Higher Proportion Of Eggs Research Articles

Parental Sex and Not Kinship Determines Egg Cannibalism in Arma custos Fallou (Hemiptera: Pentatomidae: Asopinae)

BackgroundArma custosFallou (Hemiptera: Asopinae) is an important predatory insect native to China, South Korea, and Mongolia. It is important to understand the evolution of egg cannibalism inA. custosto evaluate the biocontrol potential of this species. However, few reports have suggested egg cannibalism inA. custos, and whether hungry adultA. custosmales and females prey on their eggs remains unknown. Here, we investigated the effects of the parental sex ofA. custosadults on egg cannibalism of parental and non-parental eggs (kinship) under no-choice and free-choice conditions, along with the effects of predator and egg density on egg cannibalism under starvation conditions.ResultsFemales frequently visited and cannibalized a higher proportion of eggs, whereas males almost did not participate in egg cannibalism (less than 17% males showed egg cannibalism behavior). Moreover, regardless of their relationship with the egg, neither male nor female adults consumed all available eggs even in the absence of an alternative food source, and >70% of eggs remained unconsumed. In contrast, cannibalistic males and females did not discriminate between parental and non-parental egg types. Meanwhile, cannibalism rates were similar when adults were offered 30 eggs or more. However, when offered fewer than 30 eggs, cannibalism rates declined disproportionally, suggesting that limited egg availability reduced cannibalism. Additionally, the lifespan ofA. custosadult females increased significantly with increasing number of consumed eggs (p< 0.05).ConclusionArma custosfemales exhibit a higher tendency for egg cannibalism than males. Neither male or femaleA. custosdiscriminated between parental and non-parental egg types. Cannibalism enhances survival in that a starved individual who predates on eggs survives similarly to a well-fed individual. These findings provide a model to study the evolution and biological significance of egg cannibalism inA. custosand also contribute to the efficient mass rearing and realization ofA. custosfor biological control.

Breeding of the endemic Azores Woodpigeon Columba palumbus azorica: a two-year study on Pico Island

ABSTRACT Capsule The Azores Woodpigeon Columba palumbus azorica nested in low altitude forests dominated by native Morella faya, and had an extended breeding season, with high failure rates, particularly during incubation. Aims This work aimed to study the breeding phenology, nesting habitat, clutch size and nesting success of the Azores Woodpigeon. Methods Areas for nest searching were defined randomly. A total of 125 nests were monitored during two breeding seasons on Pico Island, Azores. Survival rates were calculated according to Mayfield method. Results Although most nests were found in forests dominated by introduced Pittosporum undulatum, our study highlights a strong selection for those dominated by native Morella faya. The Azores Woodpigeon seemed to avoid native Laurel forest for nesting. There was a preference for nesting in small or medium trees. Nests heights ranged between 3 and 14 m, with a mean (± se) of 7.0 ± 0.2 m. Egg laying occurred from late-February to early-August (in 2016) or to early-September (in 2017). Clutch size did not vary with time; its mean value was 1.72 ± 0.05 eggs (range: 1–2 eggs). The probability of breeding success was estimated at 0.204 ± 0.113 in 2016 and 0.152 ± 0.103 in 2017. In both years, breeding failure mostly occurred during incubation. Survival differed between the two main nesting habitats, being higher in forests dominated by Morella faya. Conclusions The Azores Woodpigeon does not seem to rely on native Laurel forest for nesting, which confirms previous results. Its preference and higher survival in another strongly threatened habitat is cause for concern. The probability of breeding success was higher than previously reported but still low. Illegal hunting of adult birds, because of alleged damages to crops, might partially explain the high proportion of eggs that did not hatch.

Foodborne infections and intoxications in Poland in 2017

The purpose of this study is to assess the epidemiological situation of food poisonings and infections in Poland in 2017. The evaluation was based on the analysis of information sent to Department of Epidemiology NIPH-NIH through ROE (pol. Rejestr Ognisk Epidemicznych)- (an electronic system created for uploading, transfer and analysis of data acquired during the outbreak investigations). Additional sources for the analysis were NIPH-NIH annual bulletins (Czarkowski MP et al. “Infectious diseases and poisonings in Poland”, 2011-2017. Warsaw, NIPH-NIH and GIS). In 2016 a total number of 926 foodborne infections and intoxications outbreaks were reported in which 27 702 persons were exposed and 7 416. A total number of 2 502 of patients were hospitalized. The most frequent etiological agent of outbreaks was hepatitis A virus (HAV) (27.1%). The most frequent cause of infection for all outbreaks cases was Salmonella sp. – 37.2%, especially serotype Enteritidis (32.2%). Among other agents rotaviruses caused 9.3% of outbreaks and noroviruses 14.5%. In 12.2% of outbreaks no etiological agent was found. The most frequent place of an outbreak was private household- 560 outbreaks (60.4%), and after that- hospital- 155 outbreaks (16.7%). In 86.8% of outbreaks no vehicle was found and in remaining the most frequent vehicle were eggs and egg products- 5.6% % of all outbreaks. Increasing yearly trend of Salmonella Enteritidis outbreaks, and high proportion of eggs and egg products as vehicles in those outbreaks point towards necessity of microbiological surveillance enchantment in relation to abovementioned products. Dynamic increase in HAV outbreaks is a good example of how a pathogen with high epidemic potential could spread in susceptible population.

Fluctuating thermal environments and time-dependent effects on fruit fly egg-hatching performance.

Organismal performance in a changing environment is dependent on temporal patterns and duration of exposure to thermal variability. We experimentally assessed the time‐dependent effects of thermal variability (i.e., patterns of thermal exposure) on the hatching performance of Drosophila melanogaster. Flies were collected in central Chile and maintained for four generations in laboratory conditions. Fourth generation eggs were acclimated to different thermal fluctuation cycles until hatching occurred. Our results show that the frequency of extreme thermal events has a significant effect on hatching success. Eggs exposed to 24 hr cycles of thermal fluctuation had a higher proportion of eggs that hatched than those acclimated to shorter (6 and 12 hr) and longer cycles (48 hr). Furthermore, eggs subjected to frequent thermal fluctuations hatched earlier than those acclimated to less frequent thermal fluctuations. Overall, we show that, egg‐to‐adult viability is dependent on the pattern of thermal fluctuations experienced during ontogeny; thus, the pattern of thermal fluctuation experienced by flies has a significant and until now unappreciated impact on fitness.

Laboratory studies on the oviposition stimuli of Culicoides stellifer (Diptera: Ceratopogonidae), a suspected vector of Orbiviruses in the United States

BackgroundBiting midges of the genus Culicoides (Diptera: Ceratopogonidae) exert a significant impact on animal agriculture worldwide because they transmit bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) to ruminants. Without effective vaccines, BTV/EHDV vector management strategies are needed, particularly in commercial white-tailed deer (WTD) facilities. However, detailed information on the ecology of midge immatures in/around cervid operations is currently lacking. Towards filling this knowledge gap, we conducted two-choice oviposition experiments with field-collected Culicoides stellifer Coquillett (a suspected vector of BTV/EHDV in the USA) under laboratory conditions to examine which natural source from the larval habitat is relatively more attractive for midge oviposition.MethodsField-collected C. stellifer females (CDC-UV light traps) were given a blood meal from live chicken and examined for their oviposition preferences for individual (or mixed) potential larval habitat oviposition stimuli in two-choice bioassays. Substrates included mud from C. stellifer habitat, mud from allopatric site, vegetation (Sphagnum spp. mosses), field water, WTD manure and de-ionized water (control).ResultsThe majority of midges (91%) oviposited in only one dish, with few females (9%) ovipositing in both the dishes. Gravid females demonstrated an overall oviposition preference for substrates with mud and vegetation from the larval habitat, depositing a significantly higher proportion of eggs on mud (52.3%) and vegetation (81.8%) than on controls (≤ 18.2%) (P ≤ 0.0320). Moreover, greater number of eggs per female were deposited on mud (29.5–40.7 depending on trial) and vegetation (38.2) than on controls (≤ 5.8). WTD manure, field water and mud from allopatric site were not found to be more attractive than controls for oviposition. Combining individual substrates (mud + WTD manure; mud + moss + WTD manure + field water) did not elicit greater oviposition responses than mud or moss alone.ConclusionsManagement strategies to discourage C. stellifer oviposition in/around commercial cervid facilities should likely focus on mud and/or vegetation, rather than WTD manure. However, further studies are needed to examine whether the spatial distributions of C. stellifer and Sphagnum spp. moss are correlated, and to determine whether targeting vegetation in/around cervid facilities can contribute to reductions in local midge densities.

Factors driving spatial variation in egg survival of an ecologically and culturally important forage fish

AbstractLow trophic‐level forage fish are experiencing global declines, influencing coupled human–ocean systems worldwide. Along the northwest coast of North America, declining trajectories of Pacific herring (Clupea pallasii) have prompted interest in improving the understanding of its population and community dynamics to better guide future conservation and management strategies.To improve future population estimates and understanding of the ecological factors governing herring egg survival, the magnitude, spatial variation and mechanisms driving herring egg loss rates were quantified. This was achieved by way of repeated observational field surveys and a predator exclusion experiment.Observational surveys revealed that regional egg loss rates (Z) were substantial and ranged from 0.101 ± 0.019 to 0.134 ± 0.028, the equivalent of 88–94% egg loss over a 21 day incubation period, or 50–60% egg loss over 6.8 days, the average time lag between spawn deposition and annual egg surveys. Furthermore, spatial variation was high, with egg loss rates varying 5‐fold among study sites. Depth, time since spawn, and spawn area were primary spatial drivers of egg loss, but predator abundance and exposure were secondarily important.Experimental evidence showed that benthic predation and habitat type were strong drivers of egg loss, suggesting that a high proportion of eggs, particularly those spawned on benthic substrates, are consumed by predators.These results have important conservation implications for managers and ecologists seeking to estimate herring biomass and to understand the environmental influences on predator–prey interactions that affect herring dynamics.

Molecular epidemiology and pathology of spirorchiid infection in green sea turtles (Chelonia mydas).

Spirorchiid blood fluke infections affect endangered turtle populations globally, and are reported as a common cause of mortality in Queensland green sea turtles. Both the flukes and their ova are pathogenic and can contribute to the stranding or death of their host. Of particular interest are ova-associated brain lesions, which have been associated with host neurological deficits. Accurate estimations of disease frequency and the relative effect of infection relating to different spirorchiid species are made difficult by challenges in morphological identification of adults of some genera, and a lack of species-level identifying features for ova. A new specifically designed molecular assay was used to detect and identify cryptic spirorchiids and their ova in Queensland green sea turtle tissues collected from 2011 to 2014 in order to investigate epidemiology, tissue tropisms and pathology. Eight spirorchiid genotypes were detected in 14 distinct tissues, including multiple tissues for each. We found no evidence of a characteristic pathway of the eggs to the exterior; instead the results suggest that a high proportion of eggs become lost in dead-end tissues. The most common lesions observed were granulomas affecting most organs with varying severity, followed by arteritis and thrombi in the great vessels. The number of spirorchiid types detected increased with the presence and severity of granulomatous lesions. However, compared with other organs the brain showed relatively low levels of spirorchiid diversity. An inverse relationship between host age and spirorchiid diversity was evident for the liver and kidneys, but no such relationship was evident for other organs. Molecular data in this study, the first of its kind, provides the first species-level examination of spirorchiid ova and associated pathology, and paves the way for the future development of targeted ante-mortem diagnosis of spirorchiidiasis.

Effects of variation in nest curtain design on pre-laying behaviour of domestic hens

Laying hens in loose-housing systems select a nest daily in which to lay their eggs among many identical looking nests, they often prefer corner nests. We investigated whether heterogeneity in nest curtain appearance – via colours and symbols – would influence nest selection and result in an even distribution of eggs among nests.We studied pre-laying behaviour in groups of 30 LSL hens across two consecutive trials with eight groups per trial. Half of the groups had access to six identical rollaway group-nests, while the others had access to six nests of the same type differing in outer appearance. Three colours (red, green, yellow) and three black symbols (cross, circle, rectangle) were used to create three different nest curtain designs per pen. Nest position and the side of entrance to the pens were changed at 28 and 30 weeks of age, respectively, whereby the order of changes was counterbalanced across trials. Nest positions were numbered 1–6, with nest position 1 representing the nest closest to the pen entrance. Eggs were counted per nest daily from week of age 18 to 33. Nest visits were recorded individually with an RFID system for the first 5h of light throughout weeks 24–33.Hens with access to nests differing in curtain appearance entered fewer nests daily than hens with identical nests throughout the study but both groups entered more nests with increasing age. We found no other evidence that curtain appearance affected nest choice and hens were inconsistent in their daily nest selection. A high proportion of eggs were laid in corner nests especially during the first three weeks of lay. The number of visits per egg depended upon nest position and age: it increased with age and was higher after the nest position change than before in nest position 1, whereas it stayed stable over time in nest position 6. At 24 weeks of age, gregarious nest visits (hens visiting an occupied nest when there was at least one unoccupied nest) and solitary nest visits (hens visiting an unoccupied nest when there was at least one occupied nest) accounted for a similar amount of nest visits, however, after the door switch, gregarious nest visits made up more than half of all nest visits, while the number of solitary nest visits had decreased. The visual cues were too subtle or inadequate for hens to develop individual preferences while nest position, entrance side, age and nest occupancy affected the quantity and type of nest visits.

Seasonal Trends in the Social Composition and Inside-Trunk Distribution ofKalotermes flavicollis(Isoptera: Kalotermitidae) Colonizing Grapevines

The polyphagous drywood termite Kalotermes flavicollis (Fabricius) can establish its colonies inside living trees, causing a progressive debilitation that ends with the death of the plant. For this reason, it is considered one of the major pests of Sherry vineyards in Andalusia, SW Spain. To analyze the trends of colonization of this termite, a detailed investigation was performed during 16 mo in seven districts of the Sherry area, cutting randomly selected grapevine trunks into six sections, from which all individuals were collected and counted according to their developmental instar or caste. The results detected variations in the social composition of the groups colonizing grapevines according to the spatial distribution inside the vine trunk and in the numerical trends over the seasons. A pattern of seasonal migrations of the termites inside the trunk was inferred, with upward movements from spring to autumn and downward movements from autumn to winter. During winter, when termites were mainly located in the medium-basal sections of the trunk, a higher proportion of eggs and larvae was detected. Going from spring to summer, when the majority of the termites was located in the medium-upper sections of the trunk, there was an increase of nymphal instars followed, during autumn, by the appearance of alates, mostly located in the upper sections of the grapevine. Pseudergates and reproductives maintained their proportions and locations almost unchanged during the year.

Storage Time and Eggshell Colour of Pheasant Eggs vs. the Number of Blastodermal Cells and Hatchability Results

The aim of this study was to investigate the number of the embryo blastodermal cells and hatchability of pheasant from eggs of different eggshell colours depending on the length of the storage period before hatching. On the day of collection, dark-brown and olive eggs were characterised by a similar and significantly higher (by about 48%) number of embryo BCs in comparison with light-brown and blue eggs. Dark-brown eggs stored longer than one day had the highest, while blue-shelled eggs the lowest, number of BCs. The number of BCs found in eggs with blue and light-brown coloured eggshells stored for 10 days was similar and significantly lower (by 27.7%) in comparison with dark-brown eggs. With the lengthening of the storage period, the number of blastodermal cells in eggs of all eggshell colours declined as a result of necrobiosis. In comparison with the dark-brown and olive-shelled eggs, eggs with blue eggshells had higher (by about 7.0%) weight loss during the 21 days until hatching. The dark-brown and olive eggs were found to have a 10.3% higher proportion of eggs considered as fertilised in comparison with the blue-shelled eggs. Eggs with dark-brown shells stored for 2-4 days prior to hatching, in comparison with blue-shelled eggs, had a higher proportion of fertilised eggs. The dark-brown and olive eggs stored for 7 and more days before hatching possessed a higher value of this trait in comparison with the eggs of light-brown and blue eggshells (x = 80.9 against 66.4%). The highest drop in the share of fertilised eggs, which amounted on average to 3.25% for each day of storage, was observed in the blue-shelled eggs. The dark-brown eggs stored for 7 days before being placed in an incubator had higher hatchability from fertilised eggs (by 17.8%) in comparison with the eggs with blue eggshells. In the case of eggs stored for 8 to 10 days, values for this trait were higher for the dark-brown and olive-coloured eggs than for the blue-shelled eggs. The highest mean decrease of chick hatchability from fertilised eggs was observed in the case of the blue-shelled eggs (7.93% for each day). The dark-brown eggs had significantly higher (by about 22.0%) chick hatchability from fertilised eggs than the blue-shelled eggs. Moreover, the dark-brown and olive eggs, in comparison with the blue-shelled eggs, were characterised by a significantly higher hatchability after each period of storage before incubation. The highest negative trend-cycle was observed for eggs with blue shells, while the smallest--for olive-shelled eggs. Directly after laying, pheasant eggs differed with regard to the developmental advancement of the blastodermal embryo depending on eggshell colour. Longer storage time caused the numbers of blastodermal cells in eggs to decrease. The group with blue shells had a lower proportion of fertilised eggs and lower hatching results than the dark-brown eggshell group. It was also demonstrated that the value of hatchability indices decreased significantly irrespective of eggshell colour after seven days of storage prior to hatching.

Experience-Induced Habituation and Preference Towards Non-Host Plant Odors in Ovipositing Females of a Moth

In phytophagous insects, experience can increase positive responses towards non-host plant extracts or induce oviposition on non-host plants, but the underlying chemical and behavioral mechanisms are poorly understood. By using the diamondback moth, Plutella xylostella, its host plant Chinese cabbage, and a non-host plant Chrysanthemum morifolium, as a model system, we observed the experience-altered olfactory responses of ovipositing females towards volatiles of the non-host plant, volatiles of pure chemicals (p-cymene and alpha-terpinene) found in the non-host plant, and volatiles of host plants treated with these chemicals. We assessed the experience-altered oviposition preference towards host plants treated with p-cymene. Naive females showed aversion to the odors of the non-host plant, the pure chemicals, and the pure chemical-treated host plants. In contrast, experienced females either became attracted by these non-host odors or were no longer repelled by these odors. Similarly, naive females laid a significantly lower proportion of eggs on pure chemical-treated host plants than on untreated host plants, but experienced females laid a similar or higher proportion of eggs on pure chemical-treated host plants compared to untreated host plants. Chemical analysis indicated that application of the non-host pure chemicals on Chinese cabbage induced emissions of volatiles by this host plant. We conclude that induced preference for previously repellent compounds is a major mechanism that leads to behavioral changes of this moth towards non-host plants or their extracts.

Inhibition of MEK or cdc2 Kinase Parthenogenetically Activates Mouse Eggs and Yields the Same Phenotypes as Mos−/− Parthenogenotes

Mammalian eggs are arrested in metaphase II of meiosis until fertilization. Arrest is maintained by cytostatic factor (CSF) activity, which is dependent on the MOS–MEK–MAPK pathway. Inhibition of MEK1/2 with a specific inhibitor, U0126, parthenogenetically activated mouse eggs, producing phenotypes similar to Mos−/− parthenogenotes (premature, unequal cleavages and large polar bodies). U0126 inactivated MAPK in eggs within 1 h, in contrast to the 5 h required after fertilization, while the time course of MPF inactivation was similar in U0126-activated and fertilized eggs. We also found that inactivation of MPF by the cdc2 kinase inhibitor roscovitine induced parthenogenetic activation. Inactivation of MPF by roscovitine resulted in the subsequent inactivation of MAPK with a time course similar to that following fertilization. Notably, roscovitine also produced some Mos−/−-like phenotypes, indistinguishable from U0126 parthenogenotes. Simultaneous inhibition of both MPF and MAPK in eggs treated with roscovitine and U0126 produced a very high proportion of eggs with the more severe phenotype. These findings confirm that MEK is a required component of CSF in mammalian eggs and imply that the sequential inactivation of MPF followed by MAPK inactivation is required for normal spindle function and polar body emission.

Effects of Corn Plants and Corn Pollen on Monarch Butterfly (Lepidoptera: Danaidae) Oviposition Behavior

The oviposition behavior of adult insects can have a major impact on the level of exposure of their offspring to natural and artificial toxins. Pollen from Bt-corn hybrids represents a novel toxin and very little is known regarding its detection and possible avoidance by ovipositing females. The effect of corn plant proximity and corn pollen presence on the oviposition behavior of the monarch butterfly, Danaus plexippus (L.), was assessed in cage and flight chamber studies. The proportions of monarch eggs oviposited on milkweed plants dusted pollen from with a Bt-corn hybrid, an untransformed hybrid, gravel dust, and undusted control plants were recorded from a cage study. None of the treatments differed significantly in the relative proportion of eggs found. The effect of Bt and untransformed corn plant proximity and corn pollen presence was also assessed in a flight chamber. A significantly higher proportion of eggs (96%) were recovered from patches of milkweed plants not surrounded by corn plants, and a significantly higher proportion of eggs (nearly 70%) were recovered from patches of milkweed plants not dusted with corn pollen. There were no significant differences in the effects of Bt corn plants or corn pollen compared with untransformed plants or pollen. These results may have important implications for the level of exposure of monarch larvae to Bt-corn pollen.

Trichogramma egg parasitism of Helicoverpa armigera on pigeonpea and sorghum in southern India

Abstract Trichogramma spp. (Hymenoptera: Trichogrammatidae) only rarely parasitize eggs of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on pigeonpea (Cajanus cajan (L.) Millspaugh), while on other plants including sorghum (Sorghum bicolor (L.)) high parasitism levels of this host are found. In this study two strategies designed to increase the parasitoid activity on pigeonpea were tested in the field: intercropping pigeonpea with sorghum and mass‐releasing T. chilonis Ishii. Neither strategy led to an increase in parasitism. On pigeonpea, H. armigera oviposited >74.8% of its eggs on calyxes and pods. Parasitism levels in host eggs collected from different plant structures varied significantly with 3.6, 0.3, and 40.7% of eggs on calyxes, pods, and leaves parasitized. Earlier studies have shown that calyxes and pods possess long glandular and non‐glandular trichomes, and are covered by sticky trichome exudates which inhibit parasitoid searching behaviour. Parasitism levels between 27.9 and 100% were recorded from host eggs on the intercropped sorghum. Trichogramma chilonis was the dominant parasitoid species. The mean clutch size was 2.03, but up to six parasitoids emerged per egg. Progeny sex ratio (% females) decreased with clutch size, from 63.1% at a clutch size of one to 46.0% at a clutch size of five. Sticky trap catches showed that while the parasitoid population in sorghum increased when H. armigera started ovipositing, the population within pigeonpea did not benefit from either a high parasitoid population in sorghum or a high host egg density on pigeonpea. During one of five seasons studied, however, high parasitism levels (up to 73%) were recorded on pigeonpea. During this season, H. armigera oviposited on pigeonpea plants in the vegetative growth stage and a high proportion of eggs were collected from leaves. Parasitism levels were positively correlated with the percentage of eggs collected from leaves. This study shows that the parasitization efficiency of Trichogramma spp. on pigeonpea depends mainly on the location of the host eggs. This explains why parasitism levels of H. armigera eggs on pigeonpea did not increase when intercropped with sorghum or after mass‐releasing T. chilonis.

The influence of temperature on egg mortality in the budmoth Zeiraphera diniana (Lepidoptera: Tortricidae), and its role in determining the regional abundance of an important forest pest

AbstractThe range of the moth Zeiraphera diniana Guénée and the regions where high population densities are infrequent and unpredictable are thought to be determined by high temperatures during egg pre-diapause. Exposure of eggs to incubation temperatures known to be optimal for Z. diniana elsewhere resulted in a pre-diapause mortality of 13% which corresponds to known rates of egg mortality in British forests. Evidence suggests that high temperature and its duration are both important determinants of pre-diapause egg mortality which, if experienced in forest conditions, may prevent populations from reaching outbreak levels. Historical records of outbreaks were associated with lower than average August temperature. However, high temperatures on their own are unlikely to determine the range of the insect in Britain since a high proportion of eggs survives extremes; more than 70% of British eggs survived 24 h exposure to a temperature of 30°C. Variations in egg mortality among families of moths suggests a genetic basis for differences in thermal tolerance. Furthermore, there may be selection for thermally-tolerant eggs in British forest environments and this could be connected with other forms of genetic differentiation in budmoth populations.

Oviposition site selection in three species of European Newts (Salamandridae) genus Triturus

AbstractOviposition site selection in Triturus helveticus, T. alpestris and T. cristatus was studied both in natural and laboratory situations. In a natural breeding site, eggs of the three species were not laid equally on several plants: T. cristatus laid practically all their egges on only one plant (Nasturtium officinale) while T. helveticus eggs were collected on four plant species. In laboratory experiments, plastic and cotton fabric supports made it possible to test ovipositing female selectivity according to flexibility and shape of support and egg-laying distance below the surface. In all three species, a high proportion of eggs were laid on supports of linear shape (as opposed to arborescent shape) and egg frequency decreased as a function of depth (from 0 to 40 cm below the surface). Selection according to flexibility was also observed, the smallest species (T. helveticus) laying more eggs on the thinner supports. The role of support selectivity during oviposition in Triturus is discussed, in term of proximate (i.e. female protection against predators, breathing necessity) and ultimate (i.e. egg survival) factors, and related to new ecology.

Effects of photoperiod and intermittent lighting on reproduction in pheasant hens

Forty 28-wk-old ring-necked pheasant hens were equally distributed among 5 treatment groups and exposed to the following light schedules for 36 wk: Treatment 1 - 16L:8D; Treatment 2 - 1L:11D:4L:8D; Treatment 3 - 1L:13D:2L:8D; Treatment 4 - 1L:14D:1L:8D; and Treatment 5 - 1L:14.5D:0.5L:8D. The number of days from stimulatory lighting to the first egg was significantly (P<0.05) greater under the intermittent schedules (20.3, 29.5, 40.3, 44.4, and 57.7 d, respectively) when the subjective daylength was shorter than 13 h. Despite the delay in initiation of laying, average egg production was higher under intermittent lighting (23.0, 36.0, 48.6, 43.8, and 42.3% or 58.0, 93.0, 122.5, 110.4, and 106.6 eggs). Patterns of oviposition indicated a tendency in the birds exposed to intermittent lighting to have synchronized laying, with the period opposite the longest scotoperiod provided by their light schedule; thus subjective daylengths of 13, 11, 10 and 9.5 h, respectively, were created. Fertility was significantly (P<0.05) lower under intermittent lighting and was apparently associated with a high proportion of eggs in the late stages of oviducal development at the time of insemination.

Shell strength of eggs from medium‐bodied hybrid hens housed in cages or on range in outside pens

Abstract 1. On average, over the laying year, a higher proportion of eggs were cracked from cages (4.6%) than from range (2.0%); the difference tended to increase as the flocks aged. 2. There was evidence that eggs from range had stronger shells: they required more energy to crack, shell thickness was greater and shell deformation at 70 weeks was less (though the difference was not significant). 3. The differences between systems in shell strength, although real, were small. It is probable that environmental insults make a much larger contribution than shell strength to differences in crack incidence. 4. Eggs laid by hens on range were larger (+ 6.8% at 36 weeks and + 2.9% at 70 weeks) than those laid by the same stock housed in cages.

Observations on the hatching and activation of fresh Taenia saginata eggs.

A method is described for the hatching and activation of Taenia saginata eggs. All proglottids collected from eight naturally-infected people in Kenya contained a high proportion of eggs with oncospheres that could be activated. A mean activation rate of 82.7% was recorded in eggs aged ten hours to ten days. Bile, in the absence of pancreatic enzymes, stimulated activation of T. saginata oncospheres but trypsin was necessary to achieve hatching from the oncospheral membrane.

Influence of extracellular Ca 2+ and Mg 2+ ions on the second meiotic division of mouse oocytes: Relevance to obtaining haploid and diploid parthenogenetic embryos

The types of mouse parthenogenones obtained in a medium modified with respect to Ca 2+ and/or Mg 2+ ions were investigated in “spontaneously” activating eggs after culturing cumulus masses in vitro for 5 hr. The second meiotic division was affected in eggs cultured in medium lacking Ca 2+ and Mg 2+ or Ca 2+ alone, resulting in suppression of second polar body extrusion in a high proportion of cases, giving rise to two pronuclear eggs or eggs that underwent immediate cleavage. Extrusion of the second polar body occurred normally when the cumulus mass was cultured in complete medium and, in a high proportion of eggs, when Mg 2+ alone was lacking in the medium. The results are discussed with reference to the second meiotic division. The method provides an efficient way for obtaining a large number of different types of parthenogenetic embryos.