Blood platelets and schistosome egg excretion

The eggs of helminths of the Schistosoma genus require to be extravasated in order to continue the life cycle of the parasite. The possible mode by which this takes place was investigated in a mouse model. Suppression of platelet activity in Schistosoma mansoni-infected mice by administering rabbit anti-mouse platelet serum or a selection of "antiplatelet drugs" resulted in a significant reduction of parasite egg excretion. This reduction was best achieved when antiplatelet agents were administered just before the onset of parasite egg excretion. The association between parasite eggs and platelets was illustrated in vivo and in vitro where platelet aggregates on egg surfaces were seen in both light and electron microscopy. In addition, eggs that had been isolated from infected mouse tissues induced platelet aggregation in whole mouse blood, and this was inhibited by preincubation with the beta-lactam antibiotic, ticarcillin. Isolated eggs were also capable of inducing ex vivo platelet aggregation in mice, which was dependent on presensitization with eggs. These data suggest a role for platelets in the extravasation and excretion of parasite eggs in schistosomiasis.     

Response to re-infection with Brachylaima cribbi in immunocompetent and immunodeficient mice

The course of infection in C57BL/6J mice re-infected with Brachylaima cribbi was assessed by comparing faecal egg excretion of re-infected mice with age- and sex-matched mice receiving a primary infection only. For both male and female mice there was a significant reduction in the mean number of eggs per gram of faeces at the peak of infection 4 weeks after the challenge infection compared with mice receiving a primary infection only. There was no significant difference in the duration of the infection. This experiment was repeated using age-matched male mice but on this occasion all mice were killed and dissected 4 weeks after the challenge infection and mean eggs per gram of faeces, worm burden and fecundity determined. There was no significant difference in the worm burdens of the re-infected mice compared with age-matched animals receiving a primary infection only. However, there were significant differences in the mean faecal eggs per gram and worm fecundity with the challenge infection group having lower egg counts and reduced fecundity. An enzyme-linked immunosorbent assay using whole worm antigens was developed and used to determine mouse anti-B. cribbi serum antibody levels during the course of infection. Anti-B. cribbi serum antibody absorbance ratios increased six- to sevenfold by 4 weeks after a primary infection beyond which a constant level was maintained. The course of challenge infection in non-obese diabetic severe combined immunodeficient mice showed no significant differences in egg excretion, worm burden or fecundity when primary and challenge infections were compared. These results indicate that the immune response invoked by a previous B. cribbi infection in immunocompetent mice affects fecundity but does not affect the establishment or duration of infection.     

In vivo and in vitro egg production by Nematospiroides dubius during primary and challenge infections in resistant and susceptible strains of mice

Experiments were conducted to examine adult worm burdens, fecal egg output, and in vitro fecundity of Nematospiroides dubius in resistant LAF1 and susceptible CBA mice 12, 15, 18, and 21 days following primary and challenge infections. A strong correlation was obtained on the number of eggs produced by worms cultured in vitro and the egg production as assessed by fecal egg count. Worm counts, fecal egg counts, and in vitro fecundity were similar on all days studied following a primary infection in both mouse strains. However, after challenge infection, LAF1 mice showed lower worm burdens, fecal egg output, and in vitro egg production when compared to CBA mice. Although the egg production of surviving female worms from immune LAF1 mice was decreased, it never fell below a threshold of 100 eggs/day. The reduced fecundity may be a manifestation of a general anti-worm response rather than responses directed specifically at worm reproduction.     

Parasitological and morphological study of Schistosoma mansoni and diabetes mellitus in mice

Schistosomes are blood-dwelling flukes which are highly dependent on the host metabolism. The aim of this study was to investigate possible relationship between streptozotocin-induced diabetes and the outcome of acute murine schistosomiasis mansoni. Male and female SW mice were treated by a single intraperitoneally injected dose of streptozotocin (180 mg/kg). Seven days after induction, both control and diabetic animals were infected with 70 Schistosoma mansoni cercariae (BH strain). Diabetics and their controls were weighed 45 days after birth and for the last time prior to killing. Susceptibility to infection was evaluated twice a week by quantifying fecal egg excretion 7–9 weeks post-infection by the Kato–Katz’ thick smear method. Mice were euthanized the day after the last fecal examination was performed. Adult worms were recovered from the portal system and mesenteric veins, whereas liver and intestine were removed for enumeration of egg load. No differences in worm length or in measurements of the reproductive organs, tegument, and suckers were detected. Also oviposition was unaffected as the total number of eggs per female worm from the liver, the small and the large intestine was the same in both groups. An oogram evaluation revealed a lower percentage of mature (23.0% vs. 40.7%) and a higher percentage of immature (69.1% vs. 51.7%) eggs in the small intestine of the diabetic mice. We suggest that principally a hampered egg passage through the intestine tissue caused this reduction and that probably both the eggs and the impaired host response play a role.     

Schistosoma mansoni: control of hepatotoxicity and egg excretion by immune serum in infected immunosuppressed mice is schistosome species-specific, but not S. mansoni strain-specific.

Immunosuppressed mice infected with Schistosoma mansoni suffer from an acute hepatotoxicity reaction, and they fail to excrete as many parasite eggs as comparably infected immunologically intact control animals. The hepatotoxicity was shown here to be preventable, and egg excretion rates were enhanced, by transfer of serum from donors with chronic S. mansoni infections, but not by serum from donors with heterologous infections of Schistosoma haematobium, Schistosoma bovis, or Schistosoma japonicum. The effects of the transferred sera are considered to be due to specific antibody, but the possibility of cytokine involvement is discussed. A high degree of serological cross-reactivity was found between sera from mice infected with the different schistosome species and unfractionated egg homogenate (SEA) in ELISA. Cross-reactivity of the heterologous sera was, however, reduced against CEF6, a partially purified fraction of S. mansoni eggs that contains the putative hepatotoxin and has serodiagnostic potential. S. mansoni isolates from Puerto Rico, Brazil, Egypt, and Kenya shared similar characteristics with respect to the immune dependence of egg excretion and hepatotoxicity in immunosuppressed mice. The S. mansoni geographic isolates were also indistinguishable serologically, in terms of both the capacity of respective infection sera to neutralize hepatotoxicity and in their capacity to promote egg excretion of the other isolates in vivo. Complete immunological cross-reactivity of the geographically distinct isolates was also observed in ELISA with both CEF6 and SEA. Utilization of CEF6 for serodiagnosis of schistosomiasis mansoni is therefore unlikely to be restricted by geographical considerations.     

The effects of constant and changing temperatures on the period from egg hatching to egg laying in Tanymastix stagnalis

The main duration of time from egg hatching to egg laying (D) in this anostracan crustacean increases at lower constant temperatures. The mean number of eggs per female lay between 25 and 50. In both regularly changing temperature experiments D was significantly increased (P<.05). This may be due to an increase in length of adult life which would also account for the increase in number of eggs per female to about 100. The relation of the results to the life and survival strategy of the animal in Ireland in discussed.     

Ovarian dynamics, egg size, and egg number in relation to temperature and mating status in a butterfly

Although the temperature‐size rule, that is, an increase in egg (and body) size at lower temperatures, applies almost universally to ectotherms, the developmental mechanisms underlying this consistent pattern of phenotypic plasticity are hitherto unknown. By investigating ovarian dynamics and reproductive output in the tropical butterfly Bicyclus anynana (Butler) (Lepidoptera: Nymphalidae: Satyrinae) in relation to oviposition temperature and mating status, we tested the relevance of several competing hypotheses for temperature‐mediated variation in egg size and number. As expected, females ovipositing at a lower temperature laid fewer but larger eggs than those ovipositing at a higher temperature. Despite pronounced differences in egg‐laying rates, oocyte numbers were equal across temperatures at any given time, while oocyte size increased at the lower temperature. In contrast, there were greatly reduced oocyte numbers in mated compared to virgin females. Our results indicated that temperature‐mediated plasticity in egg size cannot be explained by reduced costs of somatic maintenance at lower temperatures, enabling the allocation of more resources to reproduction (reproductive investment was higher at the higher temperature). Furthermore, there was no indication for delayed oviposition (no accumulation of oocytes at the lower temperature, in contrast to virgin females). Rather, low temperatures greatly reduced the oocyte production (i.e., differentiation) rate and prolonged egg‐maturation time, causing low egg‐laying rates. Our data thus suggested that oocyte growth is less sensitive to temperature than oocyte production, resulting in a lower number of larger eggs at lower temperatures.     

Tolerization of mice to Schistosoma mansoni egg antigens causes elevated type 1 and diminished type 2 cytokine responses and increased mortality in acute infection

The granuloma that surrounds the Schistosoma mansoni egg is the cause of pathology in murine schistosomiasis, and its formation is driven by egg Ag-stimulated type 1 and type 2 cytokines. To determine the role of egg-driven immune responses during schistosome infection we rendered CBA/Ca mice unresponsive to schistosome eggs by combined cyclophosphamide treatment and thymectomy. In the early acute stages of schistosome infection, egg-tolerized mice suffered high mortalities. Granuloma size and deposition of collagen in the liver were significantly reduced in egg-tolerized mice. Similarly, limited granuloma responses were detected in the intestines of these mice, and this was associated with a >90% reduction in egg excretion. Histologically, egg-tolerized mice had exacerbated hepatocyte damage, with extensive microvesicular steatosis. Elevated plasma transaminase levels confirmed the damage to hepatocytes. Infected egg-tolerized mice had impaired proliferation responses to egg Ag but intact responses to worm Ag. Tolerized mice had diminished Ab responses to egg Ag and had a type 1 cytokine isotype pattern to worm Ag, with elevated IgG2a and diminished IgG1 and IgE. Egg-tolerized mice failed to down-regulate type 1 cytokines that are normally elicited during early schistosome infection. Hepatic granuloma cells from egg-tolerized mice were also type 1 cytokine dominated, with elevated frequencies of Tc1/Th1 and reduced Tc2/Th2 cells. This study demonstrates that mice tolerized to schistosome eggs have elevated type 1 cytokine responses with diminished type 2 responses and reduced anti-egg Ab during schistosome infection, and these effects are detrimental to the host.     

Distribution ofChilo partellus (Lepidoptera: Pyralidae) egg batches on maize

Distribution ofChilo partellus egg masses was studied in field, greenhouse, and laboratory experiments. The eggs were laid in batches mainly on the lower side and the lower leaves of the plant. The egg batch size ranged from 1 to 169 eggs, with a median of 33.5 eggs per batch (average, 40.5). Oviposition ofC. partellus is described at two levels. The first level, choice of oviposition plants, followed a random distribution. The second level, number of egg batches per plant, followed an aggregated distribution in the field, where more than one egg batch was deposited on the same plant by the same female, which was found on 25% of the oviposition plants. A mechanism for egg-layingC. partellus females to perceive preceding oviposition or injured plants could not be detected. Oviposition site choice seemed to be mediated by tactile stimuli.     

Experimental manipulation of female reproduction reveals an intraspecific egg size-clutch size trade-off

A negative relationship, or trade-off, between egg size and clutch size is a central and long-standing component of life-history theory, yet there is little empirical evidence for such a trade-off, especially at the intraspecific level. Here, I show that female zebra finches (Taeniopygia guttata) treated chronically during egg formation with the anti-oestrogen tamoxifen lay smaller eggs (by 8%) but produce larger clutches (on average two eggs more) than controls. Decreased egg mass in tamoxifen-treated females was associated with a 50% decrease in plasma levels of the two yolk precursors, vitellogenin and very-low-density lipoprotein. Although tamoxifen-treated females laid more, smaller eggs (and had a higher total expenditure in their clutch), they did not differ from controls in the number of chicks fledged, the mass or size of these chicks at fledging, or the chicks' egg-production performance at three months of age. However, tamoxifen-treated females had lower relative hatching success: they laid more eggs but hatched the same number of chicks. Among individual tamoxifen-treated females, birds that laid the smallest eggs early in their laying sequence laid the largest number of additional eggs, that is, there was a negative correlation, or trade-off, between egg size and clutch size.     

Egg and time limitation mediate an egg protection strategy

The number of mature eggs remaining in the ovaries and the time left for oviposition determine the reproductive decisions of the hyperdiverse guild of insects that require discrete and potentially limiting resources for oviposition (such as seeds, fruits or other insects). A female may run out of eggs before all available oviposition sites are used (egg limitation), or die before using all of her eggs (time limitation). Females are predicted to change clutch size depending on whether eggs or time is the limiting resource. We extend this framework and ask whether the same constraints influence a strategy in which females modify eggs into protective shields. In response to egg parasitism cues, female seed beetles (Mimosestes amicus) lay eggs in vertical groups of 2–4, modifying the top 1–3 eggs into shields in order to protect the bottom egg from attack by parasitoids. We made contrasting predictions of how egg and time limitation would influence egg size and the incidence and level of egg protection. By varying access to seed pods, we manipulated the number of remaining eggs a female had at the time she received a parasitism cue. Although egg size was not affected, our results confirm that egg‐limited females protected fewer eggs and time‐limited females protected more eggs. Female body size explained the number of eggs in a stack rather than host deprivation or the timing of parasitoid exposure. Our results clearly show that host availability relative to female age influences the incidence of egg protection in M. amicus. Furthermore, our study represents a novel use of life history theory to explain patterns in an unusual but compelling defensive behaviour.     

The Schistosoma haematobium egg granuloma

The etiology of the granulomatous response around Schistosoma haematobium eggs in mice was investigated. Eggs injected into the microvasculature of the lungs of mice evoked a granulomatous reaction which was demonstrated at 8 and 16 days. Prior exposure of mice to the eggs or to crude soluble egg antigens (SEA) resulted in significantly larger granulomas than in the unsensitized controls. The degree of sensitization was dependent both on the route of administration and the quantity of eggs. Furthermore, this phenomenon could be adoptively transferred with spleen cells from previously sensitized mice but not with serum. Mice sensitized with S. haematobium eggs and challenged by injection of SEA into their footpads developed both immediate and delayed swelling. Cross-sensitization between S. haematobium, S. mansoni and S. japonicum eggs was also studied in both the lung and footpad systems.     

Lifetime egg production and egg mortality in the damselflyPyrrhosoma nymphula (Sulzer) (Zygoptera: Coenagrionidae)

Artificial oviposition sites were used to estimate egg deposition rates in the field. Females laid an average of 10.76 eggs/minute with a mean duration of 22.81 minutes, giving an average clutch size of 245 eggs. Since one mating corresponded to one clutch of eggs, lifetime mating success was used as a measure of the number of clutches produced. Mean lifetime clutch production was 5.91 clutches per female, equating to 1447 eggs per female per lifetime. Eggs were hatched in the laboratory at temperatures comparable with those in the field. Hatching was highly synchronised and the overall hatching success was 75.1%. Causes of egg mortality in the laboratory were limited to infertility and unhatchability. Since no other sources of egg mortality could be found at the study site, this value was a good reflection of hatching success in the field. Lifetime egg production and hatching success were used to estimate the number of viable offspring produced per female, giving a higher order estimate of reproductive success than has previously been published for a zygopteran.     

Body-size effect on egg size in eublepharid geckos (Squamata: Eublepharidae), lizards with invariant clutch size: negative allometry for egg size in ectotherms is not universal

Within a single clutch, smaller species of ectotherms generally lay a smaller number of relatively larger eggs than do larger species. Many hypotheses explaining both the interspecific negative allometry in egg size and egg size–number trade-off postulate the existence of an upper limit to the egg size of larger species. Specifically, in lizards, large eggs of large species could have too long a duration of incubation, or they could be too large to pass through the pelvic opening, which is presumably constrained mechanically in larger species. Alternatively, negative allometry could be a result of limits affecting eggs of smaller species. Under the latter concept, hatchling size in smaller species may be close to the lower limit imposed by ecological interactions or physiological processes, and therefore smaller species have to invest in relatively larger offspring. Contrary to these lower limit hypotheses, explanations based on the existence of an upper limit always predict negative egg-size allometry even in animals with invariant clutch size, in which naturally there is no egg size–number trade-off. We studied egg-size allometry in lizards of the family Eublepharidae, a monophyletic group of primitive geckos with large variance in body size and an invariant number of two eggs per clutch. We found an isometric relationship between egg and female size that does not support the upper limit hypotheses.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 527–532.     

Reinfection and recidive in Hymenolepis nana infections (author's transl)]

The excretion of Hymenolepis nana eggs begins in CF-1 mice between the 11th and 12th day irrespective of the wormload. In Swiss mice, however, the onset of egg excretion can be retarded up to the 15th day if the number of parasites is high. The re-appearance of eggs after treatment occurs between the 6th and 9th day using an exact diagnostic method. If the number of parasites is low, than re-appearance of eggs occurs later than if it is high. An infection with eggs protects mice for several months against a re-infection with eggs but not against one with cysticercoids. If cysticercoids are used to establish the primary infection no immune reaction against a re-infection develops. If eggs reappear in the faeces after treatment then the following conclusion can be drawn: Eggs reappear within a week after treatment then it must be a relapse. Eggs reappear during the second week then it can be either a relapse or a re-infection. Eggs reappear at three weeks or later then it can only be due to a re-infection.     

一种估算草地贪夜蛾卵块中卵粒数量的简易方法

草地贪夜蛾Spodoptera frugiperda (Smith)是2019年发现入侵我国的一种重要的外来害虫,对我国粮食种植业造成严重威胁。明确虫情是做好草地贪夜蛾预测预报和制定科学防控策略基础。在田间调查中需要一种简便、快速估计落卵量的方法,以明确田间虫口数量。本研究在实验室条件下收集草地贪夜蛾雌虫产于玉米叶片上的卵块,记录了每个卵块的长、宽、层数和卵粒数量,获得了卵块面积,建立了卵粒数量与卵块面积的指数函数模型：Y=e(2.1596×0.00832X),并依据该模型提出了根据卵块面积测算卵粒数量的分级表。该方法为田间调查中卵块卵粒数量量的快速估计提供了参考。     

The evolution of egg clustering in butterflies: A test of the egg desiccation hypothesis

Females of many insect species cluster their eggs. Egg clustering by lepidopteran species usually results in aggregation of larvae that are more often conspicuously coloured and apparently distasteful or unpalatable than larvae of solitary species. While the costs and benefits of aggregation in terms of larval survival and growth are well documented, the evolutionary ecology of egg clustering has been long debated and is still unresolved. We tested the egg desiccation hypothesis, first proposed by Stamp (1980), which to our knowledge has never been examined experimentally. The egg desiccation hypothesis proposes that egg clustering is adaptive per se (i.e. increases fitness of females) by reducing egg mortality via desiccation.We tested this hypothesis for the Nymphalid butterfly, Chlosyne lacinia, an egg-clustering species on its sunflower host plant, Helianthus annuus. We first documented natural variation in batch size for this butterfly. We then tested experimentally hatch success of varying batch sizes and egg-layering arrangements under controlled humidity levels. Hatch success was positively related to relative humidity. Eggs in larger groups with greater number of layers had greater hatch success than smaller, monolayered egg batches, especially when relative humidity was low. Our results indicate that, not only number of eggs, but also the arrangement (i.e. layering and density), increase batch survival by protecting eggs from desiccation. However, despite increased hatch success in dense, multilayered clusters, we found wide variation in layering and density in natural populations of C. lacinia. This variation is probably maintained by trade-offs in egg survival, such as increased cannibalism of eggs by siblings, in dense clusters. Nevertheless, protection from egg desiccation provides an alternative explanation for the origin and maintenance of egg clustering in lepidopterans and possibly other insects. The pattern of egg deposition in the Nymphalidae supports this hypothesis, since most North American species cluster their eggs tightly, whereas most species in tropical regions lay eggs singly or in loose monolayers.     

Influence of egg predation and physical disturbance on lake trout Salvelinus namaycush egg mortality and implications for life-history theory

The influence of egg predators and physical disturbance on lake trout Salvelinus namaycush egg mortality was investigated in situ in Lake Michigan where recruitment is below detectable levels and egg predator abundance is high. Comparisons were made with Lake Champlain where recruitment is low and egg predator abundance is also low and with Parry Sound (Lake Huron) where recruitment is moderate and egg predators are in low abundance. A multi-density egg seeding method (100 to 5000 eggs m⁻²) was used to quantify the effect of physical disturbance and egg predation on egg loss. Wind fetch was used as an index of physical disturbance and comparisons across all locations and egg densities suggested that at sites with high wind fetch (>5 km), physical disturbance may be a greater source of egg loss than predation. When analyses were limited to those sites having a wind fetch of <5 km, the percentage of eggs recovered was found to be linearly related to predator density. The strength of this relationship was based largely on egg recovery at 500 and 1000 eggs m⁻² because recovery at lower (100, 250 eggs m⁻²) and very high (5000 eggs m⁻²) densities was not significantly related to predator density. The reason for this is probably that at low egg densities, crayfish Orconectes spp., the major egg predator at most sites, had difficulty finding and consuming eggs and at high egg densities they became satiated. Egg loss was directly related to wind fetch for Lake Michigan and on average six-fold greater than for Parry Sound suggesting that without corresponding changes in fecundity and age structure, lake trout populations in large lakes like Lake Michigan are inherently less productive than those from enclosed inland waters.     

Field oviposition rates and egg load dynamics of pollen beetles (Meligethes aeneus Fab.) (Colepotera: Nitidulidae)

Abstract 1 Egg loads from field collected pollen beetles (Meligethes aeneus Fab., Coleoptera: Nitidulidae) were determined by dissecting beetles caught at the beginning and end of the putative daily oviposition period. Field collected beetles were offered Brassica napus (L.) plants in cages for 8 (morning and early afternoon), 16 (overnight), and 24 h to ascertain the number of eggs laid during these time periods. 2 Most eggs were laid in the morning and early afternoon. The proportion of gravid females was higher at the beginning of the oviposition period than at the end. Most females in the morning carried two eggs, whereas one egg was more common in the afternoon. 3 We hypothesized that the number of eggs laid during the oviposition period would be equivalent to the difference between egg loads at the beginning and end of oviposition. This was not the case; differences in egg loads were significantly lower than number of eggs laid. However, the number of eggs laid was equivalent to the egg load at the beginning of the oviposition period, suggesting that eggs available in the morning are laid during the following day. 4 Population estimates of daily oviposition rates, approximately 0.7 eggs per beetle and day, were close to estimates from laboratory studies when the proportion of gravid females was taken into consideration.     

Effect of egg storage duration and egg turning during storage on egg quality and hatching of broiler hatching eggs

In commercial hatcheries, it is common to store eggs before incubation. One practice to improve hatchability consists in egg turning during this storage. This work aims to highlight the effects of turning on the physicochemical aspects of eggs and, consequently, how this turning can influence the hatching of chicks. An experiment was conducted to evaluate the effects of storage duration and egg turning during storage on egg quality, hatchability, and residual analysis. A total of 7 500 hatching eggs were collected from a 55-week-old commercial Cobb500 breeder flock and storage according to the treatments. The experiment was completely randomized in a 3 × 2 factorial design with three storage periods (4, 8, and 12 days) and egg turning (180° turn of eggs once a day) or no turning during storage, totaling six treatments. Regardless of turning, eggs stored for 4 days weighed more than turned eggs stored for 8 and 12 days, which were similar (P < 0.05). Non-turned eggs experienced an increase in relative shell weight with increased storage duration, and non-turned eggs stored for 4 and 8 days differed from non-turned eggs stored for 12 days (P < 0.05). Albumen pH of turned eggs stored for 4 and 8 days was lower than that of non-turned eggs stored for the same durations (P < 0.05). Albumen pH of turned eggs increased as storage duration increased (P < 0.05). Egg turning increased hatching by 2.02% over that of non-turning (P < 0.05). Eggs stored for 12 days, irrespective of turning, had higher late embryonic mortality (P < 0.05) compared to the other treatments. It was concluded that turning eggs during pre-incubation storage was adequate to improve hatchability of fertile eggs. Storing fertile eggs for 12 days is harmful to egg quality and increases embryo mortality even if eggs were turned.