The role of oxygen availability in the embryonation of Heterakis gallinarum eggs

The importance of oxygen availability in the embryonation of the infective egg stages of the gastrointestinal nematode parasite Heterakis gallinarum was studied in the laboratory. Unembryonated H. gallinarum eggs were kept under either aerobic conditions by gassing with oxygen, or anaerobic conditions by gassing with the inert gas nitrogen, under a range of constant temperatures. Oxygenated eggs embryonated at a rate influenced by temperature. Conversely, eggs treated with nitrogen showed no embryonation although when these eggs were transferred from nitrogen to oxygen gas after 60 days of treatment, embryonation occurred. This demonstrated that oxygen is an essential requirement for H. gallinarum egg development, although undeveloped eggs remain viable, even after 60 days in low oxygen conditions. The effects of climate on the biology of free-living stages studied under constant laboratory conditions cannot be applied directly to the field where climatic factors exhibit daily cycles. The effect of fluctuating temperature on development was investigated by including an additional temperature group in which H. gallinarum eggs were kept under daily temperature cycles between 12 and 22°C. Cycles caused eggs to develop significantly earlier than those in the constant mean cycle temperature, 17°C, but significantly slower than those in constant 22°C suggesting that daily temperature cycles had an accelerating effect on H. gallinarum egg embryonation but did not accelerate to the higher temperature. These results suggest that daily fluctuations in temperature influence development of the free-living stages and so development cannot be accurately predicted on the basis of constant temperature culture.     

Stochasticity accelerates nematode egg development

Day-degrees models of nematode development assume that temperature stochasticity has no effect on the development rate of infective stages as long as the mean temperature is held constant. This assumption was tested in this study. Unembryonated Heterakis gallinarum eggs were subjected to nocturnal and diurnal daily temperature cycles at 12 and 17 C. respectively, and embryonation was compared with eggs subjected to similar stochastic daily cycles, in which random normal variations in the temperature were added to the 2 temperatures. The prediction that there is no effect of stochasticity was refuted. Embryonation of eggs subjected to variable daily cycles occurred significantly earlier than that of eggs subjected to deterministic daily cycles, suggesting that stochastic variation in temperature accelerated embryonation even though mean temperatures were the same. These findings show that the development time of H. gallnarum eggs is decreased by stochastic variation in temperature, which may have important implications for the effects of climate change on parasite availability.     

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.     

The effects of constant and changing tempertures on the development of eggs of the freshwater snail Lymnaea auricularia (L.)

The rate of development of Lymnaea auricularia eggs was studied at various constant temperatures between 10° and 36°C. Development was accelerated as the temperature increased and at 36°C the eggs failed to develop. Spring eggs showed differences in their rate of development when compared with summer eggs when measured at similar tempertures.

Both spring and summer eggs were more than 90% fertile. Hatching success was high at temperatures between 10° and 30° (100%–82/9%); while at 34°C it was reduced to 60.6% for spring eggs. It was above 87% at temperatures between 10° and 34°C but it dropped to 62.3% at 36°C for summer eggs.

In one regularly changing temperature experiment a significant acceleration (P < .05) was found. In two others there was no significant difference beween predicted and observed egg durations. In one suddenly changing temperature regime (1 day at 20°, 1 day at 30° and so on) a huge retardation of development was found. In the other suddenly changing experiment (1 day at 15°, 1 day at 25°) no significant difference was found.

The exposure of eggs to extreme temperature (4°C, freezing and 4°C caused a retardation in the race of subsequent development of eggs at 25°C.     

The effect of temperature on the duration of the egg stage of certain sciomyzid flies which predate Lymnae truncatula

1. 1. The effect of temperature on the duration of the egg stage of 3 species of sciomyzid flies was investigated at 14, 17, 20, 23 and 26°C.

2. 2. Ilione albiseta(Scopoli): the mean duration of the egg stage (m.d.e.s) decreased from 88.53 to 34.05 days as temperature increased up to 26°C. Under changing temperature conditions (14↔20°C) there was a significant retardation in the duration of the egg stage. 50–70% of conditioned embryonated eggs (i.e. eggs maintained on moist filter paper from 10 to 20 days at 23°C) hatched within 24 in a 0.1% solution of ascorbic acid. (Embryonation was judged to have taken place when the cephalopharyngeal skeleton was visible through the chorion and there was evidence of larval movement within the egg.)

3. 3. Limnia unguicornis (Scopoli): the m.d.e.s. at the 5 constant temperatures was very variable but was significantly shorter at 26°C (22.85 days) than at 14 and 17°C (29.8 and 32.48 days respectively).

4. 4. Pherbellia cinerella (Fallén): the m.d.e.s. decreased from 14.73 days at 14°C to 4.42 days to 26°C and percentage hatch was greatest at 14°C.

Effect of Temperature on Embryonation of Ascaris suum Eggs in an Environmental Chamber

The influence of temperature on the development and embryonation of Ascaris suum eggs was studied using coarse sand medium in an environmental chamber with 50% humidity. The time required for development and embryonation of eggs was examined under 3 different temperature conditions, 5℃, 25℃, and 35℃. A. suum eggs did not develop over 1 month at the temperature of 5℃. However, other temperature conditions, 25℃ and 35℃, induced egg development to the 8-cell-stage at days 5-6 after incubation. All eggs examined developed to the 8-cell stage at day 6 after incubation in the sand medium at 25℃. The higher temperature, 35℃, slightly accelerated the A. suum egg development compared to 25℃, and the development to the 8-cell stage occurred within day 5 after incubation. The formation of larvae in A. suum eggs at temperatures of 35℃ and 25℃ appeared at days 17 and 19 after incubation, respectively. These findings show that 35℃ condition shortens the time for the development of A. suum eggs to the 8-cell-stage in comparison to 25℃, and suggest the possibility of accelerated transmission of this parasite, resulting from global warming and ecosystem changes.     

Prey-Dependent Life Attributes of an Aphidophagous Ladybird Beetle, Propylea dissecta (Coleoptera: Coccinellidae)

Predation potential, development, immature survival and reproduction of an aphidophagous ladybeetle, Propylea dissecta (Mulsant) was studied when fed on seven aphid prey, viz. Aphis gossypii, Aphis craccivora, Lipaphis erysimi, Uroleucon compositae, Brevicoryne brassicae, Rhopalosiphum maidis and Myzus persicae. A. gossypii was most suitable and consumed by the larvae and adults of P. dissecta, while M. persicae, the least. Pre-imaginal development of P. dissecta was fastest (0.080 day^-1) when A. gossypii was used as prey, whilst slowest (0.061 day^-1) on M. persicae. The immature survival, adult emergence, adult male and female longevity of P. dissecta was maximal (i.e., 77.10±0.04 and 93.21±0.79%, 57.10±1.62 and 62.40±1.93 days, respectively) on A. gossypii and minimal (i.e., 63.01±1.87 and 81.73±1.79%, 42.50±1.21 and 49.40±2.32 days, respectively) when M. persicae was provided as prey. Oviposition period, fecundity, percent egg viability and mean reproductive rate was maximum (i.e., 50.30±2.03 days, 856.00±30.00 eggs, 96.40±0.31% and 17.02 eggs per day) on A. gossypii, and minimum (i.e., 18.00±1.40 days, 212.00±18.21 eggs, 72.46±2.81% and 11.78 eggs per day) on M. persicae. Adult weight and developmental rate of P. dissecta have a positive correlation, which suggests that if immature stages of ladybeetle developed faster, they should grow into heavier adults. Female longevity and fecundity also have a positive correlation. The findings also reveal that all seven aphid species tested are essential food. Rank order of prey species was consistent in all experimental parameters.     

Lumen phase specific cross immunity between Hymenolepis microstoma and H. nana in mice

, and 1988. Lumen phase specific cross immunity between Hymenolepis microstoma and H. nana in mice. International Journal for Parasitology 18: 1019–1027. When mice inoculated with five cysticercoids of Hymenolepis microstoma were challenged with H. nana, they showed strong resistance to challenges with both eggs and cysticercoids of H. nana from day 20. The immunity became complete from day 30 onward: no tissue cysticercoids or lumenal adults of H. nana were established in these mice. However, when mice were challenged with H. nana 10 or 20 days after 10-day old immature H. microstoma were removed by an anthelmintic, the immunity evoked was directed exclusively against the lumenal phase of the cysticercoid challenge but not the tissue cysticercoids of the egg challenge. When mice experienced the prepatent infection with H. microstoma twice, the immunity evoked was also against the lumenal phase of the egg challenge: the oncospheres developed into tissue cysticercoids but thereafter completely failed to develop into lumenal adult tapeworms. Infection with a single cysticercoid of H. microstoma was shown to be sufficient to evoke immunity against H. nana cysticercoid infections in two strains of mice. Sera from mice which experienced a patent infection with H. microstoma revealed that IgG, IgA, IgM isotypes reacted against oncospheres and cysticercoids of both species, while sera from mice which experienced two prepatent infections reacted with cysticercoids only. Sera from H. microstoma infected mice resistant to H. nana caused precipitations on 4-day-old H. nana in vitro. A correlation exists between the presence of stage specific antibodies and resistance to the different stages.     

Relationships among salinity, egg size, embryonic development, and larval biomass in the estuarine crab Chasmagnathus granulata Dana, 1851

We studied interrelationships between initial egg size and biomass, duration of embryogenesis at different salinities, and initial larval biomass in an estuarine crab, Chasmagnathus granulata. Ovigerous females were maintained at three different salinities (15‰, 20‰ and 32‰); initial egg size (mean diameter), biomass (dry weight, carbon and nitrogen) as well as changes in egg size, embryonic development duration, and initial larval biomass were measured.

Initial egg size varied significantly among broods from different females maintained under identical environmental conditions. Eggs from females maintained at 15‰ had on average higher biomass and larger diameter. We hypothesise that this is a plastic response to salinity, which may have an adaptive value, i.e. it may increase the survivorship during postembryonic development. The degree of change in egg diameter during the embryonic development depended on salinity: eggs in a late developmental stage were at 15‰ significantly larger and had smaller increment than those incubated at higher salinities. Development duration was longer at 15‰, but this was significant only for the intermediate embryonic stages. Initial larval biomass depended on initial egg size and on biomass loss during embryogenesis. Larvae with high initial biomass originated either from those eggs that had, already from egg laying, a high initial biomass (reflecting individual variability under identical conditions), or from those developing at a high salinity (32‰), where embryonic biomass losses were generally minimum. Our results show that both individual variability in the provisioning of eggs with yolk and the salinity prevailing during the embryonic development are important factors causing variability in the initial larval biomass of C. granulata, and thus, in early larval survival and growth.     

The effect of constant and changing temperatures on the development rates of the eggs and larvae of Ostertagia ostertagi

The duration of the egg stage at constant temperature showed a decrease with increasing constant temperature up to 30°; above this, there was a slight increase in the duration and a decrease in survival. Regularly changing temperature had a slight but significant retarding effect on egg duration in one experiment but in the second, there was no significant effect. In two experiments in which there were two sudden changes of temperature in the same direction, there was no significant effect. The duration of the larval stages from hatching up to the third stage showed a decline with increasing constant temperature up to 25°. Survival was poor at 30°. The larvae were fed on E. coli cultures. In the regularly changing experiments on the larvae one showed a slight retardation and the second an acceleration in development. Both were significant (P < .05). In the experiments in which temperature changed in two sudden jumps in the same direction, one showed a slight acceleration and the other showed no effect. It is concluded that the effects of changing temperature while significant are probably not large enought to be of significance in nature. Newly hatched and third stage larvae grown at constant temperatures showed a tendency to be longer at higher temperatures.     

Fecundity studies of neritic calanoid copepods Acartia clausi Giesbrecht and A. Steueri Smirnov: A simple empirical model of daily egg production

Fecundity studies of neritic calanoid copepods, Acartia clausi Giesbrecht and A. steueri Smirnov, were made under controlled laboratory conditions. Effects of temperature and food abundance upon daily egg production were intensively investigated. Under food-satiated conditions, the daily reproductive rate was a function of temperature, and, at constant temperature, it was a function of chlorophyll a concentration. A simple model equation describing fecundity was derived from the combined effects of temperature and chlorophyll a on daily egg production. The observed daily reproductive rates of natural populations of Acartia were simulated closely by the simple model.     

Partial ecological life table of immature Helicoverpa zea (Lepidoptera: Noctuidae) in an irrigated cotton cropping system in the Trans-Pecos region of Texas, USA

During the summers of 1996 and 1997 cotton bollworm, Helicoverpa zea (Boddie), life stages were sampled in insecticide-free, irrigated cotton, Gossypium hirsutum L., in the Trans-Pecos region of Texas. Partial ecological life tables were constructed for one generation of H. zea in each of the two growing seasons. Partial generation mortality (egg to fifth-instar) surpassed 97% in both years. The egg stage exhibited the greatest amount of real (r_x) and apparent (q_x) mortality followed by the third-instar. One hundred percent of the collected life stages consisted of H. zea. Egg parasitism ranged from 4.1 to 6% and egg predation by Orius tristicolor (White) was 4.1% in 1996 and 13.2% in 1997. Unexplained factors made the greatest contribution to H. zea mortality regardless of the life stage sampled. Each cotton bollworm generation monitored in 1996 and 1997 exhibited a Type III survivorship curve. As a result of the extensive early life stage mortality, rescue management tactics associated with contemporary H. zea control in the region appears to be generally unnecessary for cotton grown under irrigation in the Trans-Pecos region.     

The Influence of Host Species on Some Biological and Behavioural Aspects of Dibrachys boarmiae (Hymenoptera: Pteromalidae), Parasitoid of Kermania pistaciella (Lepidoptera: Tineidae)

Dibrachys boarmiae was recently found as a parasitoid of the pistachio twig borer moth, Kermania pistaciella, an important pistachio pest in Iran. Several biological and behavioural aspects of the wasp were studied under controlled conditions using three different lepidopterous host species, K. pistaciella, Sitotroga cerealella and Galleria mellonella. Development time from egg to adult decreases from 54 days at 15°C to 12.6 days at 32.5°C. The thermal constant was estimated 270°D, and the lower development threshold was at 9.9°C. Longevity of females that had the opportunity to oviposit and access to food (honey) was on average 23 days, and 134 offspring were produced during 13 days of oviposition. Ninety percent of ovipositions occur during the first 10 days of the parasitoid's life, although no pre-oviposition period was found. If females were deprived of food, longevity as well as fecundity, were drastically reduced to 8 days and only 79 offspring respectively. Females were able to mate immediately after emergence and the sex ratio of the progeny was strongly female biased on all examined hosts, especially on the largest host G. mellonella (0.08 male). When females were kept with a male throughout their life, the total number of progeny decreased to 92 wasps on average but the sex ratio was unaffected. The parasitoid significantly preferred to attack the pre-pupal stage, and this influenced the size of clutches allocated to different host stages. The parasitoid laid larger clutches on bigger hosts.     

The effect of oxygen and carbon dioxide on the development of the free-living stages of Strongyloides ratti in axenic culture

The effect of oxygen and carbon dioxide concentration on the development of the free-living stages of Strongyloides ratti in axenic culture was examined. Hatching of S. ratti eggs was inhibited at very low oxygen levels. Development of all organisms was inhibited in medium gassed with less than 4% O2 in 0.03% CO2 with the remainder N2. Between 8 and 21% O2 there was no significant difference in the percentage developing directly to filariform larvae, free-living females, or free-living males. Cultures gassed with CO2 concentrations greater than 1% in 21% O2 with the remainder N2 manifested inhibited development to filariform larvae, whereas concentrations between 5 and 7.5% enhanced development to free-living females. There was a positive effect on increasing the CO2 concentration from 0.03% to 5% on development to filariform larvae and male worms at levels of 1% and 2% oxygen in nitrogen, respectively. Direction of development, either directly to the filariform larva or to the free-living female, was influenced by CO2 and O2 concentrations encountered by the egg or the newly hatched larva of the parasitic female in axenic culture. The axenic culture system permits an important experimental approach to the study of factors modulating the differentiation of the free-living stages of Strongyloides.     

Population dynamics of Haemonchus contortus and Trichostrongylus spp. in sheep

Twenty-five lambs grazing a parasite-contaminated pasture were divided into four groups. One group of seven lambs were left untreated and three groups of six lambs each were treated with levamisole at 2 week, 3 week or 1 month intervals respectively. Body weights, fecal egg counts and packed cell volumes were determined every 2 weeks for 8 weeks. Lambs were then necropsied on the day they would have received another treatment, thus the maximum accumulation of parasites at each treatment frequency was measured. Treatment at 2 and 3 week intervals markedly suppressed fecal egg counts, but egg counts of sheep treated every month rose between treatments and untreated animals continually shed eggs. Treatment at all three frequencies provided only slight protection from blood loss, but it lessened weight loss. There was little difference between treatment groups in burdens of adult H. contortus, but burdens of T. axei and T. colubriformis and arrested larvae of H. contortus increased with decreasing frequency of treatment. The results support the findings of other workers that Trichostrongylus spp. have a long adult life span and continue to accumulate with time, whereas H. contortus may have a short adult life span and a rapid population turnover. In the face of constant reinfection, repeated anthelmintic treatment gives more protection from the effects of the long-lived parasites than from those with a rapid population turnover.     

Temperature dependent eclosion rhythmicity in the high altitude Himalayan strains of Drosophila ananassae

The circadian pacemaker controlling the eclosion rhythm of the high altitude Himalayan strains of Drosophila ananassae captured at Badrinath (5123 m) required ambient temperature at 21°C for the entrainment and free-running processes. At this temperature, their eclosion rhythms entrained to 12h light, 12h dark (LD 12:12) cycles and free-ran when transferred from constant light (LL) to constant darkness (DD) or upon transfer to constant temperature at 21°C following entrainment to temperature cycles in DD. These strains, however, were arrhythmic at 13 or 17°C under identical experimental conditions. Eclosion medians always occurred in the thermophase of temperature cycles whether they were imposed in LL or DD; or whether the thermophase coincided with the photophase or scotophase of the concurrent LD 12:12 cycles. The temperature dependent rhythmicity in the Himalayan strains of D. ananassae is a rare phenotypic plasticity that might have been acquired through natural selection by accentuating the coupling sensing mechanism of the pacemaker to temperature, while simultaneously suppressing the effects of light on the pacemaker.     

Development rate of copepod eggs of the genus Calanus

The development time to hatching of eggs of four closely related species of copepods, Calanus helgolandicus (Claus), C. finmarchicus (Gunn.), C. glacialis Jaschnov, and C. hyperboreus Kröyer as a function of temperature is given by .

The constant a is positively correlated with egg diameter, so that large eggs take longer to develop than small eggs. The value of the constant is related to the geographical range of the species.     

A stochastic development fraction model for predicting the development of the nematode parasite of sheep, Haemonchus contortus from egg to infective larvae under the influence of temperature

1. 1 Regression models for predicting the minimum, the median and the maximum period of development of the parasite H. contortus from egg to the infective stage of constant temperature were described.

2. 2. Simulations were used to study the development of the parasite to the infective stage.

3. 3. Further, an analytic Stochastic Development Fraction Model was used to reproduce the development of the parasite obtained by simulations.

4. 4. The Stochastic Development Fraction Model was compared with the Deterministic Development Fraction Model to expose its potentials for predicting the development of parasites on pasture where varying temperature prevail.

Effect of temperature on developmental time and longevity of Psyttalia cosyrae (Hymenoptera: Braconidae)

Psyttalia cosyrae (Wilkinson) (Hymenoptera: Braconidae) is a koinobiont, solitary larval-pupal parasitoid of Ceratitis cosyra (Walker) (Diptera: Tephritidae), and possibly other tephritid fruit flies. The effect of temperature on developmental time and longevity of this parasitoid was investigated and the thermal requirement at six constant temperatures (15±0.5, 20±0.5, 25±0.5, 27±0.5, 30±0.5, and 33±0.05°C) and 60-70% R.H was determined. The developmental rate increased with an increase in temperature. Females took a longer time to complete development than males at all temperatures tested. Development from egg to adult emergence required 244 degree-days (DD) above a thermal threshold of 11.9°C for both sexes pooled, 233 DD above 12.0°C for males and 256 DD above 11.6°C for females. Adult longevity was affected by temperature, and females lived longer than males at all temperatures tested.     

Presence of circadian rhythms in the locomotor activity of a cave-dwelling millipede Glyphiulus cavernicolus sulu (Cambalidae, Spirostreptida)

The locomotor activity of the millipede Glyphiulus cavernicolus (Spirostreptida), which occupies the deeper recesses of a cave, was monitored in light-dark (LD) cycles (12h light and 12h darkness), constant darkness (DD), and constant light (LL) conditions. These millipedes live inside the cave and are apparently never exposed to any periodic factors of the environment such as light-dark, temperature, and humidity cycles. The activity of a considerable fraction of these millipedes was found to show circadian rhythm, which entrained to a 12:12 LD cycle with maximum activity during the dark phase of the LD cycle. Under constant darkness (DD), 56.5% of the millipedes (n = 23) showed circadian rhythms, with average free-running period of 25.7h ± 3.3h (mean ± SD, range 22.3h to 35.0h). The remaining 43.5% of the millipedes, however, did not show any clear-cut rhythm. Under DD conditions following an exposure to LD cycles, 66.7% (n = 9) showed faint circadian rhythm, with average free-running period of 24.0h ± 0.8h (mean ± SD, range 22.9h to 25.2h). Under constant light (LL) conditions, only 2 millipedes of 11 showed free-running rhythms, with average period length of 33.3h ± 1.3h. The results suggest that these cave-dwelling millipedes still possess the capacity to measure time and respond to light and dark situations. (Chronobiology International, 17(6), 757-765, 2000)