Effect of desiccation level and storage temperature on green spore viability of Osmunda japonica

In order to effectively preserve green spores, which have relatively higher water content and lose viability more quickly than non-green spores, we studied the effect of desiccation level and storage temperature on Osmunda japonica spores. The water content of fresh spores was 11.20%. After 12 h desiccation by silica gel, the water content decreased to 6% but spore viability did not change significantly. As the desiccation continued, the decrease in water content slowed, but spore viability dropped. For almost all storage periods, the effects of storage temperature, desiccation level, and temperature × desiccation level were significantly different. After seven days of storage, spores at any desiccation level stored at 4 °C obtained high germination rates. After more than seven days storage, liquid nitrogen (LN) storage obtained the best results. Storage at −18 °C led to the lowest germination rates. Spores stored at room temperature and −18 °C all died within three months. For storage at 4 °C and in LN, spores desiccated 12 and 36 h obtained better results. Spores without desiccation had the highest germination rates after being stored at room temperature, but suffered the greatest loss after storage at −18 °C. These results suggest that LN storage is the best method of long-term storage of O. japonica spores. The critical water content of O. japonica spores is about 6% and reduction of the water content to this level improves outcome after LN storage greatly. The reason for various responses of O. japonica spores to desiccation and storage temperatures are discussed.     

Influence of Temperature and Relative Humidity on Germinability of Mucor piriformis Spores

Studies were conducted to determine the influence of temperature and relative humidity (RH) on germinability and viability of Mucor piriformis spores. Spores did not survive when stored at 35 °C and their survival rate decreased rapidly at 30 °C; however, spores remained viable for more than 1 year at 0 °C. RH also significantly affected spore viability. Spores held at 26 °C and 100% RH no longer germinated after 35 days, while those held at 75 or 90% RH germinated for 65 days. At 20 °C, RH had little effect on spore germinability. The effect of temperature and RH on percentage spore germination also varied. At all temperatures studied, spore viability decreased more rapidly with time at 100% RH than at 75 or 90% RH. The least favorable, temperature-humidity combination, 30 °C and 100% RH, decreased spore germination from 100% to less than 1% in 14 days.     

The response of bacterial spores to vacuum treatments. II. Germination and viability studies.

The viability of Bacillus megaterium spores has been determined after exposure to vacuum dehydration at temperatures between 0 and 65 °C, for periods up to 24 hr. A curvilinear relationship has been demonstrated between viability and drying temperature, with minimum viability occuring around 15 °C and increases in viability being shown above 35 °C. In contrast to vegetative bacteria, reequilibration of the dried spores to 2 × 10^?3 or 10 Torr aqueous vapor pressure, and/or subsequent exposure to oxygen had no effect on viability. Dehydration, rehydration and oxygen treatments had no effect on the time for outgrowth of the spores or on the growth rate of the resultant vegetative cells. Physical loss of spores from samples was not demonstrated during any of these treatments. Evidence has been presented for a novel type of spore activation, which occurs during vacuum dehydration at high temperatures, to an extent that is dependent upon drying time. The mechanism of this activation is unlike that of conventional heat or chemical activation but is oxygen independent and unaffected by reequilibration to 2 × 10^?3 or 10 Torr.     

The effect of high temperatures on spore germination of Ascosphaera aggregata

Vials containing spores of Ascosphaera aggregara were subjected to temperatures of 65°, 75°, 85°, and 95°C for 8-, 16-, and 24-hr periods at each temperature level in order to simulate disinfection heat treatments and determine the effect of temperature on spore viability. Significant (P > 0.0001) differences were noted for spore germination after heat treatment relative to the origin of the spores, the temperatures to which they were exposed, and for the duration of the heat treatment. An analysis of test responses of all isolates demonstrated significant overall differences in germination by geographic location of origin and temperature relative to duration of the treatment, by location and treatment duration relative to temperature, and temperature and duration of treatment relative to the geographic location of origin.     

The influence of storage temperature on spore viability of Mattesia trogodermae (Protozoa: Neogregarinida)

The viability of Mattesia trogodermae spores stored at different temperatures was assessed by the percentage infection induced in 30-day-old Trogoderma glabrum larvae. Exposure to 73°C and higher temperatures for 30 min was lethal to the spores. Spores stored at ?19°C survived better than those stored at 26.7°, 3.5°, or ?30°C.     

Cellular damage during drying and storage of Trichoderma harzianum spores

Factors that cause cellular damage during the drying and storage of Trichoderma harzianum conidia were independently studied to determine their effects on spore viability. Specifically, thermal stress and dehydration levels (water activity, a_w = 0.1–0.7) were assessed for their effect on spore survival. In addition, environmental conditions, such as water activity and temperature, were evaluated during storage of the spores. T. harzianum spores produced in liquid culture are highly sensitive to thermal stress, but dehydration does not seem to be a factor that influences spore death during desiccation. An inverse correlation between spore survival and the specific concentration of malondialdehyde (MDA) was observed during storage, especially when the conidia moisture levels were lower than the monolayer moisture levels. We prepared spore suspensions without additives and spray-dried the samples. Our data showed that reduced sample viability was mainly caused by the temperature of the drying process, an effect that appears to be independent of water activity.     

Patterns of primary spore discharge of Entomophthora spp from the blue green aphid,Acyrthosiphon kondoi

Experiments were conducted to study the effects of time, temperature, and light regime on primary spore formation at 100% RH for the three major pathogens of Acyrothosiphon kondoi. Only small differences were detected between the continuous light and continuous dark regimes. Entomophthora obscura produced between 6 and 10 × 10³ primary spores mostly during the first 48 hr. Total primary spore production was similar at the five temperatures tested from 5° to 25°C. Entomophthora planchoniana produced large numbers of primary spores (about 5 × 10⁴ per aphid) only at temperatures between 10° and 20°C. The majority of primary spores were formed during the first 24 hr. Primary spore production with Entomophthora nr. exitialis ranged from about 10⁵ per aphid at 5° and 10°C to 3 or 4 × 10⁵ at 15° to 25°C, with most spores being formed during the first 48 hr. It is suggested that rainfall is more likely to be important for transmission of E. obscura and E. nr. exitialis than for transmission of E. planchoniana, and that E. obscura is likely to be the most important pathogen during cool or cold weather.     

Divergence of water balance mechanisms in two sibling species (Drosophila simulans and D. melanogaster): effects of growth temperatures

Drosophila simulans is more abundant under colder and drier montane habitats in the western Himalayas as compared to its sibling D. melanogaster but the mechanistic bases of such climatic adaptations are largely unknown. Previous studies have described D. simulans as a desiccation sensitive species which is inconsistent with its occurrence in temperate regions. We tested the hypothesis whether developmental plasticity of cuticular traits confers adaptive changes in water balance-related traits in the sibling species D. simulans and D. melanogaster. Our results are interesting in several respects. First, D. simulans grown at 15 °C possesses a high level of desiccation resistance in larvae (~39 h) and in adults (~86 h) whereas the corresponding values are quite low at 25 °C (larvae ~7 h; adults ~13 h). Interestingly, cuticular lipid mass was threefold higher in D. simulans grown at 15 °C as compared with 25 °C while there was no change in cuticular lipid mass in D. melanogaster. Second, developmental plasticity of body melanisation was evident in both species. Drosophila simulans showed higher melanisation at 15 °C as compared with D. melanogaster while the reverse trend was observed at 25 °C. Third, changes in water balance-related traits (bulk water, hemolymph and dehydration tolerance) showed superiority of D. simulans at 15 °C but of D. melanogaster at 25 °C growth temperature. Rate of carbohydrate utilization under desiccation stress did not differ at 15 °C in both the species. Fourth, effects of developmental plasticity on cuticular traits correspond with changes in the cuticular water loss i.e. water loss rates were higher at 25 °C as compared with 15 °C. Thus, D. simulans grown under cooler temperature was more desiccation tolerant than D. melanogaster. Finally, desiccation acclimation capacity of larvae and adults is higher for D. simulans reared at 15 °C but quite low at 25 °C. Thus, D. simulans and D. melanogaster have evolved different strategies of water conservation consistent with their adaptations to dry and wet habitats in the western Himalayas. Our results suggest that D. simulans from lowland localities seems vulnerable due to limited acclimation potential in the context of global climatic change in the western Himalayas. Finally, this is the first report on higher desiccation resistance of D. simulans due to developmental plasticity of both the cuticular traits (body melanisation and epicuticular lipid mass) when grown at 15 °C, which is consistent with its abundance in temperate regions.     

The significance of temperature during sporulation on the biology of pycnidiospores of Mycosphaerella ligiilicola

The germination, infectivity and survival of pycnidiospores obtained from cultures of Mycosphaerella ligulicola grown at 15 and 26 °C were compared. Spores formed at 26° (‘26° spores’) were less able to germinate at low relative humidities and showed a narrower temperature range for maximum germination after 6 h. At high spore densities 26° spores showed self-inhibition of germination and, over a range of lower densities, growth of their germ tubes was checked, which resulted in lower infection of leaf discs compared with 15° spores in which this phenomenon did not occur. The fungus could be recovered from un-sterile compost over a longer period after inoculation with 15° spores. Only after storage at a temperature well below zero was there a difference in viability between 15° and 26° spores. It is thought that the potential advantage of producing larger numbers of spores at 26° would be realized only under optimum conditions for dispersal and infection. The smaller number of spores produced at 15° are likely to be successful under natural conditions.     

Desiccation of the resurrection plant <Emphasis Type="Italic">Haberlea rhodopensis</Emphasis> at high temperature

Haberlea rhodopensis plants, growing under low irradiance in their natural habitat, were desiccated to air-dry state at a similar light intensity (about 30 μmol m⁻² s⁻¹) under optimal (23/20°C, day/night) or high (38/30°C) temperature. Dehydration of plants at high temperature increased the rate of water loss threefold and had a more detrimental effect than either drought or high temperature alone. Water deficit decreased the photochemical activity of PSII and PSI and the rate of photosynthetic oxygen evolution, and these effects were stronger when desiccation was carried out at 38°C. Some reduction in the amount of the main PSI and PSII proteins was observed especially in severely desiccated Haberlea leaves. The results clearly showed that desiccation of the homoiochlorophyllous poikilohydric plant Haberlea rhodopensis at high temperature had more damaging effects than desiccation at optimal temperature and in addition recovery was slower. Increased thermal energy dissipation together with higher proline and carotenoid content in the course of desiccation at 38°C compared to desiccation at 23°C probably helped in overcoming the stress.     

Heat resistance of Clostridium sordellii spores

The thermal destruction kinetics of Clostridium sordellii spores was studied in this research. Decimal reduction times (D values) for C. sordellii ATCC 9714 spores ranged between 175.60 min for D₈₀ (the D value for spore suspensions treated at 80 °C) and 11.22 min for D₉₅. The thermal resistance (Z) and temperature coefficient (Q₁₀) values of spores were calculated to be as high as 12.59 °C and 6.23, respectively. At 95 °C, the relative thermal death rate and relative thermal death time of C. sordellii ATCC 9714 spores were found to be 0.0085/min and 118 min, respectively, indicating that the death rate of spores was 118 times lower at 95 °C than at 121.1 °C. Heat treatments at up to 85 °C for 120 min failed to cause a 100-fold destruction in spore populations of C. sordellii ATCC 9714. By contrast, spore counts were reduced by 2log₁₀ cycles within 73 min and 23 min at 90 °C and 95 °C, respectively. This is the first published report of thermal inactivation of C. sordellii spores; however, further studies are needed to confirm these results in real food samples.     

Pleistophora oncoperae sp.n. (Protozoa: Microsporida) from Oncopera alboguttata (Lepidoptera: Hepialidae) in Australia

Pleistophora oncoperae sp.n. is described from adults and larvae of Oncopera alboguttata and O. rufobrunnea. The main site of infection was muscle, though fat body and connective tissue were also infected. Fresh pansporoblasts measured about 25 μm in diameter and contained 16 to 32 or more spores with a mean size of 5.9 × 3.1 μm. Macrospores measuring 7.7 × 4.4 μm were also seen. The mean polar filament length was 158 μm; ultrastructural studies showed that the filament is normally arranged in 14 coils (range, 13 to 20) at an angle of 53.5° to the axis of the spore. The species was found to be distinct from all previously described Pleistophora reported from Lepidoptera.     

First results from conservation studies of chlorophyllous spores of the Royal fern (Osmunda regalis, Osmundaceae)

Pteridophytes spore banks are a promising ex situ conservation tool used to increase the chances of survival of ferns, in fact that large quantities of germplasm with high genetic variation can be conserved in a small space with low economic and technical costs. However, methods to maintain the viability of chlorophyllous spores during storage are less understood.The aim of this study was to investigate the influence of long term storage on the viability of Royal Fern spores, which were stored under different conditions derived from various combinations of temperature and degrees of hydration. Survival and germination tests were performed after 1 and 28 months of storage. Our results showed the highest survival percentages for spores stored under Normal humidity at subzero temperatures (T = ? ?20 °C). These spores received no pre-treatment, dehydration, or cryoprotectants, which resulted in fast germination and gametophyte development which seemed to be stimulated by low temperatures.     

Fine structure of the microsporidan Abelspora portucalensis gen.n., sp.n. (Microsporida) parasite of the hepatopancreas of Carcinus maenas (Crustacea,Decapoda)

A new species of a microsporidan, Abelspora portucalensis, was found in the hepatopancreas of Carcinus maenas, forming white xenomas. Each xenoma seems to consist of an aggregate of hypertrophic host cells in which the parasite develops and proliferates. This cytozoic microsporidan being characterized by one uninucleate schizont giving rise to two sporonts, each originating two sporoblasts, resulting in two spores within a persistent sporophorous vacuole (pansporoblast) should be included in a new family Abelsporidae. In fresh smears most spores were 3.1–3.2 μm long and 1.2–1.4 μm wide. Fixed, stained, and observed in SUS mature spores measured 3.1 ± 0.08 × 1.3 ± 0.06 μm (n = 25 measurements). Spore cytoplasm was dense and granular, polyribosomes were arranged in helicoidal tape form. The polar filament was anisofilar and consisted of a single coil with 5–6 turns. The anchoring disc and and the anterior zone of the filament are surrounded by the polaroplast composed of two usual zones. In the anterior zone, the membrane of the polar filament is in continuity with the membranes of the polaroplast. The appearance of a microsporidan with described nuclear divisions in life cycle, spores shape and size, polaroplast and polar filament morphology and identity of the host suggests that we may erect a new genus Abelspora and a new species A. portucalensis (Portugal = Portucalem).     

Effect of high temperature on dehydration-induced alterations in photosynthetic characteristics of the resurrection plant Haberlea rhodopensis

The effect of high temperature (HT) and dehydration on the activity of photosynthetic apparatus and its ability to restore membrane properties, oxygen evolution, and energy distribution upon rehydration were investigated in a resurrection plant, Haberlea rhodopensis. Plants growing under low irradiance in their natural habitat were desiccated to air-dry state at a similar light intensity [about 30 μol(photon) m^?2 s^?1] under optimal day/night (23/20°C) or high (38/30°C) temperature. Our results showed that HT alone reduced the photosynthetic activity and desiccation of plants at 38°C and it had more detrimental effect compared with desiccation at 23°C. The study on isolated thylakoids demonstrated increased distribution of excitation energy to PSI as a result of the HT treatment, which was enhanced upon the desiccation. It could be related to partial destacking of thylakoid membranes, which was confirmed by electron microscopy data. In addition, the surface charge density of thylakoid membranes isolated from plants desiccated at 38°C was higher in comparison with those at 23°C, which was in agreement with the decreased membrane stacking. Dehydration led to a decrease of amplitudes of oxygen yields and to a loss of the oscillation pattern. Following rehydration, the recovery of CO₂ assimilation and fluorescence properties were better when desiccation was performed at optimal temperature compared to high temperature. Rehydration resulted in partial recovery of the amplitudes of flash oxygen yields as well as of population of S₀ state in plants desiccated at 23°C. However, it was not observed in plants dehydrated at 38°C.     

Factors influencing the pathogenicity and development of Mattesia trogodermae infecting Trogoderma glabrum larvae

Factors that regulate development of Mattesia trogodermae in Trogoderma glabrum were defined, and their quantitative effects were determined. The rate of and the extent to which spore formation proceeds is strictly governed by temperature. More spores are produced at 30° than at 25°C and very low numbers of spores are formed when the incubation temperature is 35°C. When insects are incubated at 35°C for 1–10 days and transferred to 30°C for the remainder of the 30-day experiment, spore production capacity gradually declines with increasing time at 35°C. Two hypotheses are proposed for this phenomenon. Larval size also regulates the extent of spore production, larger larvae having greater potential for spore development. This is not influenced by dosage. Spore production in pupae and adults was always retarded.Dosage and environmental conditions which influence the virulence of M. trogodermae were investigated. These studies show that rates of mortality are higher at higher temperatures. Low doses of spores result in longer LT50's than do high doses at 25° and 30°C. No differences in rates of mortality were found between different doses at 35°C.     

Microsporidium goeldichironomi n. sp. and Microsporidium chironomi n. sp. (Microsporida: Apansporoblastina): Two new microsporidia from Florida chironomids

Two new species of Microsporida belonging to the genus Microsporidium are described. Microsporidium goeldichironomi n. sp. parasitizes the fat body of Goeldichironomus holoprasinus and Microsporidium chironomi n. sp. infects Chironomus attenuatus. Both microsporidia form uninucleate spores from rosette-shaped sporonts. M. goeldichironomi sporonts form 4, 6, 8, 10, 12, 16, and possibly more spores. Two shapes of spores are produced, oval, or slightly pyriform spores measuring 3.70 ± 0.09 × 2.49 ± 0.13 μm and pyriform spores measuring 3.74 ± 0.44 × 2.04 ± 0.17 μm. Electron micrographs show that both types of spores are uninucleate, have 8 to 11 polar filament coils and a lamellate polaroplast showing several distinct regions. M. chironomi spores are pyriform and are often joined at the posterior end in groups of two or four. They measure 4.12 ± 0.37 × 2.45 ± 0.26 μm. The spores are uninucleate, have six to seven polar filament coils and a lamellate polaroplast showing two distinct regions. Neither species can be transmitted per os and thus are assumed to be transovarially transmitted. No pansporoblastic membrane is present in either species.     

Viability of dry Trichoderma harzianum spores under storage

Spores of the potential biocontrol agent Trichoderma harzianum P1 were prepared without (M1) and with heat shock (40?°C for 90?min) after fermentation (M2), filtered into a paste and dried over silica gel. M1 and M2 exhibited high viability (55%) and similar initial trehalose contents (4.0 and 5.4%, respectively) after slow drying. No significant differences in viability were found between treatments during storage for 110 days under different temperatures, T (8, 33 and 42?°C) and water activities, a _w (0.03, 0.33 and 0.75). Viability of spores, after storage at a _w =0.03 were 100 and 70% for 8 and 33?°C, respectively. During storage, decrease in trehalose content and viability was faster at a _w =0.75 and 42?°C. Loss of viability was modeled by a first order kinetic model depending on 1/T and a _w . M2 (with heat shock) showed slightly higher trehalose contents than M1 which resulted in 100% viability after 52 days at 8?°C.     

Effect of Variation of Sporulation Time and Temperature on Thermostability of Bacillus cereus Spores

The optimum temperature for sporulation of a strain of Bacillus cereus was estimated at 30°–35°C, where the maximum yield of spores was obtained between 18 and 24 hours’ incubation. Sporulation was more rapid, but less extensive at 40°C and did not occur at all at 45°C. The heat resistance of the spores increased with the sporulation temperature from 20° to 40°C. The spores appear to be more susceptible to heat destruction in the early stage of spore production than after further incubation.     

Cold,freezing, and desiccation tolerance of the limpet Acmaea digitalis (Eschscholtz)

Cold, freezing, and desiccation tolerance were examined in the limpet, Acmaea digitalis (Eschscholtz). Fifty percent of the experimental population survived freezing at temperatures between ?10 ° and ?12 °C for at least 24 hr. In this temperature range, 60–80 % of the body water was frozen. The LD₅₀ for water loss by desiccation was 76.5% ± 1.3_δ. At 70–80% body water loss, solutes were concentrated between 350 and 500%. Some limpets failed to survive immersion in 450% seawater for 6 hr (100% scawater = salinity of 31‰), suggesting that much of the damage from freezing and desiccation was from an increased solute concentration. No glycerol could be detected in extracts of the foot and the visceral mass of A. digitalis during winter, confirming similar results in studies carried out on other intertidal molluscs.