Impairment of reproduction in the red flour beetle, Tribolium castaneum (Herbst) (Col., Tenebrionidae) due to larval feeding on triflumuron-treated diet

The larvae of Tribolium castaneum (Herbst) of different ages were exposed to various concentrations viz., 0.0001, 0.001 and 0.01 ppm of triflumuron up to pupation. The adults were allowed to feed on untreated diet. The preoviposition period, fecundity, egg viability and incubation period of the eggs laid were studied. Triflumuron significantly lengthened the preoviposition and incubation periods (P < 0.001). Fecundity and egg viability were also reduced (P < 0.001) due to the treatment. Both the strains were affected by the treatment.     

Changes of uridine permeability during the maturation of tunicate eggs.

The time course of uridine uptake by eggs and embryos of the tunicate Ascidia callosa was studied using 5-min pulses of [³H]uridine at intervals from the unfertilized egg to the 16-cell embryo. The unfertilized egg is permeable to uridine, but 5 min after fertilization uptake begins to drop, reaching a minimum of 30% of the unfertilized rate about 30 min after fertilization. At 45 min after fertilization, permeability begins to increase, reaching a plateau about 3 hr after fertilization at the two-cell stage. The initial decrease in permeability occurs at first polar body production; the increase at 45 min is coincident with the formation of the second polar body. Substrate concentration experiments up to 200 μM show strict concentration dependence for uridine uptake. The inhibitors p-chloromercuribenzoate (PCMB), dinitrophenol (DNP), and thymidine have little, if any effect on permeability. Cold (?1°C) and Na⁺-free sea water inhibit uptake 60% during all three developmental stages. The changes in permeability may be indicative of temporary reorganization of the plasma membrane during the fertilization-initiated completion of meiosis.     

Thymidine kinase activation in unfertilized sea urchin eggs by homogenization and fertilization

Kinetics of in vivo phosphorylation of ³H-thymidine taken up by sea urchin eggs was compared between unfertilized and fertilized eggs. The percentage of phosphorylated ³H-thymidine in the total acid-soluble radioactivity in the cell increased with increasing incubation time within the first several minutes of incubation in the unfertilized eggs, while nearly 100% of phosphorylation of thymidine was observed without regards to the incubation time and in spite of a tremendous increase in the net uptake of thymidine in the fertilized eggs, suggesting possible activation of thymidine kinase occurring soon after fertilization.In contrast to the in vivo finding, the thymidine kinase activity in unfertilized egg homogenates was found in general to be almost as large as that in fertilized egg homogenates. However, when the enzyme activity was assayed within a short period (30 min) after homogenization of unfertilized eggs, the activity was found to increase more or less with time after homogenization, reaching a level equal to that in fertilized egg homogenates. This enzyme activation after homogenization was especially marked in case of Pseudocentrotus eggs and sometimes amounted to a several fold increase.Preliminary investigations revealed possible involvement of some redox reaction(s) in the thymidine kinase activation during and/or after homogenization of unfertilized sea urchin eggs.     

Mapping of quantitative trait loci affecting eggshell quality on chromosome 9 in an F2 intercross between two chicken lines divergently selected for eggshell strength

Broken and cracked eggshells are major causes of significant economic losses to the egg production industry. The quantitative trait loci (QTL) on chromosome 9 influencing the quality of eggshells were identified by analysing an intercross between two parent lines developed from the same founder population by a two-way selection for eggshell strength with non-destructive deformation conducted over 14 generations. Chromosome-wide highly significant ( P  <   0.01) QTL associated with egg weight (EW), short length of egg (SLE), long length of egg (LLE) and eggshell weight were mapped to the distal region of chromosome 9. Among the QTL affecting EW, SLE and LLE, ovocalyxin-32 was identified as a potential candidate gene influencing eggshell traits. Marker-assisted selection based on these QTL could be used to develop strategies for reducing the breakage and cracking of eggs in commercial layer houses.     

Structure and function of the hydropyle of the egg of the bug, Sphaerodema molestum

Changes in the wet weight, dry weight, and volume of the egg of Sphaerodema molestum during embryonic development have been studied. Also, experiments have been carried out to ascertain the route of entry of water from the environment into the egg.During development the eggs considerably increase their volume and wet weight while their dry weight progressively decreases. When the eggs of S. molestum are incubated in dye solutions, the latter penetrate through the chorionic hydropyle and reach the outer surface of the serosal hydropyle. This indicates that water enters in significant quantity through the chorionic and serosal hydropyles. The behaviour of 48-hr-old experimental eggs of S. molestum, in which the entry of water is blocked, further confirms that the intake of water is effected only through the hydropyles. The significance of the uptake of water in the eggs is discussed in relation to protein metabolism during embryogenesis.     

Adult female crickets, Gryllus texensis, maintain reproductive output after repeated immune challenges

Abstract.  Both immunity and reproduction are thought to be energetically costly and therefore likely to make trade-offs with one another. To assess whether increasing immune system activity results in a decline in egg production, the immune system in the cricket Gryllus texensis is activated over a period of 12 days with regular injections of lipopolysaccharide (LPS) derived from Serratia marcescens , and the number of eggs laid during this time counted. Egg quality is also assessed by measuring total protein of eggs laid, fertilization and hatching success, and the weight of individual eggs laid after the series of injections. Indirect evidence suggests that LPS induces an immune response in G. texensis . However, the number of eggs produced is not affected. There is also no effect of repeated LPS injections on female weight, egg protein content, or fertilization and hatching success. Taken together, these results suggest that with food and water provided ad libitum , females can protect many aspects of fitness in the face of increased immune system activity. However, there is some evidence to suggest that large (100 μg) doses of LPS lead to reduced female longevity, and also in egg weight that could affect offspring success. Although the possibility exists that the decline in lifespan and egg weight after high-dose injections reflects a trade-off between reproduction and immune investment, another possibility is that these doses yield nonspecific effects, or that the high-dose induces an overwhelming immune response that leads to self-damage.     

Effect of weight and storage time of broiler breeders’ eggs on morphology and biochemical features of eggs,embryogenesis, hatchability,and chick quality

The transfer of hatchability results obtained under experimental conditions to the commercial ground with a positive financial effect proves the value and usefulness of these data. On the other hand, finding results on commercial processes of broiler breeders’ egg incubation in the literature is challenging. The presented study aimed to determine the effects of egg weight and storage time on the physical, biochemical characteristics of hatching eggs, embryogenesis and hatchability in Ross 308 broiler breeders. On the laying day, the eggs were divided into four weight groups: S – small eggs (57–61 g), M – medium eggs (62–66 g), L – large eggs (67–71 g), and XL – extra-large eggs (72–76 g). The eggs were then stored for 3, 7, 14, and 21 days under controlled conditions. As the egg storage time increased, a decrease in the yolk quality (lower index) was observed. The highest Haugh units were found in eggs from the S and M groups. The cholesterol content of the M, L, and XL groups was lower on days 7, 14, and 21 as compared to that of eggs only stored for 3 days. Egg weight loss during incubation decreased with an increase in the egg weight. An extension of the egg storage time caused an increase in the loss of egg weight. On the 14th and 18th days of hatching, an increase in the eggshell temperature was noted with an increase in the weight of the egg. The eggs stored for 7 days were characterised by the highest shell temperature on each day. The highest hatchability percentage was recorded for the M group. The hatchability rate decreased with the prolongation of the storage time, while the number of crippled chicks after hatching increased. The results confirmed that the increased weight of the eggs and prolonged storage time (14 and 21 days) increased the weight and decreased the length of the newly hatched chicks, respectively. Chicks from the heaviest eggs and those stored for 14 and 21 days showed poor results on the Pasgar score® test. The observations indicate the need to adopt various (of those available) methods to assess the quality of newly hatched chicks in hatcheries in order to produce high-quality broiler chickens. The results also indicate that prolonged egg storing beyond 14 days may affect the thyroid hormone economy during the hatching of chicks, especially in the XL group.     

Does saltwater flushing reduce viability of diapausing eggs in ship ballast sediment?

Flushing of ballast tanks with seawater has been proposed to reduce the risk of invasion associated with residual ballast in 'no ballast on board' ships. The efficacy of this procedure, however, has not been determined. Using diapausing eggs isolated from ballast sediments — as well as from Lake Erie sediment — this study investigated the impact of salinity (0, 8 and 35‰) and temperature (10, 20 and 30 °C) on the cumulative abundance and species richness of hatched zooplankton taxa. The rate and amount of hatching varied dramatically between sediments and across salinity–temperature regimes. Although exposure to saline water inhibited emergence of freshwater taxa during the exposure phase of all trials, mixed results were evident after diapausing eggs were returned to freshwater. The efficacy of salinity as a ballast treatment method was temperature dependent, although the direction of the effect was case-specific. Exposure of eggs to saline water was less effective at 10 and 30 °C than at 20 °C. Although flushing ballast tanks with open ocean water is expected to significantly reduce the number of active invertebrates living in residual ballast water (a potentially larger source of invaders), our results indicate that the most effective treatment conditions for reduction of diapausing egg viability is 8‰ salinity at 20 °C.     

Does solitary incubation enhance egg water uptake and offspring quality in a lizard that produces single-egg clutches?

Many organisms invariably produce one offspring per reproductive bout, but experimental tests of adaptive explanations for this reproductive pattern are rare. To address this issue, we studied a lizard (Anolis sagrei) that produces one egg at a time to test the hypothesis that solitary incubation (due to single-egg clutches) eliminates competition with adjacent eggs for moisture and thus enhances offspring quality via increased egg water uptake during development. Our findings suggest that solitary incubation does not affect rates of moisture uptake by eggs or offspring size. However, egg moisture uptake and offspring size were negatively affected when eggs were adjacent to an egg that died during development. Depending on rates of infertile eggs or embryo mortality in the field, single-egg clutches may improve developmental environments and enhance offspring fitness. These results highlight the importance of considering the role of plastic embryonic responses during development in explaining reproductive patterns.     

Regulation of ooplasmic sodium and potassium activities in developing locust eggs

Ooplasmic activities of potassium and sodium were measured with ion sensitive microelectrodes before and during the period of maximal water uptake which occurs 3–5 days after oviposition for eggs incubated at 37°C. Potassium activity increased from 84 mM in eggs before fertilization at 118 mM in eggs 1 day after fertilization (d1). Sodium activity increased from 8 mM to 29 mM over the same period. These changes exceeded those predicted from the decrease in water content (8%) during the first day after oviposition. Between d1 and d3, potassium and sodium activities decreased to values predicted on the basis of the 88% increase in egg water content. Although water content increased an additional 46% between d3 and d5, ooplasmic sodium activity remained constant at 11 mM and potassium activity increased from 64 mM to 74 mM during this time. Declines in concentrations of sodium and potassium measured in whole eggs by atomic absorption spectrometry mirrored the increase in egg water content. The results suggest that regulation of ooplasmic sodium and potassium activities is accomplished by release of these ions from internal stores, possibly the york spheres. © 1992 Wiley-Liss, Inc.     

Mouse sperm capacitation assessed by kinetics and morphology of fertilization in vitro

Epididymal mouse spermatozoa were preincubated for periods of 5-120 min and then tested for their ability to penetrate freshly ovulated eggs synchronously and rapidly. When zona-intact eggs were used, only suspensions preincubated for 120 min gave consistently high rates of fertilization, but suspensions preincubated for 30 min were functionally equivalent to those incubated for 120 min when used with zona-free eggs; the only major observable differences were a 15-min lag in sperm-egg interaction and an increased incidence of asynchrony with multiple sperm penetrations. A morphological study of sperm-egg interactions using zona-intact eggs indicated that, within 35 min of gamete mixing, egg microvilli could be detected by SEM in association with the fertilizing sperm head. Using conventional light microscopic examination of fixed and stained preparations, initial stages of sperm head decondensation could be detected in the majority of eggs after 45-60 min and the process was essentially completed, with the egg at the telophase-second polar body stage of meiosis II, after 75 min. Similar kinetics were observed with sperm concentrations of 10(5) and 10(6)/ml. The time required for penetration by capacitated sperm suspensions is therefore relatively short and the most accurate information regarding state of capacitation and rate of sperm penetration can be obtained by choosing an appropriately short interval for sperm-egg interaction before assessment.     

Geographical and seasonal gradients in hatching failure in Eastern Bluebirds Sialia sialis reinforce clutch size trends

Eggs untended during the laying phase can lose viability if exposed to high temperatures, such as those common at lower latitudes and late in the nesting season. The egg‐viability hypothesis states that constraints on viability during the laying phase could account for latitudinal and seasonal gradients in clutch size. We used 7 years’ worth of data collected by volunteers (The Birdhouse Network, co‐ordinated by the Cornell Laboratory of Ornithology) to look simultaneously at populations across the temperate breeding range of Eastern Bluebirds Sialia sialis in order to test three predictions of the egg‐viability hypothesis: the probability of hatching failure decreases at higher latitude and increases later in the season, and that these trends are strongest among large clutches. The overall average number of unhatched eggs relative to the total number of eggs laid was similar to that found by other studies (7.8%; range 6.8–8.9% annually; n = 32 567 eggs from 7231 nests from 530 study sites). Using generalized linear mixed models that controlled for the non‐independence of eggs within a clutch, we found that the ‘per‐egg’ probability of hatching failure was highest late in the season, highest at lower latitudes, and highest for both small (three‐egg) and large (six‐egg) clutches. The seasonal and geographical gradients in egg hatching failure reinforce documented seasonal and geographical trends in clutch size. Loss of egg viability prior to incubation currently provides the most parsimonious and consistent explanation of the observed patterns of hatching failure. However, alternative explanations for large‐scale patterns, particularly those not consistent with the egg‐viability hypothesis, warrant further research into other causes of hatching failure, such as microbes and infertility (related to extra‐pair mating). Our results demonstrate that investigating causes of variation in demography among local populations across a geographical gradient provides a potential means of identifying selection pressures on life‐history traits.     

Hydropy and ultrastructure of egg envelopes in Aleochara bilineata (Coleoptera, Staphylinidae)

Aleochara bilineata oviposits in soil microhabitats likely to contain the dipteran pupae that are hosts of its ectoparasitoid first instar larvae. The eggs of A. bilineata have a rigid chorion but they are nonetheless hydropic and, after 30 h of development, start to increase in volume and do so until 50 h. This increase in volume is due to absorption of water. The eggs increase their initial volume by a factor of 1.68 that corresponds to an increase of 44.44% of initial weight. To explain this augmentation in volume, we describe the modifications occurring in the egg chorion during hydropy. The increase in volume in such a rigid egg is made possible through the fragmentation of the chorion which, initially dense and regular, becomes fragmented. Such adaptation enables female A. bilineata to oviposit hydropic eggs in habitats where mechanical resistance is needed. Accepted: 29 October 2000     

Effect of Cytochalasin B on the Development of Membrane Transports in Sea Urchin Eggs after Fertilization

Investigations were made on the role of the cytoskeleton in the onset of ionic events following fertilization of sea urchin eggs. Events which depend upon phosphoinositide metabolism, such as the cortical reantion and acid release are affected by cytochalasin B (CB) after fertilization but not after activation of eggs with the ionophore A23187. These findings suggest that the sequence of events following sperm-egg attachment depends on the cytoskeleton. CB also inhibits the Na⁺ pump and alanine uptake when added before insemination and during the following 30 min. These results argue for a role of the egg cortex cytoskeleton in activation of the Na⁺ pump by fertilization. We propose that the inhibitory effect of CB on the development of amino-acid uptake after fertilization may result from an increase in the Na⁺ content of the egg resulting from Na⁺ pump suppression rather than from direct blockage of the carrier.     

Uptake of Ca2+ is one of the earliest responses to fertilization of sea urchin eggs

Sea urchin eggs take up Ca for 10 min following insemination (determined as uptake of 45Ca from the SW (3)). Although 90% of this uptake occurs after the beginning of the cortical reaction and may represent external binding of Ca to the egg surface coats, there is a brief phase of uptake (o-30 sec) which precedes the cortical reaction; this may represent a Ca flux into the eggs.     

Intraspecific variation in desiccation survival time of Aedes aegypti (L.) mosquito eggs of Australian origin

Aedes aegypti (L.) mosquitoes preferentially oviposit in natural and artificial receptacles where their eggs are able to withstand drying as water levels fluctuate. Desiccation‐resistant eggs also increase the potential for establishment in non‐native habitats while providing logistical impediments to control programs. Viability and mean survival times of eggs stored under three dryness conditions for up to 367 days were investigated among three field‐derived colonies of Australian Ae. aegypti to understand variation in desiccation survival. Further investigations compared egg survival between an established colony and its wild counterpart. Our results confirmed that Ae. aegypti eggs can withstand desiccation for extended periods of time with approximately 2–15% egg viability recorded after one year and viability remaining above 88% under all conditions through 56 days. Intraspecific variations in egg survival times were recorded, suggesting local adaptation while each of the colonies demonstrated a consistent preference for higher humidity. Egg volume varied between the populations, suggesting a relationship between egg volume and survival time, with the marginally larger eggs (Charters Towers and Innisfail) having greater desiccation resistance over the range of conditions. The strong survivorship of Charters Towers eggs in dry, warm conditions demonstrates the adaptive significance of a desiccation‐resistant egg.     

Comparison of the physical properties of real and artificial salmonid eggs and of their performance when drifting in an experimental stream channel

The paper compares three batches of brown trout (Salmo trutta Linnaeus) eggs, two batches of Atlantic salmon (Salmo salar Linnaeus) eggs and the artificial trout eggs described by Ottaway (1981), in terms of their measurable physical characteristics. Attention was given to the effects of temperature and of the stage of development of the real eggs. Comparisons were also made between brown trout eggs and artificial eggs of the rate of fall in a water column, of the value and speed of attainment of terminal velocity when falling through water and of the pattern of settlement within an experimental stream channel.The main measurable characteristics of brown trout eggs (after water hardening) and of artificial eggs (values in parentheses) were: diameter 0.52–0.54 mm (0.54), fresh weight 0.078–0.086 g (0.09), density 1.071–1.075 g ml^–1 (1.066), and volume 0.073–0.081 ml (0.085). There was no evidence of any major change in these values as egg development proceeded. Salmon eggs had a similar density to trout and artificial eggs but had 30 to 70% greater weight and volume. The water-hardening of eggs caused their dry matter content to fall from 37–39% to 31–34% and there were corresponding increases in volume and fresh weight.The rate of fall of trout eggs and artificial eggs through water when timed from rest at the water surface to a depth of 125 cm was similar for both types of egg at 10 °C. This rate rose with increasing temperature at the same low rate of c. 0.02 cm s^–1 °C^–1 for both types of egg. Both types of egg had a terminal velocity of c. 8.8 cm s^–1 and both achieved terminal velocity in less than 1.5 s after release.The patterns of settlement of the two types of eggs in an experimental channel were similar.     

The cooling time of fertile chicken eggs at different stages of incubation

We asked whether or not the thermal characteristics of fertile avian eggs changed throughout incubation. The cooling and warming times, expressed by the time constant τ of the egg temperature response to a rapid change in ambient temperature, were measured in fertile chicken eggs at early (E7), intermediate (E11) and late (E20) stages of embryonic development. Same measurements were conducted on eggs emptied of their content and refilled with water by various amounts. The results indicated that (1) the τ of a freshly laid egg was ~50 min; (2) τ decreased linearly with the drop in egg water volume; (3) the dry eggshell had almost no thermal resistance but its wet inner membrane contributed about one-third to the stability of egg temperature; (4) the egg constituents (yolk, albumen and embryonic tissues) and the chorioallantoic circulation had no measurable effect on τ; (5) the presence of an air pocket equivalent in volume to the air cell of fertile eggs reduced τ by about 3 min (E7), 5 min (E11) and 11 min (E20). Hence, in response to warming the egg τ at E20 was slightly shorter than at E7. In response to cooling, the egg τ at E20 was similar to, or longer than, E7 because embryonic thermogenesis (evaluated by measurements of oxygen consumption during cold) offset the reduction in τ introduced by the air cell. In conclusion, until the onset of thermogenesis the thermal behavior of a fertile egg is closely approximated by that of a water-filled egg with an air volume equivalent to the air cell. It is possible to estimate the cooling τ of avian eggs of different species from their weight and incubation time.     

Calcium pools in sea urchin eggs: roles of endoplasmic reticulum and mitochondria in relation to fertilization.

A preparation of sea urchin eggs permeabilized with digitonin (40 microM for 2.5 min) was used to study the kinetic characteristics of the two cellular compartments suspected to play a key role in cellular calcium transfer during fertilization: an ATP-dependent Ca2+ pool (Km = 0.47 microM; Vm = 0.48 nmol/min.mg protein) probably located in the endoplasmic reticulum and a mitochondrial Ca2+ pool (Km = 1.50 microM; Vm = 0.12 nmol/min.mg protein). Fertilization triggered a decrease in the rate of ATP dependent uptake by the non-mitochondrial pool (Km = 0.59 microM; Vm = 0.15 nmol/min.mg protein) while it transiently increased the Ca2+ uptake into mitochondria (2 min post-fertilization: Km = 2.20 microM; Vm = 0.40 nmol/min.mg protein). Microanalysis studies performed on quickly frozen, freeze substituted and embedded eggs showed a transient Ca2+ enrichment of mitochondria soon after fertilization thus suggesting that mitochondria behave as a Ca2+ sink at fertilization. Results are discussed in relation to the role of endoplasmic reticulum and mitochondria in handling free calcium during the early period following sea urchin egg fertilization.     

Cytological changes and DNA and protein synthesis in parthenogenetically activated sea urchin eggs

Summary The present study deals with cytological observations, DNA and protein synthesis in artificially activated sea urchin eggs. The eggs were activated by means of Loeb's double treatment with butyric acid and hypertonic sea water. Most of the eggs ofHemicentrotus pulcherrimus divided when the chromosomes duplicated after formation of the first monaster and other eggs divided at a later cell cycle. In the eggs ofTemnopleurus toreumaticus, however, haploid division at the first cell cycle was observed predominantly.Activated eggs that were treated for 25 min with hypertonic sea water showed a marked uptake of³H-thymidine during the two periods of 30–40 min and 90–100 min after the double treatment. These periodic changes in the³H-thymidine uptake paralleled morphological changes within the nucleus. However, these periods of increased uptake were not observed in the eggs treated with hypertonic sea water for 60 min. During exposure to hypertonic sea water, the³H-thymidine-uptake by eggs activated with butyric acid decreased gradually. When the uptake of¹⁴C-valine by eggs was measured, a very low level was seen in unfertilized eggs. The level of uptake increased strikingly when the eggs were activated with butyric acid but was suppressed by the hypertonic treatment. However, removal of the eggs to sea water allowed the uptake to return to the former high level. This pattern suggests that the hypertonic treatment has an inhibitory effect on the synthesis of protein (or enzymes) which obstruct cleavage induction.