Rate and diel periodicity of pheromone emission from female gypsy moths, (Lymantria dispar) determined with a glass-adsorption collection system

The rate of pheromone emission from wild and laboratory-reared gypsy moth (Lymantria dispar) (Lepidoptera: Lymantriidae) virgin females was determined with an all-glass aeration apparatus. This device incorporated a bed of 1-mm glass beads to extract entrained pheromone from the air flowing over the protruded gland. The temporal pattern of emission was established by monitoring individual females after eclosion for 24 consecutive 2-hr intervals.At a constant 24°C, both wild and laboratory females exhibited a similar diel periodicity of pheromone emission. The mean release rate increased after onset of photophase, generally attained maximal levels between 1600 and 2200 hr and declined during scotophase. Pheromone was released continuously and the mean daily emission increased with age for both wild and laboratory moths. The mean emission rate over the 48-hr monitoring interval was $\text{15.4 ng}\text{2 hr}$ for wild females vs $\text{14.7 ng}\text{2 hr}$ for laboratory moths. The peak emission from 2-day-old laboratory moths was ca.$\text{28 ng}\text{2 hr}$ compared with the ca.$\text{25 ng}\text{2 hr}$ released by their wild counterparts.The calling periodicity of laboratory females was determined at a constant 24°C and under a natural temperature rhythm. At 24°C, the proportion of females calling exceeded 45% throughout the diel period, whereas under the temperature rhythm, calling was virtually eliminated by temperatures below 15°C, indicating that temperature acts as an exogenous cue to modify the expression of the calling rhythm and thus potentially the periodicity of pheromone emission.     

The effects of photoperiod and temperature on calling behaviour and egg development of the bertha armyworm,Mamestra configurata (Lepidoptera: Noctuidae)

The effects of photoperiod and temperature on calling behaviour and the effects of temperature on the relationship between egg development and calling of virgin females of Mamestra configurata Walker were examined at 3 photoperiodic regimes and seven constant temperatures. Photoperiod affected the diel periodicity of calling and length of the daily calling period. The mean onset calling times were similar if the preceding scotophase(s) was 6–10 h long, but the onset of calling was delayed by 1–5 h if the preceding scotophase(s) was 12–18 h long. Long-term, constant temperature (from emergence until death) affected 4 aspects of calling: age at first calling, diel periodicity, length of the daily calling period, and percentage of females calling. Short-term temperature changes (during a single scotophase) affected calling in 3 ways: diel periodicity, length of the daily calling period, and percentage of females calling. The optimal temperature range for calling was, at least, 10–25°C; the upper limit and threshold were near 35 and < 5°C. The time of first calling was synchronized closely with the appearance of the first chorionated eggs in the ovaries at 10–35°C. Egg development and calling were adversely affected at 30 and 35°C. The physiological and ecological significance of the data are discussed.     

Influence of temperature,ethylene and cyanide on the occurrence of alternative respiration in mitochondria from iris bulbs

Mitochondria, isolated from iris (Iris hollandica cv. Ideal) bulbs that have been treated for early flowering with high temperatures (14 days at 35°C followed by 3 days at 40°C) or with ethylene (10–500 ppm), show an induction of alternative respiratory capacity and a rise in state III respiration. Mitochondria from untreated bulbs (stored at 30°C) do not have an alternative pathway capacity and state III respiration is low. Induction of the alternative respiration by ethylene is maximal after 24 h, while induction by high temperature (> 36°C) is much slower. In the temperature range from 36–40°C, the extent of the induced alternative respiratory capacity increases with higher temperatures. A temperature of 42°C is lethal within 5 days. Bulbs stored at 30°C and 35°C before 40°C treatment reach the same values for alternative respiratory capacity. A treatment of the bulbs with 2.2 mM HCN (30°C) leads to an induction of alternative respiration concomitant with a decrease in state III respiration, after a lag time of 2–3 days. A treatment of 5 days with 2.2 mM HCN or longer is lethal.     

The Timing of Calling and Mating in <Emphasis Type="Italic">Heterolocha jinyinhuaphaga</Emphasis> and the Influence of Environmental Determinants

We investigated the periodicities of calling and mating of Heterolocha jinyinhuaphaga (Lepidoptera: Geometridae) and the effects of temperature, relative humidity, and photoperiod on the timing of these behaviors. Females called on the first night after emergence, mainly during the second half of scotophase. The calling percentage increased on the second night and peaked on the third night, before decreasing. Mating had similar rhythms but peaked 1 h later than calling. As the moth aged, the mean onset times of calling and mating were advanced. Temperature, relative humidity, and photoperiod all affected the calling and mating. We found that 25°C was the most suitable temperature for calling and mating, whereas at higher or lower temperatures, the total calling percentage and the total mating percentage decreased, the onset time of calling was delayed, and mating duration decreased. Increased the relative humidity facilitated calling and mating. However, lengthened photoperiods inhibited the calling and mating.     

Calling behaviour under climate change: geographical and seasonal variation of calling temperatures in ectotherms

Calling behaviour is strongly temperature‐dependent and critical for sexual selection and reproduction in a variety of ectothermic taxa, including anuran amphibians, which are the most globally threatened vertebrates. However, few studies have explored how species respond to distinct thermal environments at time of displaying calling behaviour, and thus it is still unknown whether ongoing climate change might compromise the performance of calling activity in ectotherms. Here, we used new audio‐trapping techniques (automated sound recording and detection systems) between 2006 and 2009 to examine annual calling temperatures of five temperate anurans and their patterns of geographical and seasonal variation at the thermal extremes of species ranges, providing insights into the thermal breadths of calling activity of species, and the mechanisms that enable ectotherms to adjust to changing thermal environments. All species showed wide thermal breadths during calling behaviour (above 15 °C) and increases in calling temperatures in extremely warm populations and seasons. Thereby, calling temperatures differed both geographically and seasonally, both in terrestrial and aquatic species, and were 8–22 °C below the specific upper critical thermal limits (CT_max) and strongly associated with the potential temperatures of each thermal environment (operative temperatures during the potential period of breeding). This suggests that calling behaviour in ectotherms may take place at population‐specific thermal ranges, diverging when species are subjected to distinct thermal environments, and might imply plasticity of thermal adjustment mechanisms (seasonal and developmental acclimation) that supply species with means of coping with climate change. Furthermore, the thermal thresholds of calling at the onset of the breeding season were dissimilar between conspecific populations, suggesting that other factors besides temperature are needed to trigger the onset of reproduction. Our findings imply that global warming would not directly inhibit calling behaviour in the study species, although might affect other temperature‐dependent features of their acoustic communication system.     

Development ofDiatraea Saccharalis [Lep.: Pyralidae] at constant temperatures

At constant temperatures between 15.6 and 32°C the incubation time of eggs ofDiatraea saccharalis (F.) was reduced by each increase in temperature. At 34°C the time decreased. Highest (98.6%) and lowest (9.9%) egg hatch occurred at 26 and 34°C, respectively. Larvae completed development at temperatures ranging from 22 to 34°C; however, only 4.4% of the larvae pupated at 34°C. Duration of the larval stage at 30°C (♂=18.1 days; ♀=19.1 days) was ca. 14 days shorter than at 22°C. Maximum rate of development in the pupal stage occurred at 28°C (ca. 6.8 days), and a higher temperature increased developmental time and mortality. Adult longevity and egg production generally were reduced with increasing temperatures and egg production was highest at 24°C (729.8 eggs/ moth). As many as 7 larval stages occurred; but most larvae completed development in 5 stages, and none completed development in less than 5 stages. The female larval stage was ca. 1 day longer than that of males, and this difference occurred primarily in the 5th stage.     

Effects of temperature on infection of French bean leaves (Phaseolus vulgaris L.) by lucerne mosaic virus

The effect of temperature on the number of lesions and the time of their appearance was studied by inoculating French bean leaves (Phaseolus vulgaris L. cv. Perli?ka) with lucerne mosaic virus either 24 or 48 h before or, 24 or 48 h after they were exposed to various temperatures. The temperatures tested were 23, 25, 27, 30, 33 and 36° C. Before and after such exposures the plants were kept in a constant temperature of 25° C. By increasing the temperature before inoculation the number of lesions increased in comparison with the control. The optimal temperature for the maximum number of lesions is between 27° and 30° C. There is no significant difference between those experiments when the exposure time was 24 h or 48 h before inoculation. The same temperatures applied for 24 or 48 h after inoculation have a decreasing effect upon the number of lesions formed by LMV on French bean leaves. The decrease is 30 to 75%. In this case the first necrotic local lesions appeared 42 h after inoculation when exposed to higher temperatures above 27° C for 24 h, and 60 h after inoculation when exposed to these temperatures for 48 h. The shape of lesions varied a little in both cases as the pictures show.     

Adaptive responses of embryos and larvae of the heart-shaped sea urchin <Emphasis Type="Italic">Echinocardium cordatum</Emphasis> to temperature and salinity changes

The combined effects of temperature (8, 12, 14, 17, 20, 22 and 25°C) and a salinity decrease from 36 to 12‰ on the development of the sea urchin Echinocardium cordatum (Pennant) were studied. Embryonic development proved to be the process most vulnerable to a salinity decrease. It was completed successfully at 8–20°C within a narrow salinity range of 36–28‰ Larvae at the most resistant stage, the blastula, survived at 12–22°C and a salinity of 36–18‰. Larvae at the most sensitive stage, pluteus I with the first pair of arms, died even in a favorable environment, a temperature of 17–20°C and a salinity of 34–28‰. That may be related to qualitative alterations during skeleton formation and to transition to phytoplankton feeding. The resistance of larvae to variations in environmental factors gradually increased in the pluteus II and III stages; however, it significantly decreased before the settling of the larvae. Larvae that were 37 days old survived at a temperature of 14–20°C within a salinity range of 36–22‰ and at 22 and 25°C, they survived at a salinity of 36–24‰; however, all the larvae became abnormal at 25°C. The larvae settled earlier on sand inhabited by adult individuals of E. cordatum than on sand from other locations, and they settled faster at 20–25°C, than at 14 and 17°C. The juveniles, if lacking an opportunity to burrow in the sand, died within 14 days after settling.     

Calling behaviour of the potato aphid Macrosiphum euphorbiae oviparae under laboratory and field conditions

Abstract.  1. The calling behaviour of virgin oviparae of the potato aphid Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) was studied at three different constant temperatures under laboratory conditions. The mean age of calling for the first time decreased with a decrease in temperature from 2.9 days at 20 °C to 2.1 days at 10 °C. At all temperature regimes, the mean onset time of calling advanced from about 5 to 3 h after the onset of the photophase, and the mean time spent calling increased by > 4 h over the 8 days.
2. Cohorts of oviparae were also observed at two different periods in late summer–early autumn in the field, to examine the effects of fluctuating abiotic conditions (temperatures, wind velocity, rain) and age on calling behaviour. As under constant laboratory conditions, the mean age of calling for the first time declined with declining temperature, from 3.7 days in early September to 1.6 days at the end of September. Age-related changes in the mean onset time of calling and the mean time spent calling were much less evident under field conditions, due to the inhibitory effects of low temperatures, high winds, and rain on female calling activity.
3. The results are discussed within the context of reproductive success and address a previously proposed hypothesis suggesting that species-specific calling windows may serve as a reproductive isolating mechanism for sympatric aphid species.     

Fatty acids profile and temperature in the cultured marine diatom Odontella aurita

The diatom Odontella aurita has now been industrially cultured and commercialized as a dietary supplement rich in omega-3 fatty acids for several years. In this study, we investigated the effect of three temperatures (8, 16, and 24 °C) on the growth and fatty acid composition of cells harvested during the exponential and stationary growth phases. These temperatures were selected on the basis of photosynthesis responses previously obtained at different temperatures using a modulated fluorometer. Our results confirm that both growth and lipid composition were sensitive to culture temperature. Growth was reduced when O. aurita was cultured at low temperature (8 °C) compared to when it was cultured at high temperatures (16 and 24 °C), but the proportion of polyunsaturated fatty acids (PUFAs, 20:5 n-3 and 22:6 n-3) increased while the level of saturated fatty acids (SFAs, 14:0 and 16:0) decreased in the cells harvested during both the exponential and stationary growth phases. On the other hand, the cells grown at 24 °C displayed a marked decrease in PUFA and an increase in SFA levels. Harvesting time is also a critical parameter in achieving optimum n-3 PUFA productivity during batch cultivation. Indeed, changes in fatty acid composition with growth phase seem to be dependent on the culture temperature, with the most marked effects being observed at 24 °C. PUFA levels (i.e., levels of 20:5 n-3 and 22:6 n-3) increased during the stationary growth phase, while the proportion of SFAs and monounsaturated fatty acids (MUFAs) fell with time. As this species is currently grown in outdoor ponds with seasonal temperature variations (minimal and maximal average temperatures in winter and summer, from 3 to 9 °C and from 13 to 26 °C, respectively), this factor can be expected to have a strong influence on the fatty acid content and composition of the algal biomass harvested and commercialized.     

The effects of mating,exogenous juvenile hormone and a juvenile hormone analogue on pheromone titre,calling and oviposition in the omnivorous leafroller moth (Platynota stultana)

Mating in Platynota stultana resulted in the termination of calling, the gradual reduction of pheromone in the pheromone glands to non-detectable levels (<0.1 ng/♀) within 14 h, and oviposition of the first batch of eggs 20–24 h after copulation. Decapitation of virgin females resulted in a similar decline in pheromone titre, and also eliminated oviposition and calling. Pheromone production appears to be controlled via the head. Mating probably terminates neural or hormonal input required for pheromone production and/or removes neural or hormonal inhibition of pheromone degradation. A juvenile hormone analogue (ZR-512) and juvenile hormones I, II and III applied exogenously to virgin females elicited oviposition comparable to mated females and terminated calling within 48 h. The juvenile hormone analogue also appeared to block pheromone production in virgin females. These results suggest that juvenile hormone may be involved in the switch from virgin to mated behaviour in this species.     

Synchronisation of egg hatching of brown hairstreak (Thecla betulae) and budburst of blackthorn (Prunus spinosa) in a warmer future

Synchronisation of the phenology of insect herbivores and their larval food plant is essential for the herbivores’ fitness. The monophagous brown hairstreak (Thecla betulae) lays its eggs during summer, hibernates as an egg, and hatches in April or May in the Netherlands. Its main larval food plant blackthorn (Prunus spinosa) flowers in early spring, just before the leaves appear. As soon as the Blackthorn opens its buds, and this varies with spring temperatures, food becomes available for the brown hairstreak. However, the suitability of the leaves as food for the young caterpillars is expected to decrease rapidly. Therefore, the timing of egg hatch is an important factor for larval growth. This study evaluates food availability for brown hairstreak at different temperatures. Egg hatch and budburst were monitored from 2004 to 2008 at different sites in the Netherlands. Results showed ample food availability at all monitored temperatures and sites but the degree of synchrony varied strongly with spring temperatures. To further study the effect of temperature on synchronisation, an experiment using normal temperatures of a reference year (T) and temperatures of T + 5°C was carried out in climate chambers. At T + 5°C, both budburst and egg hatch took place about 20 days earlier and thus, on average, elevated temperature did not affect synchrony. However, the total period of budburst was 11 days longer, whereas the period of egg hatching was 3 days shorter. The implications for larval growth by the brown hairstreak under a warmer climate are considered.     

Pathogenesis and midgut histopathology of Bacillus thuringiensis in Simulium vittatum (Diptera: Simuliidae)

The pathogenesis and midgut histopathology which resulted when larvae of the blackfly, Simulium vittatum, were exposed to Bacillus thuringiensis at various temperatures and periods of exposure were investigated. The onset of mortality was studied at 10°, 15°, 19°, and 24°C. For each 4–5°C increase in temperature above 15°C, the onset of mortality was shortened by 24 hr. Exposures as brief as 15 min to 10 ppm of a whole spore preparation resulted in an average mortality of 29% in late-instar larvae. Mortality increased sharply for exposures up to 3 hr, approaching a maximum of 80%.The gross signs of disease included cessation of feeding and tetany with brachytosis. The tissue most affected was the midgut epithelium in the regions of the gastric caeca and posterior stomach. The formation of cytoplasmic vacuoles followed by cell lysis and/or sloughing were very apparent in moribund larvae. Death resulted without bacteremia.     

Development rate,number of mature oocytes at emergence and adult size ofEncarsia tricolor at constant and variable temperatures

The duration of the development of the aphelinidEncarsia tricolor Föerster (a parasitoid of the aleyrodidTrialeurodes vaporariorum (Westwood), adult size and number of mature oocytes at emergence were determined under constant and variable temperature regimes. Females developed successfully from 14 to 32°C, but a 100% of pupal mortality was observed at 34°C. Males developed successfully from 16 to 28°C and they developed faster than females. Female and male, egg to adult development at constant temperatures ranged from 51.1 (14°C) to 14.3 (28°C) days and from 32.6 (16°C) to 11.8 (28°C) days, respectively. Predictions of the rate of development at variable temperatures were more accurate when made from 2nd and 3rd degree polynomials than from linear regressions. The number of mature oocytes at emergence ranged from 0.1 (30°C) to 2.2 (20°C). FemaleE. tricolor attained the greatest size at 20–24°C. The comparison with literature data shows thatE. tricolor develops faster thanT. vaporariorum at temperatures above 15°C.     

The in vitro effect of temperature on motility and antioxidant response of common carp Cyprinus carpio spermatozoa

The effect of temperature on Cyprinus carpio spermatozoa in vitro was investigated with spermatozoa activated at 4, 14, and 24 °C. At 30 s post-activation, motility rate was significantly higher at 4 °C compared to 14 and 24 °C, whereas highest swimming velocity was observed at 14 °C. The thiobarbituric acid-reactive substance (TBARS) content was significantly higher at 14 °C and 24 °C than at 4 °C in motile spermatozoa. No significant differences in catalase and superoxide dismutase activity relative to temperature were observed. This study provides new information regarding effect of temperature on lipid peroxidation intensity and spermatozoon motility parameters in carp. The elevation of TBARS seen at higher temperatures could be due to inadequate capacity of antioxidant enzymes to protect the cell against the detrimental effects of oxidative stress induced by higher temperatures.     

Temperature dependent defence of <Emphasis Type="Italic">Nicotiana tabacum</Emphasis> against <Emphasis Type="Italic">Cucumber mosaic</Emphasis> virus and recovery occurs with the formation of dark green islands

Temperature is an important environmental factor controlling plant growth, development, and immune response. However, the role of temperature in plant disease resistance is still elusive. In the present study, the potential effects of temperature on the interaction between Nicotiana tabacum and Cucumber mosaic virus (CMV) were investigated. Our results indicated that N. tabacum plants displayed severe symptoms at early stage of post inoculation at high temperature (HT, 28°C), associated with higher viral replication level, more serious stress damages. By contrast, low temperature (LT, 18°C) effectively delayed the replication of CMV compared with elevated temperatures. Additionally, quantitative real-time PCR analyses revealed that lower temperatures (≤ 24°C) promote salicylic acid (SA) dependent responses, whereas higher temperatures (> 24°C) activate the genes expression of jasmonic acid (JA) pathway. Interestingly, the dark green islands (DGIs) appeared much earlier in CMV-inoculated plants grown at HT compared with those at LT and the accumulation of virus small interfering RNAs in plants were significantly up-regulated under elevated temperatures at early stage of post inoculation. Taken together, these results indicated that temperature changes had important effects on plant defence response, and different temperatures could induce different immune pathways of N. tabacum against CMV infection.     

Effects of salinity and cyclic temperature on survival of two sympatric species of grass shrimp (Palaemonetes), and their relationship to natural distributions

Survival and respiration of the grass shrimp Palaemonetes pugio Holthuis and P. vulgaris (Say) from the Newport River estuary were measured after exposure to cyclic and constant winter temperatures, to rapid decreases in temperature, and to various temperature-salinity combinations. Both species were subjected to nine temperature-salinity combinations including temperature regimes of cyclic 7–13°C, constant 7° and 10°C, and salinities of 5, 20, and 35%.. Based on the laboratory and field results, the differences in physiological tolerance to winter temperatures and salinities were examined in relation to habitat partitioning by these sympatric species.Survival after continuous exposure to cyclic temperature regimes at medium to high salinities was similar to that observed for comparable constant temperatures; however, at low salinities mortality was significantly lower under the cyclic regime than under either constant regime. This suggests that cyclic temperatures may be detrimental in combination with some other stress. A rapid, transient decrease in temperature from either 7° or 10°C to 2°C had no measurable effect on survival or rate of oxygen consumption at any temperature-salinity acclimation. Neither salinity (except in areas intermittently subjected to salinities below 3 %.) nor winter temperatures appear to affect habitat partitioning in grass shrimp.     

Endogenous and exogenous factors affecting periodicities of female calling and male sex pheromone response in Grapholitha molesta (Busck)

In Grapholitha molesta periodicities of both female calling and male response to sex pheromone by wing fanning while walking were determined in part by circadian rhythms. The lights-on photoperiodic cue was at least partly responsible for setting the phase of the female calling rhythm. Absolute temperature levels and not necessarily a decrease in temperature modified the timing of calling; there were both high and low thresholds of temperature and, at particular photoperiod times, a temperature range optimal for calling. When the previous performance of calling was prevented by subthreshold temperatures, calling during the next period commenced earlier if temperatures were favourable. Thus, the previous performance of calling may establish a refractory period, or temperature decrease may act as a cue resetting the phase of the calling rhythm. The ability to use both an endogenous clock and exogenous temperature cues to synchronize sexual activity appears adaptive for a temperate zone insect whose multiple generations are exposed to both long periods of favourable climatic conditions in summer and harsh, unpredictable conditions in spring or fall.     

Differential responses of Arabidopsis ecotypes to cold, chilling and freezing temperatures

Arabidopsis plants show an increase in freezing tolerance in response to exposure to low nonfreezing temperatures, a phenomenon known as cold acclimation. In the present study, we evaluated the physiological and morphological responses of various Arabidopsis ecotypes to continuous growth under chilling (14°C) and cold (6°C) temperatures and evaluated their basal freezing tolerance levels. Seedlings of Arabidopsis plants were extremely sensitive to low growth temperatures: the hypocotyls and petioles were much longer and the angles of the second pair of true leaves were much greater in plants grown at 14°C than in those grown at 22°C, whereas just intermediate responses were observed under the cold temperature of 6°C. Flowering time was also markedly delayed at low growth temperatures and, interestingly, lower growth temperatures were accompanied by longer inflorescences. Other marked responses to low temperatures were changes in pigmentation, which appeared to be both ecotype specific and temperature dependent and resulted in various visual phenotypes such as chlorosis, necrosis or enhanced accumulation of anthocyanins. The observed decreases in chlorophyll contents and accumulation of anthocyanins were much more prominent in plants grown at 6°C than in those grown at 14°C. Among the various ecotypes tested, Mt‐0 plants markedly accumulated the highest levels of anthocyanins upon growth at 6°C. Freezing tolerance examination revealed that among 10 ecotypes tested, only C24 plants were significantly more sensitive to subzero temperatures. In conclusion, Arabidopsis ecotypes responded differentially to cold (6°C), chilling (14°C) and freezing temperatures, with specific ecotypes being more sensitive in particular traits to each low temperature.     

Torpor-associated fluctuations in surfactant activity in Gould’s wattled bat

The primary function of pulmonary surfactant is to reduce the surface tension (ST) created at the air–liquid interface in the lung. Surfactant is a complex mixture of lipids and proteins and its function is influenced by physiological parameters such as metabolic rate, body temperature and breathing. In the microchiropteran bat Chalinolobus gouldii these parameters fluctuate throughout a 24 h period. Here we examine the surface activity of surfactant from warm–active and torpid bats at both 24°C and 37°C to establish whether alterations in surfactant composition correlate with changes in surface activity. Bats were housed in a specially constructed bat room at Adelaide University, at 24°C and on a 8:16 h light:dark cycle. Surfactant was collected from bats sampled during torpor (25<T_b<28°C), and while active (T_b>35°C). Alterations in the lipid composition of surfactant occur with changes in the activity cycle. Most notable is an increase in surfactant cholesterol (Chol) with decreases in body temperature [Codd et al., Physiol. Biochem. Zool. 73 (2000) 605–612]. Surfactant from active bats was more surface active at higher temperatures, indicated by lower ST_min and less film area compression required to reach ST_min at 37°C than at 24°C. Conversely, surfactant from torpid bats was more active at lower temperatures, indicated by lower ST_min and less area compression required to reach ST_min at 24°C than at 37°C. Alterations in the Chol content of bat surfactant appear to be crucial to allow it to achieve low STs during torpor.