Effects of changes in temperature and saturation deficit on the survival of eggs of Trichostrongylus colubriformis (Nematoda: Trichostrongylidae)

and 1972. Effects of changes in temperature and saturation deficit on the survival of eggs of Trichostrongylus colubriformis (Nematoda: Trichostrongylidae) International Journal for Parasitology, 2: 439–447. In conformity with a hypothesis relating to survival of the developing T. colubriformis egg exposed to desiccation, samples of eggs initially at the early blastomere stage of development showed decreased mortality during development with increasing temperature of incubation up to 25°C, for approximately constant rates of evaporation. At 30°C there was a higher percentage mortality for fixed evaporation rate than at 20° or 25°C. It is suggested that at 30°C there may be an abrupt increase in the initial rate of water loss from the developing embryo resulting from a change in the permeability to water of the lipid layer of the egg envelope.

Fully embryonated T. colubriformis eggs were obtained by incubation at 20°C in the presence of a moderate saturation deficit during development. When such eggs were transferred to 30° and 40°C there was no mortality at the higher temperature, providing that the saturation deficit was substantially increased. A hypothesis proposed for survival at high temperature is based on analogy with water loss through the arthropod cuticle and is attributed to a decrease in permeability of the protein-chitin layer of the egg envelope under conditions of high evaporation rate, even though permeability of the lipid layer might be increased by high temperature.     

Survival of six species of African ticks in relation to saturation deficits

The survival of unfed males and females of six species of African ticks was monitored at five different saturation deficits at constant temperature (25°C). The survivorship curves for each species comprised a pre-mortality period, prior to when ticks started to die and a mortality period corresponding to a rapid increase in the mortality rate. Longevity was defined as pre-mortality plus mortality. A negative correlation between the longevity of the ticks and the saturation deficits was found with ticks surviving longer at lower deficits. The survival of males and females was similar. At low saturation deficits (2–4 mmHg) Amblyomma hebraeum survived the longest periods (74 weeks). Some correlation was found between the tick survival under dehydrating conditions and habitat associations. Rhipicephalus appendiculatus and Haemaphysalis leachii, the most mesic in distribution, had the shortest longevity (21 and 13 weeks, respectively) at high saturation deficits (7–21 mmHg). Hyalomma marginatum rufipes, the most xerophilic in distribution, had the longest survival (39.3±10.5 weeks) at high saturation deficits. Other factors apart from the adult survival should be taken into account when accounting for the tick distribution, in particular the tolerance of earlier developmental stages to desiccation.     

Effects of temperature on the development and survival of an endangered butterfly, Shijimiaeoides divinus barine (Leech) (Lepidoptera: Lycaenidae)

The effects of temperature on the development and survival of Shijimiaeoides divinus barine were examined in the laboratory in 2008. The eggs and larvae were reared at temperatures of 15, 17.5, 20, 25, 30 and 35°C with a long-day photoperiod of 16 h light : 8 h dark (16L : 8D). The highest hatchability of eggs was 88.0% at 20°C, but hatchability at high temperatures of 30 and 35°C was 30 and 0%, respectively. The lowest and highest survival rates from the first to third instar were 18.8% at 15°C and 76.9% at 20°C. Few deaths were observed after the fourth instar. The shortest developmental periods of the eggs and larvae were 4.0 and 15.8 days at 30°C, and the durations of the egg and larval stages increased significantly as the temperature decreased. The developmental zero and thermal constants were 9.6°C and 82.6 degree–days for the egg stage, and 10.7°C and 306.8 degree–days for the larval stage. The developmental period of the natural population of S. divinus barine in Azumino City, Nagano Prefecture was calculated using the developmental zero, thermal constants and Azumino City temperature data.     

On the water balance ofPhytoseiulus persimilis A.-H. and its ecological significance

The net water vapour exchange ofPhytoseiulus persimilis A.-H. is described. Water loss by transpiration increases progressively with ambient temperature. The transpiration rate is directly proportional to the saturation deficit of the air (15 to 30° C) and at constant temperature linearly dependent on the water vapour activity: m_T=–0.81 a_v+0.91 (for a_v 0.0 to 0.85 at 20°C). Phytoseiulus persimilis is able to absorb water vapour from the unsaturated atmosphere. This occurs above a certain threshold (critical equilibrium activity, CEA), which is a_v=0.9 at 15 to 25°C and increases to a_v=0.935 at 30°C.The environmental humidity conditions influencingP. persimilis on the leaf surface are described. The diurnal water vapour profile within the laminar layer at the leaf surface includes periods with water vapour values high enough for these mites to utilize their water vapour sorption capability and to restore a previously-suffered water deficit. In addition,P. persimilis shows a positive hygrotactic behaviour when in a state of water deficit.The survival time of starvingP. persimilis is at least doubled when a possibility to absorb water vapour is available. The water balance at limited food resources is discussed. With a food supply (one prey mite, containing about 5.5 g water) every 3 days and a water vapour activity of a_v=0.76 (20°C), water balance is achieved and the survival time is maximal (approximately 120 days).     

THE EFFECTS OF TEMPERATURE AND HUMIDITY ON THE RATE OF DEVELOPMENT AND THE MORTALITY OF TRIBOLIUM CONFUSUM DUVAL (COLEOPTERA, TENEBRIONIDAE)

The speed of development and the developmental mortality of Tribolium confusum were studied over a series of constant temperatures between 15° and 40° C. at 10, 30, 70 and 90% R.H. using wheatfeed as food.
Eggs did not hatch at 15° or 40° C. at any humidity. At 37.5° C. about 60% of eggs hatched and at all other conditions about 90% hatched. The effect of temperature on the duration of the egg period is shown graphically, the shortest period being at 35° C. Humidity does not affect the egg period.
Larvae failed to develop to pupae at 17.5° C., at 10% R.H. at 20° C, and at 10 and 90% R.H. at 37.5° C. The rate of larval development was affected by both temperature and humidity being quickest at the higher humidities and at about 32.5° C. Larval mortality was less than 16% except at 37.5° C., at 10% R.H. or less, and at 20°C., 90% R.H.
The duration of the pupal period was not affected by humidity and was shortest at 37.5°C. The total developmental period is compared with that of T. castaneum over the range of temperature and humidity conditions in which both species can grow. The optimum for developmental speed and the maximum and the minimum temperatures at which development is possible were all about 2.5°C. lower for T. confusum than for T. castaneum. The developmental periods for the two species were equal at temperatures between 23 and 27°C., depending on humidity. At lower temperatures, T. confusum developed the more quickly and at higher temperatures the more slowly.     

Laboratory estimation of degree-day developmental requirements of Phlebotomus papatasi (Diptera: Psychodidae).

Cutaneous leishmaniasis is one of the most important vector-borne endemic diseases in Turkey. The main objective of this study was to evaluate the influence of temperature on the developmental rates of one important vector of leishmaniasis, Phlebotomus papatasi (Scopoli, 1786) (Diptera: Psychodidae). Eggs from laboratory-reared colonies of Phlebotomus papatasi were exposed to six constant temperature regimes from 15 to 32 degrees C with a daylength of 14 h and relative humidity of 65-75%. No adult emergence was observed at 15 degrees C. Complete egg to adult development ranged from 27.89 +/- 1.88 days at 32 degrees C to 246.43 +/- 13.83 days at 18 degrees C. The developmental zero values were estimated to vary from 11.6 degrees C to 20.25 degrees C depending on life stages, and egg to adult development required 440.55 DD above 20.25 degrees C.     

Longevity and development of the egg-parasitoid,Cheiloneurus pyrillae [Hymenoptera: Encyrtidae] at different combinations of temperature and relative humidity

Out of the 2 important physical factors like temperature and relative humidity, the former plays significant role in affecting the survival of adults and development of immature stages ofCheiloneurus pyrillae Mani which is an important egg parasitoid of the sugarcane leaf hopper (Pyrilla perpusilla Walker) in India. Average longevity of males and females of this parasitoid decreased from 2.47 to 0.81 days and from 4.95 to 0.84 days, respectively when the test temperature was increased from 15 to 35±1.5°C. Similarly, its mean developmental period was found to reduce from a maximum of 45.87 to a minimum of 10.12 days when the rearing temperature was increased from 15 to 30±1.5°C. The parasitoid could not be reared at or above 32.5±1.5°C because its immature stages failed to withstand this temperature. These informations will be helpful in maintaining the mass culture ofC. pyrillae in the laboratory.     

Effects of temperature on the immature development of the stone leek leafminer Liriomyza chinensis (Diptera: Agromyzidae)

The effect of nine constant temperatures (15, 17.5, 20, 22.5, 25, 27.5 30, 32.5, and 35 degrees C) on the development of the stone leek leafminer, Liriomyza chinensis (Kato), on Japanese bunching onion, Allium fistulosum L., was studied in the laboratory. Developmental times for immature stages were inversely proportional to temperature between 15 and 30 degrees C but increased at 32.5 degrees C. Total developmental times from egg to adult emergence decreased from 69.6 to 17.1 d for temperatures from 15 to 30 degrees C, with pupae requiring more time for development than the combined egg and larva stages. Both linear and nonlinear (Logan equation VI) models provided a reliable fit of development rates versus temperature for all immature stages. The lower developmental thresholds that were estimated from linear regression equations for the egg, first, second, and third instars, total larva, egg-larval, pupa, and total combined immature stages were 12.1, 10.6, 13.6, 8, 9.6, 11.3, 11.2, and 11.4 degrees C, respectively. The degree-day accumulation was calculated as 312.5 DD for development from egg to adult emergence. By fitting the nonlinear models to the data, the upper and optimal temperatures for egg, larva, pupa, and total immature stages were calculated as 37.8 and 31.7, 34.9 and 30.1, 35.8 and 30.6, and 35.0 and 30.9 degrees C, respectively. These data are useful for predicting population dynamics of L. chinensis under field conditions and determining the maximum proportion of susceptible individuals for facilitating improved timing of application of control measures.     

Effect of water temperature on the development, release and survival of the triactinomyxon stage of Myxobolus cerebralis in its oligochaete host.

The development of the triactinomyxon stage of Myxobolus cerebralis and release of mature spores from Tubifex tubifex were shown to be temperature dependent. In the present work, the effect of temperature over a range of 5-30 degrees C on the development and release of the triactinomyxon stages of M. cerebralis was studied. Infected T. tubifex stopped releasing triactinomyxon spores 4 days after transfer from 15 degrees C to 25 degrees C or 30 degrees C. Transmission electron microscopic examinations of the tubificids held at 25 degrees C and 30 degrees C for 3 days showed that all developmental stages degenerated and transformed to electron-dense clusters between the gut epithelial cells of T. tubifex. In contrast, tubificid worms held at 5 degrees C and 10 degrees C examined at the same time were heavily infected with many early developmental stages of triactinomyxon. At 15 degrees C, the optimal temperature for development, maturing and mature stages of the parasite were evident. Infected T. tubifex transferred from 15 degrees C to 20 degrees C stopped producing triactinomyxon spores after 15 days. However, 15 days at 20 degrees C was not sufficient to destroy all developmental stages of the parasite. When the tubificid worms were returned to 15 degrees C, the one-cell stages and the binucleate-cell stages resumed normal growth. It was also demonstrated that T. tubifex cured of infection by holding at 30 degrees C for 3 weeks and shifted to 15 degrees C could be re-infected with M. cerebralis spores. The waterborne triactinomyxon spores of M. cerebralis did not appear to be as short-lived as previously reported. More than 60% of experimentally produced waterborne triactinomyxon spores survived and maintained their infectivity for rainbow trout for 15 days at water temperatures up to 15 degrees C. In natural aquatic systems, the triactinomyxon spores may survive and keep their infectivity for periods even longer than 15 days.     

Threshold temperature and heat unit requirements for the development of the granary weevil,Sitophilus granarius (L.)

The objective of the present investigation was to determine the effects of temperature on the granary weevil, Sitophilus granarius L., in the laboratory so that forecasting models based on heat accumulation units could be developed for the pest. Development of S. granarius reared on wheat grains was studied at three constant temperatures (15, 20 and 25?°C) and relative humidity of 70?±?5%. The developmental time was significantly decreased with the increase in temperature. The developmental threshold temperatures estimated for egg, larva, pupa and from egg to adult were 7.79, 7.31, 14.08 and 9.97?°C, respectively. Based on these thresholds, the developmental stages, respectively, needed 92.75, 393.78, 45.04 and 562.36?day degrees to complete their development. Also, about nine generations were calculated for the pest per year under Assiut prevailing conditions. It seems that temperature of 25?°C is the most favourable developmental temperature.     

Temperature-dependent development and reproduction of the boll weevil (Coleoptera: Curculionidae)

Abstract Effects of temperature on development, survival, and fecundity of boll weevil, Anthonomus grandis grandis Boheman, were assessed at 10, 11, 12, 15,20,25,30,35,45, and 46 °C; 65% relative humidity; and a photoperiod of 13:11 (L: D) h. The mortality of boll weevil immature stages was 100% at 12°C and decreased to 36.4% as the temperature increased to 25°C. When the temperature increased from 30 °C to 45 °C, the mortality of weevils also increased from 50.1% to 100%. From 15°C to 35°C, the bollweevilpreimaginal development rate was linearly related to temperature. The average development time of total boll weevil immature lifestages decreased 3.6-fold and the preovipositional period decreased 3.3-fold when the temperature was increased from 15°C to 30°C. The lower threshold for development was estimated at 10.9, 6.6, 7.0, and 9.0 °C for eggs, larval, pupal, and total immature stages, respectively, with total thermal time requirement to complete immature stages of 281.8 DD (degree day) (15°C) and 247.8 DD (35 °C). At 1LC and 46°C, weevil females did not oviposit. Longevity of adult females decreased 4.6-fold with increasing temperatures from 15°C to 35°C. Fecundity increased with increasing temperatures up to 30°C and significantly decreased thereafter. These findings will be useful in creating a temperature-based degree-day model for predicting the occurrence of key life stages in the field. An accurate predictor of a pest's development can be very important in determining sampling protocols, timing insecticide applications, or implementing an integrated pest management control strategy targeting susceptible life stages.     

Effect of temperature on development rate and fecundity of apterous Aphis gossypii Glover (Hom., Aphididae) reared on Gossypium hirsutum L.

The developmental time, survival and reproduction of the cotton aphid, Aphis gossypii Glover (Hom., Aphididae), were evaluated on detached cotton leaves at five constant and two alternating temperatures (15, 20, 25, 30, 35, 25/30, and 30/35°C). The developmental periods of the immature stages ranged from 12.0 days at 15°C to 4.5 days at 30°C. A constant temperature of 35°C was lethal to the immature stages of A. gossypii. The lower developmental threshold for the cotton aphid was estimated at 6.2°C and it required 108.9 degree-days for a first instar to become adult. The average longevity of adult females was reduced from 39.7 days at 15°C to 12.6 days at 30/35°C. The average reproduction rate per female was 51.5 at 25/30°C and 20.9 at 30/35°C. Mean generation time of the population ranged from 10.4 days at 30°C to 24.5 days at 15°C. The largest per capita growth rate ( r _m = 0.413) occurred at 30°C, the smallest at 15°C ( r _m = 0.177). It was evident that temperatures over 30°C prolonged development, increased the mortality of the immature stages, shortened adult longevity, and reduced fecundity. The optimal range of temperature for population growth of A. gossypii on cotton was 25/30–30°C.     

Relationships between temperature, development and survival of different life stages of the tomato fruit fly, Neoceratitis cyanescens

The development and survival of female Neoceratitis cyanescens (Bezzi) (Diptera: Tephritidae) from egg to complete ovarian maturation were studied in the laboratory at five different constant temperatures: 15, 20, 25, 30, and 35 °C. The aim of this study was to get information on the influence of temperature on pre-mature stages, as a prerequisite to optimise rearing procedures and to understand temporal and geographical patterns of fruit fly occurrence. The developmental rate of the different life stages increased linearly with increasing temperatures up to 30 °C. The fastest development of pre-mature stages was recorded at 30 °C (22±1 days) and the slowest at 15 °C (98±3 days). The day-degrees requirements (K) to complete total development were 432.6 day-degrees. Lower temperature thresholds were 11.4, 11.9, 10.0, and 11.1 °C for egg, larval, pupal stages and ovarian maturation, respectively. The number of adults obtained from an initial batch of 100 eggs reached a maximum (64) at 25 °C. At 35 °C, no adults emerged. Larval developmental time was significantly shorter in green tomato fruits than in potato tubers at 15, 20, and 25 °C. Mortality rate of larvae was higher in green tomato fruits than in potato tubers at 25 and 30 °C.     

A laboratory study of the feeding of Mesostoma lingua (Schmidt) (Turbellaria: Neorhabdocoela) on Daphnia magna Straus at four different temperatures

Mesostoma lingua eats 0.8 Daphnia magna at 15 °C, and 2.04 at 30 °C. Below 0.5 Daphnia per day (D d^–1) hunger occurs, at any temperature, and mortality increases sharply. The functional response curve appears to be linear, but saturation was not fully reached at 5 D d^–1, the highest food level applied in the present study. All food regimes (above hunger level) and temperature regimes differed significantly from each other; factor interactions were of increasing importance at higher temperatures.Longevity, above hunger level, decreased with temperature. Peak longevity at low temperature may be weakly associated with relatively low food levels.     

Thermal preferences of subtropical Aedes aegypti and temperate Ae. japonicus mosquitoes

Temperature is an important determinant affecting the capacity of disease vectors like mosquitoes (Culicidae) to transmit disease agents. Although the impact of temperature on vector-borne disease dynamics has been studied intensively, the actual temperature encountered by the vector in a heterogeneous landscape is rarely taken into account. If disease vectors have temperature preferences and therefore select specific microhabitats, this would substantially influence key life history traits that determine transmission intensity. The thermal preferences of subtropical Aedes aegypti and temperate Ae. japonicus mosquitoes were investigated in a temperature gradient set-up consisting of a Plexiglas box on top of an aluminium plate on two thermal regulators. Blood-fed (one day after feeding) and unfed (non-blood-fed) mosquitoes were released in small (15–20 °C, 20–25 °C, 25–30 °C) and large (15–30 °C, 30–45 °C) temperature gradients to assess their thermal preferences after 15 min. Additionally, the effect of humidity was investigated in a two-choice chamber setup. Both mosquito species avoided higher temperatures, pronouncedly dangerously high temperatures in the 30–45 °C gradient. At lower temperatures, blood-fed mosquitoes preferred the cooler sides of the 20–25 °C and 25–30 °C gradient, which were all below their rearing temperature. In the lowest gradient of 15–20 °C, no preferences were found. The thermal preference of unfed mosquitoes was similar to that of the blood-fed mosquitoes. No humidity preference or effect of humidity on temperature preferences was observed within the tested range (40–90%). The set-up allows for assessing the thermal preference of mosquitoes under controlled conditions. The observed preference of mosquitoes for cooler temperatures would increase their longevity and slow down pathogen development. If similar microhabitat selection is observed in the field, vector borne disease models should be adjusted accordingly.     

Differentiation of two locally sympatric Protopolystoma (Monogenea: Polystomatidae) species by temperature-dependent larval development and survival

The developmental response of egg stages to different environmental temperature regimes was studied in Protopolystoma xenopodis and Protopolystoma orientalis (Monogenea: Polystomatidae) isolates from southern Africa. Eggs failed to develop at 10 degrees C, whilst at 15 degrees C only P. xenopodis completed larval development, hatching 49--88 days post-collection. Respective hatching windows were 26--34 (P. xenopodis) and 37--49 (P. orientalis) days at 20 degrees C, and 18--26 and 27--37 days at 25 degrees C. Continuous maintenance at 30 degrees C was lethal for eggs of both species. There were no consistent interspecific differences in the response of egg stages to low and high temperature shocks during early embryonic development.     

THE EFFECT OF TEMPERATURE AND HUMIDITY ON THE RATE OF DEVELOPMENT AND MORTALITY OF TRIBOLIUM CASTANEUM (HERBST) (COLEOPTERA, TENEBRIONIDAE)

The speed of development and the developmental mortality of Tribolium castaneum were studied over a series of temperatures between 15 and 40°C. at 10, 30, 70 and 90% R.H. using wheatfeed as food.
Eggs did not hatch at any humidity at 17·5°C. or less, nor at 10% R.H. at 40°C. At all other conditions about 80% of eggs hatched. Humidity does not affect the duration of the egg period. The effect of temperature on the egg period is shown graphically, the shortest period occurring at 37·5°C.
Larvae fail to develop into normal adults at 20°C. and also fail at 90 and 30% R.H. at 40°C. At 20°C. and 70% R.H. pupae may be formed but they do not become normal adults. The rate of larval development is affected by both temperature and humidity. Development is quickest at the highest humidity used at any temperature and at 35°C. for each humidity. Larval mortality is less than 20% except at 40°C. and at combinations of low humidity and low temperature. The results correspond with published results using similar foodstuffs.
Groundnuts were used as a food in a series of experiments at 30°C. and another series at 70% R.H. Larvae on this food were much more susceptible to the effects of humidity and were unable to develop at 20 or 40°C. at 70% R.H. In all conditions development was slower and mortality higher than on wheatfeed.
The pupal period is not affected by humidity and is shortest at 37·5°C.
The conditions in which Park found that cultures of T. castaneum became extinct, 24°C. and 30% R.H., lie inside the zone in which development is possible. The possible causes for this discrepancy are discussed.     

Biological parameters of Thripobius semiluteus Bouček (Hym., Eulophidae), a larval endoparasitoid of Heliothrips haemorrhoidalis (Bouché) (Thysan., Thripidae)

Abstract:  The endoparasitoid Thripobius semiluteus Bouček was recently introduced to Italy from Israel for the biological control of Heliothrips haemorrhoidalis (Bouché). In this study, some aspects of the biology of T. semiluteus were determined in the laboratory. Developmental time (egg to adult), potential fecundity, realized fecundity, progeny, daily rate of deposition of eggs and several demographic growth parameters were evaluated. Studies of the longevity of fed and starved adults at seven temperatures (3, 10, 15, 20, 23, 25 and 30 ± 1°C) showed that fed T. semiluteus lived longest at 15°C (36.45 days) and shortest at 3°C (1.45 days). Longevity was reduced significantly at higher and lower temperatures than 15°C and when honey was not provided. Development time was measured at six temperatures. Pupae did not complete development at 10°C. The lower theoretical temperature threshold was 9.0°C; the optimum developmental temperature and the upper lethal threshold were 28.0°C and 34.1°C respectively. The most rapid development was found at 30°C, but waSPS suffered significantly higher mortality at this temperature than at other temperatures. Ovigeny index showed that T. semiluteus is synovigenic, with a mean realized fecundity of 78.8 eggs per female. The mean progeny was 68.2 adults per female on fed adults.     

Effect of temperature on the survival and infectivity of <Emphasis Type="Italic">Pseudotheraptus devastans</Emphasis> vector

The aim of this study was to investigate under a controlled environment, the effect of temperature on the survival and infectivity of Pseudotheraptus devastans Distant, a cassava anthracnose disease vector. The insect P. devastans was collected from young cassava (Manihot esculenta Crantz) field plots, at the International Institute of Tropical Agriculture, (IITA), Ibadan, Nigeria. A mixture of the different developmental stages of eggs, first to fifth instar nymphs, and adults, were incubated in controlled environment chambers, under various constant temperatures of: 15, 17, 22, 25, 27, 30, and 35°C. Relative humidity at different temperature conditions were recorded and maintained at 90%, 85%, 80%, 75%, 70%, 65%, and 60%, respectively. A significant increase in insect survival was observed between 22 and 27°C temperature conditions while a significant decrease in survival was observed at 15°C and above 30°C. Lesion number, lesion diameter and infectivity among the insect stages varied as a function of temperature and relative humidity. Infectivity was highest at 22–25°C maintained at 75–80% RH and lowest at 15°C and above 30°C maintained respectively, at 65% RH and 90% RH. There was considerable low vector infectivity due to low survival of the insects at extreme temperatures.