Unexposed Eggs Research Articles

Egg survival is reduced by grave-soil microbes in the carrion beetle, Nicrophorus vespilloides.

BackgroundNicrophorus vespilloides eggs are deposited into the soil in close proximity to the decomposing vertebrate carcasses that these insects use as an obligate resource to rear their offspring. Eggs in this environment potentially face significant risks from the bacteria that proliferate in the grave-soil environment following nutrient influx from the decomposing carcass. Our aims in this paper are twofold: first, to examine the fitness effects of grave-soil bacteria to eggs, and second, to quantify egg immunocompetence as a defence against these bacteria.ResultsOur results provide strong evidence that grave-soil microbes significantly reduce the survival of Nicrophorus eggs. Females provided with microbe rich carcasses to rear broods laid fewer eggs that were less likely to hatch than females given uncontaminated carcasses. Furthermore, we show that egg hatch success is significantly reduced by bacterial exposure. Using a split-brood design, which controlled for intrinsic differences in eggs produced by different females, we found that eggs washed free of surface-associated bacteria show increased survival compared to unwashed eggs. By contrast, eggs exposed to the entomopathogen Serratia marcescens show decreased survival compared to unexposed eggs. We next tested the immune competence of eggs under challenge from bacterial infection, and found that eggs lacked endogenous production of antimicrobial peptides, despite well-developed responses in larvae. Finally, we found that despite lacking immunity, N. vespilloides eggs produce an extraembryonic serosa, indicating that the serosa has lost its immune inducing capacity in this species.ConclusionsThe dependency on ephemeral resources might strongly select for fast developing animals. Our results suggest that Nicrophorus carrion beetles, and other species developing on ephemeral resources, face a fundamental trade-off between egg immunity and development time.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0208-x) contains supplementary material, which is available to authorized users.

Effect of exposure of ultraviolet B radiation on two anuran species, Polypedates cruciger and Duttaphrynus melanostictus under empirical conditions

Increase in ultraviolet (UV)-B radiation has been identified as a suspect in amphibian deformities and decline. Eggs of two amphibian species, Polypedates cruciger and Duttaphrynus melanostictus were exposed to UV-B radiation (312 nm) to receive erythemal dose (0.08 relative response) of the action spectra under laboratory conditions. Biologically estimated doses were calculated to match 50% (high), 25% (medium) and 10% (low) of the average daily irradiance given for the Asian region (17.92 × 10-3 Wm-2). Hatching success of the eggs and survival, growth of tadpoles and development of malformations were recorded until metamorphosis. Although the exposure had no effect on the hatching success of the eggs of the two species, the survival of tadpoles of both species was significantly reduced compared to the tadpoles coming from unexposed eggs in the control. Tadpoles of both species experienced growth retardations due to UV-B exposure. Exposed individuals were smaller at metamorphosis and they took longer to metamorphose. In addition, malformations such as ulcers, edemas, abnormally pigmented skin were common among the exposed tadpoles. Species-specific differences in the growth were observed between D. melanostictus and P. cruciger but not in the other measured parameters. This study shows that the two anuran species are highly sensitive to levels of UV-B radiation that is present in their natural environment and suffered both lethal and sub-lethal effects.DOI: http://dx.doi.org/10.4038/cjsbs.v42i2.6608 Ceylon Journal of Science (Bio. Sci.) 42(2): 45-53, 2013

Suspended sediment effects on walleye (Sander vitreus)

Environmental windows are seasonal restrictions imposed on dredging operations in the Great Lakes and other waterways of the United States. Such restrictions often generically assume that sediments resuspended by dredging result in adverse impacts to fish; this is the case in western Lake Erie where the environmental window was established due to potential impacts on walleye (Sander vitreus). To address this concern, laboratory studies mimicking sediment resuspension during dredging operations in western Lake Erie were conducted to determine whether suspended sediments affect walleye eggs and fingerlings. Newly laid eggs and 45- to 60-d old fingerlings from separate hatcheries were exposed for 72-h under flow-through conditions to 0, 100, 250, and 500mg/L total suspended sediment (TSS). Fingerlings, eggs, and newly hatched larvae were analyzed for multiple lethal and sublethal endpoints. Data indicated no significant effects of suspended sediment on egg hatch success or fingerling survival after three days of exposure. No significant differences were observed when comparing percent egg viability in the control with any TSS treatment; however, a downward trend was observed at 500mg/L. No significant differences were observed during comparisons of fingerling gill lamellae in the control with any TSS treatment; however, a statistically significant difference was observed when comparing gill lamellae in the control with the original supply animals. No significant differences were found between control means and unexposed eggs or any TSS treatment. These effect data for walleye will serve to better inform the setting of environmental windows for this species in western Lake Erie.

Lipid peroxidation was associated to the impairment of the fertilizing capability of gilthead sperm exposed to surfactants.

The present study was designed to determine whether lipid peroxidation was associated with the impairment of the fertilizing capability of gilthead sperm after acute exposure to anionic surfactant Sodium Dodecyl Sulphate (SDS). Spawned eggs and sperm were collected from adult giltheads. Sperm suspensions (100,000,000 spermatozoa/mL) were dosed separately with different concentrations of SDS (0.6, 1.5, 3 and 6 mg/L) for 60 minutes. After this period, sperm samples were randomly distributed for both outcome measurements: fertilization percentage or lipid peroxidation assessment. On one hand, exposed sperm and unexposed eggs were combined for 20 minutes during which fertilization took place. Fertilization, defined as the presence of a fertilization envelope, was assessed by microscopic observation. On the other hand lipid peroxidation on exposed gilthead sperm was determined by estimating the production of malondialdehyde (MDA). Acute exposure to SDS caused a significant inhibitory effect on fertilization success in gilthead. It also increased significantly lipid peroxidation in exposed sperm. Furthermore, a strong but negative statistical association was found between fertilizing capability and lipid peroxidation gilthead sperm exposed to SDS. Although extrapolation from the laboratory to the field requires caution, the results of this work demonstrated that the impairment of fertilization was significantly associated with lipid peroxidation induced by acute exposure to SDS. Consequently lipid peroxidation may be recommended as an early-warning bioindicator of exposure to surfactants. Further studies are required.

Choices and Consequences of Oviposition by Hylemya (Delia) Sp. (Diptera: Anthomyiidae)

Hylema sp.5females oviposit on the undersides of sepals of developing buds of both Ipomopsis aggregata and Polemonium foliosissimum. Eggs deposited on the latter are significantly more likely to be fully protected by the sepal than are eggs deposited on the former. Unexposed eggs have a significantly greater likelihood of successfully developing to the larval stage than do exposed eggs. The difference in frequency of egg exposure on the two plant species can be attributed to differences in sepal morphology: I. aggregata sepals are significantly narrower than those of P. foliosissimum. The hypothesis that females preferentially oviposit on larger flowers was unconfirmed by a manipulative choice experiment. Plants differing in the size of their flowers were potted together and presented to Hylemya in arrays in the field. Flowers of the larger-flowered pair were no more likely to be oviposited on than flowers of the smaller-flowered pair. However, there were significant negative correlations between the corolla length and the percentage of flowers laid on per day at each of two sites. There was also a significant positive correlation between the corolla width and the percentage of flowers laid on at one site. Thus females appear to be using some measure of flower morphology, or a correlated trait, in making oviposition decisions. The degree to which Hylemya is making suboptimal choices between host plant species is discussed and requires further examination.

Safety of 4-T MR imaging: study of effects on developing frog embryos.

Fertilized eggs of Rana pipiens (leopard frogs) were exposed to 0.15- or 4.5-T magnetic resonance (MR) imaging and were compared with unexposed fertilized eggs with respect to the percentage of embryos cleaving and percentage of tail buds forming normally. Similarly exposed or unexposed sperm were used to fertilize unexposed eggs, and the same parameters were observed. There was no evidence that MR imaging exposure at 0.15 or 4.5 T had any effect on cleaving embryos or tail bud formation. Since embryogenesis in amphibians is very sensitive to foreign insult, the authors conclude that exposure to a magnetic field of up to 4.5 T has no adverse effect on early development.

Acute Toxicity of Ammonia and Nitrite to Spotted Seatrout

Abstract Median lethal concentrations (LC50) of ammonia and nitrite were determined for spotted seatrout (Cynoscion nebulosus) in static tests. Ammonia toxicity tests were conducted with eggs, larvae hatched from eggs previously exposed to ammonia (ammonia-exposed eggs), larvae hatched from eggs not previously exposed to ammonia (unexposed eggs), 1-month-old juveniles, and 4-month-old juveniles. Nitrite toxicity tests were conducted with eggs and larvae. Spotted seatrout eggs were the life history stage most tolerant of un-ionized ammonia; 91.6% hatch occurred at 6.0 mg NH3-N/L. The 24-h LC50 for larvae hatched from both ammonia-exposed and unexposed eggs was 0.28 mg NH3-N/L. The 24-h LC50 of nitrite for larvae was 980 mg NO2-N/L; 92% hatch occurred at 1,200 mg NO2-N/L. Tolerance of un-ionized ammonia increased with age through the 4-month juvenile stage; the respective 24-h NH3-N LC50s for 1 - and 4-month-old juveniles were 1.38 and 1.98 mg/L, and the respective 96-h LC50s were 0.98 and 1.72 mg/L.

Temperature-Dependent Simulation of the Effects of Detrimental High Temperatures on the Survival of Mexican Bean Beetle Eggs (Coleoptera: Coccinellidae)

Eggs of the Mexican bean beetle, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae), were exposed for durations of 1/30, 1/10, 1/4, 1/2, 2, 4, 6, and 24 h to temperatures of 30, 35, 38, 40, 42, and 44°C and then were hatched at 25°C. Unexposed controls were maintained at 25°C. Survival as a percentage of that for unexposed eggs decreased with increasing exposure times at temperatures above 30°C, but developmental periods did not differ for any temperature-exposure combination at which hatch occurred. From the survival-exposure relationship for each temperature, the exposures that resulted in 90, 70, 50. 30, and 10% survival were determined, and the reciprocals of the exposures (× 100%) gave the rates of injury accumulation required to cause mortality of 10, 30, 50, 70, and 90% of the eggs, respectively. The injury accumulation rate-temperature relationships for those five mortality levels were used successfully to simulate the survival of nine egg cohorts under fluctuating temperature conditions in the greenhouse and to predict the abundance of 1st-instar larvae from observed oviposition in one soybean field.

Chick embryo development in a 26-KHz electromagnetic field.

This paper discusses an experiment designed to examine the effects of a nonionizing electromagnetic field on chick embryo development. Sixty-two test eggs were exposed for 19 days to a 26-kHz, 160-gauss peak-to-peak a-c field. Seventy unexposed eggs were maintained under the same environmental conditions as the controls. The percent of eggs hatched from the initial number was 64.5 for the exposed and 48.5 for the controls. The hypothesis that embryos in the electromagnetic field have less chance of hatching than the controls is rejected at the 5% significance level.

Effect of Intertidal Exposure on Survival and Embryonic Development of Pacific Herring Spawn

Eggs of Pacific herring were exposed to air for different periods of time to simulate tidal effects on spawn deposits at varying beach heights on the British Columbia coast. Prehatching mortality changed from 13% unexposed to 31% at 8-hr exposure twice daily. Significantly higher mortality occurred among eggs of smaller fish and eggs in smaller clumps. Incubation time decreased from 19.2 to 18.2 days with 2-hr exposure twice per day, and thereafter declined 0.4 days with greatest exposure. Larval length at hatching for unexposed eggs was 7.7 mm; lengths for all degrees of exposure were similar (7.2 mm). Larval weight was greatest (0.099 mg) for eggs exposed between 4 and 6 hr twice per day, decreasing with either greater submergence or exposure (7 and 12%, respectively). Hypoxia, desiccation, and the air-water temperature differential are considered as possible causal agents. A field survey indicated that deposition of larger eggs occurred at upper beach levels. These results suggest that a high fishing intensity could detrimentally affect future spawn and thereby reduce population recruitment.