Characterisation of proteases involved in egg hatching of the sheep blowfly, Lucilia cuprina

A number of proteases were identified in the egg shell washings (ESW) collected during the egg hatching of Lucilia cuprina (sheep blowfly). Characterization of these proteases indicated a pH optima in a similar pH range that was optimal for L. cuprina egg hatching. Mechanistic characterization of these proteases indicated that they were predominantly of the serine class. Several protease inhibitors were tested for their ability to inhibit L. cuprina egg hatching in vitro. Egg hatching was significantly (P<0.05) inhibited by PMSF (61%), 1,10-Phenanthroline (42%) and Pepstatin (29%). The inhibition of egg hatching by PMSF showed a strong concentration dependence, with its effects ranging from inhibition at high concentrations to enhancement of egg hatching at low concentrations. Addition of ESW to unhatched eggs, significantly (P<0.05) enhanced their rate of hatching above untreated control eggs. This enhancement of egg hatching was significantly (P<0.05) reversed by the protease inhibitors Elastatinal (40%), 1,10-Phenanthroline (40%) and PMSF (38%). These studies indicate a role for serine and/or metallo-proteases in facilitating L. cuprina egg hatch.     

Induced hatching to avoid infectious egg disease in whitefish.

Reacting to a threat before physical contact, e.g., induced by air- or water-borne substances, appears to be an elegant way of defense. The reaction may be behavioral, developmental, morphological, or physiological, and it can involve a shift in niche or life history. Hatching from eggs is a shift in niche and in life history. From niche shift and life history models, one would predict that the timing of hatching is, to some degree, phenotypically plastic, i.e., early or delayed hatching is likely to be inducible. Temporary increased larval mortality (e.g., increased predation on larvae) would favor delayed hatching, while relatively high egg mortality would favor early hatching. Here, I show experimentally that eggs of the whitefish (Coregonus sp.) hatch earlier in the presence of a virulent egg parasite and that this early hatching is induced by water-borne cues emitted from infected eggs.     

Improvement of egg hatch of Ceratitis capitata (Diptera: Tephritidae) for enhanced output

Embryonated eggs of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) genetic sexing strain (GSS), VIENNA 8 were treated with low concentrations of five disinfectants-formaldehyde, iodine, sodium hypochlorite, peracetic acid, and quaternary ammonium--for decontamination and egg hatch improvement. The newly laid eggs were successfully treated with formaldehyde at 100 ppm for 1 min with 74.2% hatching and with quaternary ammonium at 150 ppm for 1 and 2 min with 70.4 and 69% hatching, respectively. Increased formaldehyde concentration may have affected the embryos, because it resulted in a decrease in the hatching percentage. However, egg viability was not impaired and hatch was not affected by quaternary ammonium treatment compared with controls and eggs treated with other disinfectants. Quaternary ammonium shows promise for decontaminating eggs and improving egg hatch.     

Influence of Inoculum Density,Host, and Low-temperature Period on Delayed Hatch of Meloidogyne javanica Eggs

Most eggs of M. javanica hatch within several days when incubated in water. Those that do not are said to show delayed hatching. Several experiments were conducted to determine the effect of specific conditions on the percentage of eggs with delayed hatch. Six initial inoculum densities ranging from 100 to 20,000 eggs per pot did not influence egg hatch within a 45-day incubation period. In a 60-day test, the percentage of eggs hatching after more than 20 days was low for egg masses removed from carrot and okra and high for those from pepper and bean. Increasing exposure to cold temperature (8 C) from 7 to 30 days tended to delay hatch.     

Variation in the hatching behaviour of Nematodirus battus: Polymorphic bet hedging?

Previous work on the transmission dynamics of Nematodirus battus, an important nematode parasite of farmed ruminants in temperate regions, suggests that it operates a bet-hedging strategy. Hatching of cold-sensitised eggs is concentrated in spring, while alternative hatching of non-cold-sensitised eggs in autumn mitigates the risk of poor conditions for hatching in spring or host absence during peak larval availability. Isolates from Scotland showed much less propensity to hatch without chilling than the previously characterised isolate from southern England. Nematodirus battus eggs from a hill farm in Scotland showed intermediate proportions of non-chilled hatching, perhaps related to unpredictability of climate at higher altitudes. Geographic polymorphism in larval behaviour appears to be present in the form of differing chilling requirements for egg hatching. Since bet-hedging through trait diversification is a plausible and demonstrated strategy for coping with environmental unpredictability, it is a likely target for adaptation to climate change. Predictions of disease epidemiology in a changing climate should incorporate parasite adaptation, but further theoretical and empirical characterisations of likely evolutionary responses are needed before this is possible for the most economically important systems.     

The hatching time of Locusta migratoria under outdoor conditions: role of temperature and adaptive significance

The present study investigates the time of hatching of the migratory locust Locusta migratoria using egg pods that are artificially buried in the soil under outdoor conditions. Most eggs hatch in the mid‐morning, with a peak between 11.00 and 12.00 h, and none hatch before 09.00 or after 16.00 h. Furthermore, most egg pods complete hatching within a day, although some take 2 or 3 days, and egg hatching is interrupted by rain. There are no large differences in hatching time from May to September. Laboratory experiments in which the eggs are exposed to temperatures simulating outdoor conditions show that soil temperature is the main factor controlling hatching activity. The increase in temperature in the morning appears to trigger egg hatching, as confirmed by laboratory experiments, which may explain the similar hatching times between seasons. The seasonal patterns of temperature variation and hatching time suggest that the hatching time of L. migratoria eggs may be adjusted to allow the hatchlings to be exposed to high temperatures in the afternoon so that they can harden their bodies quickly.     

Bacteria stimulate hatching of yellow fever mosquito eggs

Background

Aedes aegypti Linnaeus is a peridomestic mosquito that lays desiccation-resistant eggs in water-filled human-made containers. Previous investigations connected egg hatching with declining dissolved oxygen (DO) that is associated with bacterial growth. However, past studies failed to uncouple DO from other potential stimulatory factors and they contained little quantitative information about the microbial community; consequently, a direct role for bacteria or compounds associated with bacteria in stimulating egg hatching cannot be dismissed.

Methodology/Principal Findings

Environmental factors stimulating hatch of Ae. aegypti eggs were investigated using non-sterile and sterile white oak leaf (WOL) infusions and a bacterial culture composed of a mix of 14 species originally isolated from bamboo leaf infusion. In WOL infusion with active microbes, 92.4% of eggs hatched in 2-h at an average DO concentration of 2.4 ppm. A 24-h old bacterial culture with a DO concentration of 0.73 ppm also stimulated 95.2% of eggs hatch within 1-h. In contrast, only 4.0% of eggs hatched in sterile infusion, whose DO averaged 7.4 ppm. Effects of bacteria were uncoupled from DO by exposing eggs to bacterial cells suspended in NaCl solution. Over a 4-h exposure period, 93.8% of eggs hatched while DO concentration changed minimally from 7.62 to 7.50 ppm. Removal of bacteria by ultra-filtration and cell-free filtrate resulted in only 52.0% of eggs hatching after 4-h at an average DO concentration of 5.5 ppm.

Conclusions/Significance

Collectively, the results provide compelling evidence that bacteria or water-soluble compounds secreted by bacteria, not just low DO concentration, stimulate hatching of Ae. aegypti eggs. However, the specific cues involved remain to be identified. These research findings contribute new insight into an important aspect of the oviposition biology of Ae. aegypti, a virus vector of global importance, providing the basis for a new paradigm of environmental factors involved in egg hatching.     

大豆胞囊线虫的休眠

以前研究发现,辽宁地区大豆生长期间及收获期土壤中胞囊孵出的二龄幼虫量很少,推测线虫卵的休眠与大豆生长时期或季节相关。为明确该地区大豆胞囊线虫的休眠特点,2002-2003年采用田间随机多点取样、室内分离及模拟自然条件孵化等方法对大豆胞囊线虫的休眠进行深入研究。结果表明:在生长季节,感病品种辽豆10根围土壤中的白色雌虫、卵囊及褐色的胞囊均可孵出二龄幼虫,且孵化持续时间较长,第21d仍有幼虫孵出,白色雌虫及卵囊内的卵孵化率高于褐色胞囊;不同作物对其根围土壤中胞囊内卵的孵化影响不大,寄主作物大豆、非寄主作物玉米根围及休闲地土壤中的胞囊在条件适宜均可孵出二龄幼虫;季节对胞囊内卵的孵化有较大的影响,出苗期孵化率最高,收获期最低,2周时平均1个胞囊孵出幼虫分别为83.8和9.7条;胞囊皮对线虫卵的孵化有显著的影响。表明沈阳地区大豆胞囊线虫在正常和逆境条件下均有部分卵表现休眠。     

Laboratory studies of factors affecting egg hatch of triops longicaudatus (LeConte) (Notostraca : Triopsidae)

Egg hatch was greatest (78.33%) for eggs not previously desiccated. A reduction in numbers hatched occurred as the relative humidity at which they were dried decreased. Some eggs hatched (0.67–79.33%) at pH levels of 3.10–10.01 with the highest hatch at pH 5.60. Water temperature greatly affected egg hatch. No hatch occurred until temperatures were above 14°C. A constant 29°C significantly inhibited hatching. Egg hatch increased 13.00 to 43.42% as salinity decreased from 2200 to 9.24 micromhos/cm. As little as 13 mm of flooded soil covering the eggs prevented them from hatching for 14 days. Eighteen percent hatch resulted when soil and eggs were redistributed to a 1 mm soil layer. Egg samples from the same parent, even though treated similarly, often hatched at greatly varying rates and only rarely was hatching 100% within a replication.     

Evidence for embryo–embryo interactions in controlling hatching time and synchronization in the brown marmorated stink bug,Halyomorpha halys (Hemiptera: Pentatomidae)

The mechanisms controlling egg diapause and circadian rhythms of hatching activity have been extensively studied in insects. However, relatively little attention has been paid to the mechanisms controlling synchronized hatching from an egg mass. In this study, we examined the possible involvement of embryo–embryo interaction in controlling hatching time in Halyomorpha halys (Stål). Eggs tended to hatch earlier as the egg mass size increased. Egg separation and clumping of separated eggs at various times showed that hatching synchrony was largely determined shortly before hatching. However, whether eggs were kept in a mass or separated until several hours before hatching also influenced the hatching time, indicating the presence of embryo–embryo interactions. Eggs derived from different masses and kept in physical contact with one another hatched synchronously if their ages were within approximately 8 h. In this case, both younger and older eggs advanced only in hatching time, in contrast to a case of locusts reported by others. Eggs separated by more than 7 mm hatched as synchronously as those kept in a mass when glued to the same substrate, suggesting an important role of the egg substrate in transmitting the vibrational hatching signals to neighboring sibling eggs to synchronize hatching.     

Egg hatching of mosquitoes Aedes caspius and Ae. vittatus stimulated by water vibrations

Simple laboratory experiments with eggs of wild-caught Aedes caspius (Pallas) and Aedes vittatus (Bigot) mosquitoes (Diptera: Culicidae) demonstrated that egg hatch rates (i.e. percentage hatching daily) increased significantly in response to water vibrations caused by finger-tip drumming on containers of submerged eggs. When disturbed by daily vibrations for only 30 s, eggs hatched sooner than when they remained flooded or were periodically drained and reflooded without agitation. For autogenous Ae. caspius from saltmarsh, egg hatch rates were three- to four-fold greater for groups of 50 eggs than for solitary eggs, possibly due to chemicals (functional kairomones) emanating from other eggs or larvae. For anautogenous Ae. vittatus from freshwater rock-pools, tapping the container daily (for 30 s each 2 h in 8 h) hatched 93% of eggs, compared with only 42% hatch of eggs agitated only when first flooded or 55% hatch of eggs dried and reflooded three times during 17 days without other disturbance. It is concluded that, apart from flooding and other factors, vibrations - simulating the patter of rainfall provide a very significant hatching stimulus for Aedes eggs.     

The chemical nature of host hatching factors in the monogenean skin parasites Entobdella soleae and Acanthocotyle lobianchi

Fully-developed eggs of the monogenean Entobdella soleae from the skin of the common sole (Solea solea) hatch when treated with dilute solutions of urea or ammonium chloride in sea water. There is some evidence that arginine may stimulate hatching but the eggs do not respond when treated with sea water solutions containing trimethylamine oxide or glutamine. Sole skin mucus contains sufficient urea to stimulate hatching but insufficient ammonia. Solutions of urea in sea water stimulate hatching in the monogenean parasite Acanthocotyle lobianchi found on ray skin. Sea water solutions containing ammonium chloride and trimethylamine oxide failed to hatch the eggs of A. lobianchi and the eggs were also insensitive to various amino acids made up at concentrations found in host mucus. Experiments with urease confirmed that urea in ray ventral skin mucus is the host hatching factor for A. lobianchi. Skin mucus from the common sole failed to stimulate hatching in A. lobianchi. The role as hatching factors of excretory products in host gill effluent, skin mucus and urine is discussed.     

Corticosterone stimulates hatching of late-term tree lizard embryos

The regulation of hatching in oviparous animals is important for successful reproduction and survival, but is poorly understood. We unexpectedly found that RU-486, a progesterone and glucocorticoid antagonist, interferes with hatching of viable tree lizard (Urosaurus ornatus) embryos in a dose-dependent manner and hypothesized that embryonic glucocorticoids regulate hatching. To test this hypothesis, we treated eggs with corticosterone (CORT) or vehicle on Day 30 (85%) of incubation, left other eggs untreated, and observed relative hatch order and hatch time. In one study, the CORT egg hatched first in 9 of 11 clutches. In a second study, the CORT egg hatched first in 9 of 12 clutches, before vehicle-treated eggs in 10 of 12 clutches, and before untreated eggs in 7 of 9 clutches. On average, CORT eggs hatched 18.2 h before vehicle-treated eggs and 11.6 h before untreated eggs. Thus, CORT accelerates hatching of near-term embryos and RU-486 appears to block this effect. CORT may mobilize energy substrates that fuel hatching and/or accelerate lung development, and may provide a mechanism by which stressed embryos escape environmental stressors.     

CLUTCH SIZE, EGG SIZE, HATCH WEIGHT AND LAYING DATE IN RELATION TO EARLY MORTALITY IN RED GROUSE LAGOPUS LAGOPUS SCOTICUS CHICKS

Clutches of Red Grouse eggs were collected from the wild and subsequent hatching and rearing done in standard conditions in captivity. Variations in chick survival from one clutch to another in the same year were related to differences in hatch weight. Hatch weight was determined only partly by egg size. Weight loss between laying and hatching was related to survival independently of egg size. Variation in this weight loss obscured any simple relationship between egg size and survival, except in eggs laid by captive hens. Intrinsic differences amongst hens caused some variations in laying date, egg size, hatch weight and chick survival. Variations in egg size and hatch weight accounted for less than half the variation in survival; other unmeasured intrinsic factors were also important. Big clutches hatched earlier than small ones. The commonest clutches were of seven and eight eggs, with six and nine frequent. Very big clutches of ten or more eggs were infrequent and chicks from them sometimes survived worse than from smaller clutches. As in other species, the commonest clutch sizes were not the most productive. There was no simple relationship between egg size and clutch size.     

Patterns in the abundance,phenology, and hatching of the resting egg stage of the invasive zooplankter <Emphasis Type="Italic">Bythotrephes longimanus</Emphasis>: implications for establishment

To examine how dormancy contributes to the establishment and persistence of Bythotrephes longimanus, we investigated resting egg production and hatching in relation to the demography of the planktonic stage and environmental conditions in Island Lake Reservoir (USA). During a 3-year study, the largest contribution to the egg bank occurred in autumn and most eggs hatched in spring, but we also detected some resting egg production and hatching in summer. The difference between summer and late autumn densities of eggs in sediments averaged 47% (range 0–98%) for 18 sites throughout the reservoir, which was similar to experimental estimates of in situ hatching fraction of 67% for eggs in the spring and summer following their production. Based on emergence traps, neonates hatch in the field during May and June. We estimated mortality rates of 64% for resting eggs and embryos, and 59% for newly emerged neonates. Although hatching fraction saturated at the same level, eggs incubated offshore hatched later than those nearshore where water temperature was warmer and light was detectable at the sediment surface. Low dissolved oxygen concentration did not significantly reduce hatching fraction but resulted in some eggs that initiated development but failed to hatch. Collectively, our results demonstrate substantial annual turnover in the resting egg bank of B. longimanus and high mortality of resting eggs during recruitment from the egg to the first molt of the planktonic stage. These patterns suggest that propagule pressure in the form of resting eggs requires large numbers for establishment, and that considerable post-establishment resting egg production is necessary for inter-annual persistence.     

Wasp predation and wasp-induced hatching of red-eyed treefrog eggs

Eggs often suffer high levels of predation and, compared with older animals, embryos have few options available for antipredator defence. None the less, hatchlings can escape from many predators to which eggs are vulnerable. I studied early hatching as an antipredator defence of red-eyed treefrog embryos, Agalychnis callidryas, in response to egg predation by social wasps (Polybia rejecta). Red-eyed treefrogs attach their eggs to vegetation overhanging water, where they are exposed to arboreal and aerial predators. Wasps attacked half the egg clutches and killed almost a quarter of the eggs I monitored at a natural breeding site in Panama. Hatching tadpoles fall into the water, where they face aquatic predators. As predicted from improved survival of older hatchlings with aquatic predators, most undisturbed eggs hatched relatively late. However, many younger embryos directly attacked by wasps hatched immediately. Embryos attacked by wasps hatched as much as a third younger than the peak undisturbed hatching age, and most hatching embryos escaped. Thus hatching is an effective defence against wasp predation, and plasticity in hatching stage allows embryos to balance risks from stage-specific egg and larval predators. Wasp-induced hatching is behaviourally similar to the snake-induced hatching previously described in A. callidryas, but occurs in fewer eggs at a time, congruent with the scale of the risk. Individual embryos hatch in response to wasps, which take single eggs, whereas whole clutches hatch in response to snakes, which consume entire clutches. Embryos of A. callidryas thus respond appropriately to graded variation in mortality risks. Copyright 2000 The Association for the Study of Animal Behaviour.     

The influence of water and humidity on the hatching of Nematodirus battus eggs

This paper examines the influence of water on the ecology of the eggs of Nematodirus battus, with a view to estimating the importance of including rainfall in mathematical models of parasite abundance. The literature suggests that, under pasture conditions, the availability of moisture is unlikely to be limiting for egg development, while eggs and infective larvae are highly resistant to desiccation. In the presented experiment, eggs that had been kept in salt sludges at 95% and 70% RH and were subsequently put at 15°C produced only a mildly accelerated, but not a mass, hatch, in the first few days after return to water. Eggs kept at higher osmotic pressures died. Mass hatching of infective larvae, described at pasture when spells of rain follow periods of drought, is unlikely to occur as the result of a sudden water influx into eggs. Since water is not necessary for migration of infective larvae from the soil on to grass, such peaks in larval abundance are more likely to arise from the effects of temperature on hatching of eggs.     

A comparative proteomic study of the undeveloped and developed Schistosoma mansoni egg and its contents: The miracidium, hatch fluid and secretions

The schistosome egg is the key agent responsible both for transmission of the parasite from human to molluscan host, and is the primary cause of pathogenesis in schistosomiasis. Characterisation of its proteome is a crucial step in understanding the egg’s interactions with the mammalian host. We devised a scheme to isolate undeveloped eggs from mature schistosome eggs by Percoll gradient and then fractionate the mature egg into miracidial, hatch fluid and secreted protein preparations. The soluble proteins contained within the five preparations were separated by two-dimensional electrophoresis and their spot patterns compared by image analysis. Large numbers of representative spots were then excised and subjected to tandem mass spectrometry to obtain identities. In this way, the principal components of each sub-proteome were established. Chaperones were the most abundant category, with heat shock protein 70 (HSP70) dominant in the undeveloped egg and Schistosoma mansoni protein 40 (Smp-40) in the miracidium. Cytoskeletal proteins were expressed at similar levels in the undeveloped egg and miracidium, with tubulins the most abundant. The proteins of energy metabolism reflected the change from anaerobic to aerobic metabolism as the miracidium developed. None of the above categories was abundant in the hatch fluid but this peri-miracidial compartment was highly enriched for defence proteins such as thioredoxin. Hatch fluid also contained several host proteins and schistosome proteins of unknown function, highlighting its distinct nature and potentially its role. The egg secretions could not be compared with the other preparations due to their unique composition featuring the previously characterised IL-4-inducing principal of S. mansoni eggs (IPSE), Omega-1, egg secreted protein 15 (ESP15), a micro-exon gene 2 (MEG-2) protein and two members of the recently described MEG-3 family. This last preparation contains the subset of egg proteins that probably enables eggs to escape from host tissues and may also initiate granuloma formation, emphasising the need to establish fully the roles of its components in schistosome biology.     

Infection of sardine eggs by the protistan endoparasite Ichthyodinium chabelardi off Portugal

In 1997 and 1999 around 30% of the stations off Portugal sampled for sardine eggs Sardina pilchardus included eggs infected with Ichthyodinium chabelardi. A randomization test on the mean nearest neighbour distances of parasitized stations did not reveal evidence of significant spatial clustering. The mean prevalence of infection was c. 0·05 for both years, but the probability of parasite detection increased considerably with egg age. Eggs in their first day of development (before the embryo is formed) were not parasitized; most parasitized eggs were in the cohorts close to hatching. Although the reasons for age-dependent detection are unknown, if all parasitized eggs of the cohort ready to hatch were to die, infection by Ichthyodinium chabelardi would lead to mortality rates similar to those reported for the average daily mortality of sardine eggs and early larvae.