend that water diversion approach velocities should not exceed 0.3ms^–1 for hitch (20–30cm total length) and 0.4ms^–1 for hardhead, Sacramento pikeminnow, and Sacramento sucker (20–30cm TL).     

A comparison of proline, thiol levels and GAPDH activity in cyanobacteria of different origins facing temperature-stress

Three cyanobacterial strains originating from different habitats were subjected to temperature shift exposures and monitored for levels of proline, thiol and activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Thermophile Mastigocladus laminosus (growth optimum, 40 °C), raised the proline level 4.2-fold at low temperature (20 °C), for the psychrophile Nostoc 593 (growth optimum, 20 °C), it was raised 8-fold at 40 °C while in the mesophile Nostoc muscorum (growth optimum, 30 °C), the imino acid level increased 2.3-fold during temperature shiftdown to 20 °C or 3.5-fold in sets facing shiftup (40 °C). Alterations in thiol levels in the above strains were in line with proline. It is suggested that such fluctuations reflect metabolic shifts as a response to stress. Interestingly, GAPDH activity was maximum at the respective growth temperature optimum of M. laminosus (122 nmol NADPH oxidized min ^–1 mg ^–1 protein) and Nostoc 593 (141 nmol NADPH oxidized min ^–1 mg ^–1 protein) while in N. muscorum, it increased at 40 °C (101 nmol NADPH oxidized min ^–1 mg ^–1 protein) and to 93.3 nmol NADPH oxidized min ^–1 mg ^–1 protein (20 °C) relative to 86 nmol NADPH oxidized min ^–1 mg ^–1 protein at 30 °C. It seems that extremophiles maintain the GAPDH activity/level during growth at their respective temperatures optimal while the mesophile increases it in order to cope up with temperature-stress.     

Growth of the Annual Fish, Cynolebias Viarius (Cyprinodontiformes), in the Natural Habitat Compared to Laboratory Conditions

For the first time, growth throughout the life cycle of an annual fish, Cynolebias viarius, was assessed in the wild, within a temporary pool located in eastern Uruguay. Before pools dry out at the beginning of the warm season, C. viarius deposit eggs in the sediment. Embryos hatch when precipitation fills the pools again in March–April. During 1996, at biweekly or monthly intervals, environmental conditions were monitored and the length of 20 to 55 C. viarius measured. Pool size varied between 109 and 475m², respectively. Water depth at its center reached between 10 (June) and 35cm (September). Water temperatures ranged from 6°C in June to 28.8°C in November. The water was slightly acidic (pH = 6.3 ± 0.2) and subsaturated with O₂ (48–88%); conductivity averaged 258 ± 39Scm^–1. On the first field trip after inundation (May 2), mean length of C. viarius was 9.9 ± 1.0mm. Maximum growth rate (0.66mm per day) was determined during the following two-week-interval and was associated with relatively high water temperatures (20–22°C). While fish length remained virtually unchanged during the colder winter months, C. viarius manifested growth, specially in weight, during the last third of the life cycle. Fish were sexually mature at 8 (67%) to 18 (100%) weeks of age. In the laboratory, specimens held at 25°C grew faster and reached sexual maturity at an earlier age (11 weeks) than at 15°C (10–16 weeks). Over the 5-months study period, mortality reached 37.5% at 15°C and 100% at 25°C. Results are compared to information available from other annual fishes.     

The effects of temperature on feeding in zooplanktivorous walleye,Stizostedion vitreum,larvae

Synopsis We examined the prey capture process in walleye larvae (9.8–18.0 mm mean length) feeding on zooplankton (density 1501^–1) in laboratory aquaria at 15,18.5 and 22°C. Larvae were starved for 8 h prior to the experiment and only allowed to feed for 10 min during the experiment in order to minimize the influence of gut processing or satiation on feeding behaviour. Prey consumption (g min^–1) increased exponentially and prey capture success (%) increased logarithmically with mean walleye length. Prey consumption and attack rate (strikes min^–1) increased significantly with increasing temperature. The effect of temperature on capture success was slight (2% increase from 15 to 22°C) and not significant. Walleye showed positive electivity for medium-sized prey (0.3–0.6 mm body width, mostlyCeriodaphnia quadrangula), negative electivity for small prey (0.3 mm, mostly cyclopoid copepods) and neutral electivity for large prey (0.6 mm, mostlyDaphnia sp.). Neither prey species electivity nor prey size electivity were significantly affected by temperature. However, prey size electivity did show a fairly large effect size with respect to temperature and we suggest that this relationship should be examined further. These results indicate that temperature affects prey capture in walleye larvae primarily by influencing attack rate.     

Abscisic acid and mefluidide in the regulation of cold hardiness development in Solanum tuberosum L. potato

Plants of Solanum tuberosum L. potato do not cold acclimate when exposed to low temperature such as 5°C, day/night. When ABA (45 M) was added to the culture medium, stem-cultured plantlets of S. tuberosum, cv. Red Pontiac, either grown at 20°C/15°C, day/night, or at 5°C, increased in cold hardiness from –2°C (killing temperature) to –4.5°C. The increase in cold hardiness could be inhibited in both temperature regimes if cycloheximide (70 M) was added to the culture medium at the inception of ABA treatment. Cycloheximide did not inhibit cold hardiness development, however, when it was added to the culture medium 3 days after ABA treatment.When pot-grown plants were foliar sprayed with mefluidide (50 M), ABA content increased from 10 nmol to 30 nmol g^–1 dry weight and plants increased in cold hardiness from –2°C to about –3.5°C. The increases in free ABA and cold hardiness occurred only in plants grown at 20°C/15°C; neither ABA nor cold hardiness increased in plants grown at 5°C.The results suggest that an increase in ABA and a subsequent de novo synthesis of proteins are required for the development of cold hardiness in S. tuberosum regardless of temperature regime, and that the inability to synthesize ABA at low temperature, rather than protein synthesis, appears to be the reason why S. tuberosum does not cold acclimate.     

Influence of environmental factors on the growth in culture of a New Zealand strain of the fast-spreading algaHydrodictyon reticulatum (water-net)

Hydrodictyon reticulatum (L.) Lagerh. is a recent addition to the New Zealand flora and is expanding its distribution rapidly. Proliferations of the alga now constitute an economic nuisance in waters which have not previously suffered filamentous algal blooms. To better understand the current and likely future spread of the alga and to identify possible management options the alga's growth requirements have been investigated. A strain isolated from New Zealand tolerated temperatures between 5 and 40 °C and salinities from 0 to 5. Optimal growth was at 25 °C, 150 mol photon m^–2s^–1 and in freshwater. Nett photosynthesis was saturated at photon flux densities of 100 and 160 mol m^–2s^–1 at 12 and 20 °C, respectively. Growth rate was linearly related to internal N concentration and hyperbolically to internal P concentration. Minimum cellular nutrient contents, by weight, were 1% N and 0.2% P. Growth was saturated at contents of 5% N and 0.5% P under the conditions of culture (20 °C, 150 mol photon m^–2s^–1). The alga maintained optimal cellular N content at low ambient nitrate concentrations (100 mg m^–3) half optimum content at 18 mg m^–3. Affinity for filtrable reactive phosphorus was not unusually high compared to other filamentous algae. We suggest that this alga is occupying a niche in New Zealand which has been precluded from other filamentous nuisance algae by low N concentration and N:P ratio. The significance of these findings in setting environmental targets for management of this nuisance alga is discussed.Author for correspondence     

Diversity and cold-active hydrolytic enzymes of culturable bacteria associated with Arctic sea ice,Spitzbergen

The diversity of culturable bacteria associated with sea ice from four permanently cold fjords of Spitzbergen, Arctic Ocean, was investigated. A total of 116 psychrophilic and psychrotolerant strains were isolated under aerobic conditions at 4°C. The isolates were grouped using amplified rDNA restriction analysis fingerprinting and identified by partial sequencing of 16S rRNA gene. The bacterial isolates fell in five phylogenetic groups: subclasses and of Proteobacteria, the Bacillus–Clostridium group, the order Actinomycetales, and the Cytophaga–Flexibacter–Bacteroides (CFB) phylum. Over 70% of the isolates were affiliated with the Proteobacteria subclass. Based on phylogenetic analysis (<98% sequence similarity), over 40% of Arctic isolates represent potentially novel species or genera. Most of the isolates were psychrotolerant and grew optimally between 20 and 25°C. Only a few strains were psychrophilic, with an optimal growth at 10–15°C. The majority of the bacterial strains were able to secrete a broad range of cold-active hydrolytic enzymes into the medium at a cultivation temperature of 4°C. The isolates that are able to degrade proteins (skim milk, casein), lipids (olive oil), and polysaccharides (starch, pectin) account for, respectively, 56, 31, and 21% of sea-ice and seawater strains. The temperature dependences for enzyme production during growth and enzymatic activity were determined for two selected enzymes, -amylase and -galactosidase. Interestingly, high levels of enzyme productions were measured at growth temperatures between 4 and 10°C, and almost no production was detected at higher temperatures (20–30°C). Catalytic activity was detected even below the freezing point of water (at –5°C), demonstrating the unique properties of these enzymes.     

Growth characteristics of an obligately psychrophilic Vibrio sp.

The growth characteristics of an obligately psychrophilic Vibrio sp. have been studied in a chemostat with glucose or lactose as the limiting substrate over a temperature range 0–23°C. Vibrio AF-1 has an optimum growth temperature of 15°C and maximum growth temperature which is dependent upon the carbon source. On glucose growth ceases at 20°C whereas on lactose growth continues to 23°C. Growth rate is also a function of the carbon source provided. When grown on glucose, fructose, sucrose, maltose and galactose _max values of 0.046 h^-1 at 15°C were recorded whereas on lactose, mannose, ribose and xylose _max values of 0.020 h^-1 were obtained. Substrate affinities (K _s ) for the 9 sugars also fall into 2 divisions as for _max and are temperature dependent. Those sugars which support a high growth rate have highest K _s values at 0°C whereas these which give a low growth rate show maximum affinities at 15°C. Vibrio AF-1 produces the maximum cell yield (0.6 g/g sugar consumed) at temperature <8°C irrespective of the carbon source utilised and correlated with maximum rates of sugar uptake and minimum O₂ consumption. Maintenance energy determination on glucose grown cells show that at 2° C 2% of the carbon input is used for maintenance whereas at 20°C the requirement increases to 10% of the carbon input.     

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.     

Comparative population growth and life table demography of the rotifer Asplanchna girodi at different prey (Brachionus calyciflorus and Brachionus havanaensis) (Rotifera) densities

Population growth and life table demography of the predatory rotifer A. girodi using spineless Brachionus calyciflorus and spined Brachionus havanaensis as prey at densities of 1, 2, 4 and 8 ind. ml^–1 at 25°C were studied. Regardless of the prey species, the population of A. girodi increased with increasing availability of Brachionus in the medium. At any given prey density, A. girodi fed B. calyciflorus showed consistently better growth than when fed B. havanaensis. The maximum population densities of A. girodi varied from 0.28 to 1.8 ind. ml^–1 depending on the prey species and the density. The rate of population increase observed in population growth studies varied from 0.17 to 0.43 day^–1 when fed B. calyciflorus and 0.09 to 0.27 day^–1 when fed B. havanaensis. Male population of A. girodi was closely related to female density. The lowest average lifespan was observed for A. girodi when fed B. havanaensis at 1 ind. ml^–1, while the converse was the case when fed B. calyciflorus at comparable prey concentration. Net reproductive rates varied from 16 to 26 offspring female^–1 lifespan^–1 depending on the prey species and concentration. Generation time of A. girodi decreased with increasing food concentrations for both the prey species. The rates of population increase obtained from life table demography were lower for A. girodi when fed B. havanaensis than when fed B. calyciflorus.     

Growth and lactic acid production ofPediococcus pentosaceus at different gas environments,temperatures, pH values and nitrite concentrations

Summary In order to obtain a better understanding of the behaviour ofPediococcus pentosaceus in food products as well to facilitate the designing of industrial production processes for the organism, the growth and lactic acid production ofPediococcus pentosaceus in a complex glucose medium was followed in batch cultures at different gas environments (CO₂, air, N₂ and static cultures without gasflow), temperatures (10–50°C), pH (4.3–7.3) and nitrite concentrations (0–700 ppm). Optimal growth was obtained in CO₂ at 40°C and pH 6.3 and resulted in a maximum specific growth rate ( _max) of 1.27 h^–1. In static culture at 40°C and pH 6.3 the _max was 1.21 h^–1. The _max was, compared with static culture, reduced in air (12%) and nitrogen (26%). At 10°C the _max was reduced by 99% and at 50°C by 88%. The reduction at pH 4.3 and 7.3 was 65% and 57%, respectively. Nitrite did not affect the _max at any pH but increased the lag phase at pH 4.3 by a factor of 12. The lactic acid production was linked to the growth. The total amount of lactic acid produced was the same in all the tested gases and nitrite concentrations and also within the wide temperature range (15–45°C) and pH range (5.3–7.3). Mainly L(+)-lactic acid was produced during the exponential growth phase, but after this growth declined about 30% of the L(+)-lactic acid was converted to D(–)-lactic acid. The lactic acid product yield and the cellmass yied were both affected by the temperature but not by the pH.     

Growth of two Pisidium (Bivalvia,Sphaeriidae) species in the laboratory

Summary Growth of Pisidium casertanum and P. subtruncatum from the profundal of the eutrophic Lake Esrom was followed at four temperatures in the laboratory. The growth rate of both species increased with increasing temperature, but the maximum in P. casertanum was attained at 12° C, instead of at 20° C as in P. subtruncatum. The variation of Q₁₀ of growth in relation to animal weight was of similar form in both species at higher temperatures (6–12°C) but opposite at low temperatures (2–6°C). In the latter case Q₁₀ of P. casertanum had a peak and that of P. subtruncatum a low value at a corresponding size preceding maturity. At constant temperatures growth curves of the form y=a+bx+cx² were obtained, where y is weight in g and x is time in days. The growth of both species under natural conditions was simulated by use of the experimental growth rate equation and natural birth periods, sizes at birth, and temperature cycles. These simulations gave a maximum life span of 2.5–3 years for P. casertanum and 3.5–4.5 years for P. subtruncatum. The latter species showed slower growth rates at the low or medium temperatures prevailing in the profundal of this lake. A comparison with growth in nature reveals that the simulation overestimated growth in case of P. casertanum.     

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.     

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.     

Light-temperature interactions on the growth of Antarctic diatoms

Summary The combined effect of various temperatures and light intensities on the growth of seven species of antarctic diatoms in culture has been studied. With the exception of Chaetoceros deflandrei whose thermal tolerance is fairly good, these obligatory psychrophils cannot survive in temperatures above 6° to 9° C. Their mean growth rate is relatively low, between 0.24 div d^–1 for Corethron criophilum and 0.63 div d^–1 for C. deflandrei. Regardless of light intensity, growth rate increased with the temperature to reach a maximum between 3° and 5° C. The highest rates were obtained between 115 and 220 mol m^–2 s^–1 with 0.38 div d^–1 for C. criophilum, 0.56 div d^–1 for Synedra sp. and between 0.71 and 0.88 div d^–1 for the other 5 species. A reduction in light intensity from 220 to 46 mol m^–2 s^–1 slowed growth by nearly 50%. These results suggest that the combined effect of temperature and light is one of the factors involved in the limitation of antarctic phytoplankton growth. The low temperatures of the environment do not permit rapid growth, which, even under optimal light conditions remains low. In addition, in the euphotic layer, the overall light energy available for algae is considerably reduced due to turbulence, a factor which exacerbates the reduced growth rate.     

Root-zone temperature and salinity: Interacting effects on tillering,growth and element concentration in barley

The effects of root-zone salinity (0, 30, and 60 mmol L^–1 of NaCl) and root-zone temperature (10, 15, 20, and 25°C) and their interactions on the number of tillers, total dry matter production, and the concentration of nutrients in the roots and tops of barley (Hordeum vulgare L.) were studied. Experiments were conducted in growth chambers (day/night photoperiod of 16/8 h and constant air temperature of 20°C) and under water-culture conditions. Salinity and root temperature affected all the parameters tested. Interactions between salinity and temperature were significant (p<0.05) for the number of tillers, growth of tops and roots, and the concentration of Na, K, P in the tops and the concentration of P in the roots. Maximum number of tillers and the highest dry matter were produced when the root temperature was at the intermediate levels of 15 to 20°C. Effect of salinity on most parameters tested strongly depended on the prevailing root temperature. For example, at root temperature of 10°C addition of 30 mmol L^–1 NaCl to the nutrient solution stimulated the growth of barley roots; at root temperature of 25°C, however, the same NaCl concentration inhibited the root growth. At 60 mmol L^–1, root and shoot growth were maximum when root temperature was kept at the intermediate level of 15°C; most inhibition of salinity occurred at both low (10°C) and high (25°C) root temperatures. As the root temperature was raised from 10 to 25°C, the concentration of Na generally decreased in the tops and increased in the roots. At a given Na concentration in the tops or in the roots, respective growth of tops or roots was much less inhibited if the roots were grown at 15–20°C. It is concluded that the tolerance of barley plant to NaCl salinity of the rooting media appears to be altered by the root temperature and is highest if the root temperature is kept at 15 to 20°C.     

Factors affecting oviposition and fecundity in the grain miteAcarus siro L. (Acarina:Acaridae), especially temperature and relative humidity

Oviposition and fecundity in the grain miteAcarus siro were studied at 5–30°C and 62.5–90% RH. At and above 20°C, 80% RH, mating and oviposition occurred soon after emergence, but at lower temperatures and humidities egg laying was progressively delayed from one to several days. Females needed to mate repeatedly in order to achieve maximum egg production, optimum conditions for which were 15°C, 90% RH, where total output per female averaged 435 with a maximum of 858. Oviposition rates were highest at higher temperatures, the mean daily rate at 20 and 25°C, 90% RH, rising to maximum levels of 28/29 eggs per female per day on day six.Oviposition followed clearly defined patterns, favourable conditions producing rapid increases in the mean daily oviposition rate to high peak levels reached at an early stage in the oviposition period. Less favourable conditions resulted in reduced outputs and lower, more uniform rates of egg laying. The mean oviposition period, varying with humidity, fell from 72–122 days at 5°C to 9–13 days at 30°C and the mean incubation period from 42–70 days at 5°C to 3–4 days at 30°C. Egg viability increased with increasing humidity but was little affected by temperature and unaffected by age of the female at time of oviposition.Males tended to live longer than females at most conditions; longevity—depending on humidity—averaging 13–15 days at 30°C and 129–175 days at 5°C. Adult life for females averaged 12–19 days at 30°C and 88–169 days at 5°C. An index of suitability, calculated from egg number, viability and duration of the egg stage and oviposition period, indicated that the most favourable conditions for oviposition and hatching were 20–25°C and 80–90% RH.     

Production of extracellular lactase fromFusarium moniliforme

Summary A strain ofFusarium moniliforme, previously used for microbial protein production, excreted lactase (-D-galactosidase, EC.3.2.1 23) when cultivated either in a whey liquid medium or on a wheat bran solid medium. The enzyme produced in both media had pH and temperature optima of 4–5 and 50–60°C respectively and was particularly suitable for processing acid whey.In the whey culture, maximum lactase yield was observed after 95 h of growth at 30°C and whey lactose concentration of 9%. The addition of ammonium, potassium and sodium ions to the growth medium considerably enhanced lactase production. A maximum enzyme yield corresponding to hydrolysis of 3 nmoles o-nitrophenyl--D-galactopyranoside sec^–1 ml^–1 of growth medium, at pH 5 and 60°C, was obtained.In the wheat bran culture, the maximum enzyme yield was obtained after 140 h of growth at 28–30°C. A marked increase in the enzyme production was observed when nitrate or phosphate was added to the growth medium. Also, the addition of certain agricultural by-products (molasses, whey) enhanced lactase production. The observed maximum yield corresponding to the hydrolysis of 182 nmoles of ONPG sec^–1 g^–1 of wheat bran, at pH 5 and 60°C, is comparable to that reported for certain microorganisms used commercially for lactase production.     

Photosynthesis and growth rates of Laurencia brongniartii J. Agardh (Rhodophyta, Ceramiales) in preparation for cultivation

Laurencia brongniartii is usually found at depths below 4 m, but can be found in shallow subtidal areas in crevices and on the walls of a coral reef in Amami Oshima Island, Kagoshima Prefecture, Japan, where irradiances were significantly lower than those at similar depths in open water. In preparation for the possible cultivation of this species for its antibiotic compounds, the effects of temperature and irradiance on photosynthesis and growth were measured. Photosynthesis and growth rates of L. brongniartii explants were highest at 26 and 28 °C, which closely corresponded to temperatures found during August to late December when it was most abundant. The estimated maximum photosynthesis rate (P _max) was 4.41 mol photon m^–2 s^–1 at 26 °C and 4.07 mol photon m^–2 s^–1 at 28 °C. Saturating irradiance occurred at 95 mol photon m^–2 s^–1 at 26 °C and 65 mol photon m^–2 s^–1 at 28 °C. In contrast, growth experiments at 41.7 mol photon m^–2 s^–1 caused bleaching of explants and the maximum growth rate observed during the study was 3.02 ± 0.75% day^–1 at 28 °C and 25 mol photon m^–2 s^–1. The difference in the saturating irradiance for photosynthesis and the irradiance that caused bleaching in growth experiments suggests that long-term exposure to high irradiance was detrimental and should be addressed before the initiation of large scale cultivation.