Parameters of brown-headed cowbird Molothrus ater egg discrimination in warbling vireos Vireo gilvus

We examined which egg parameters warbling vireos Vireo gilvus use to discriminate brown-headed cowbird Molothrus ater eggs and, by comparing our results to other studies, tested the prediction that ejecter species with eggs more similar in appearance to cowbird eggs will be less tolerant of foreign eggs. In addition, we tested the hypothesis that egg characteristics influence the cost of ejection and probability of committing ejection errors. Warbling vireos ejected 100% of eggs with a cowbird spot pattern and only spot pattern significantly influenced the probability of ejecting a foreign egg, whereas size and nest stage did not. Foreign eggs that differed in two parameters were not ejected significantly more than those that differed in one parameter. Thus, warbling vireos appear to be less tolerant of foreign eggs than species with eggs more divergent from cowbird eggs. There was no significant difference in the number of vireo eggs that were damaged when foreign eggs of different sizes and spot patterns were ejected, which is counter to the assumptions of the evolutionary equilibrium hypothesis. Similarly, foreign egg characteristics did not significantly influence the probability of ejection errors. Finally, egg discrimination in warbling vireos appears to have evolved directly to counter cowbird parasitism because all conspecific eggs switched into their nests were accepted.     

Egg Coloration and Recognition of Conspecific Brood Parasitism in Eastern Bluebirds

Individual eastern bluebird (Sialia sialis) females produce clutches of eggs with unique coloration and older females and females in better body condition lay more pigmented blue‐green eggs. Conspecific brood parasitism in this species is not uncommon and bluebirds occasionally reject what appear to be normal eggs by moving them to the periphery of the nest. I used UV‐visual reflectance spectrometry to objectively measure coloration of eggs and nest material. To estimate the conspicuousness of the trait, I calculated the contrast between eggs and background nest material. I found high achromatic and chromatic contrast between the coloration of eggs and of the nests, suggesting that bluebird eggs are highly conspicuous. To test the hypothesis that expression of blue‐green coloration eggs facilitates recognition of eggs laid by conspecific brood parasites, I cross‐fostered individual eggs into host nests during egg laying and monitored the fate of those eggs. I found no support, however, for the hypothesis that egg coloration facilitates discrimination of parasitic eggs from host eggs.     

新疆石河子棉蚜越冬卵的发育规律

棉蚜雌性蚜交配个体平均产卵量为 6 3± 1 1粒 ;未交配个体也产卵 ,卵亦变色 ,但卵量极少。越冬卵经 5 %NaOH浸泡 2 4h后卵壳透明 ,镜下观察可见受精卵胚胎发育到体躯分节期开始越冬。冬后胚胎发育仅处在颗粒团状的饱满卵应为无效卵 ,不会孵化 ;颜色发亮的卵处理后胚胎外貌清晰可见 ,此种卵当天即可破壳。棉蚜卵为滞育卵 ,春季降水对孵化有促进作用 ;室外棉蚜卵的饱满率和饱满卵的孵化率较低。该地区秋冬气候特点可能是石河子地区棉蚜卵低温条件下安全越冬的重要因素     

Female Mate Choice in a Paternal Brooding Blenny: The Process and Benefits of Mating with Males Tending Young Eggs

Female mate preference for males tending young offspring has been demonstrated in many fishes; however, not much is known about the choice process. Using the barred chin blenny Rhabdoblennius ellipes, a fish with male uniparental care, field experiments were conducted to investigate the female preference for males tending young eggs and then whether females choose the males with young eggs by discriminating young eggs from old eggs in the nests. Males tending young eggs (0‐ to 2‐d old) acquired new eggs nine times more frequently than those tending old eggs (3‐ to 5‐d old) regardless of other traits in males and nests. In the two egg‐switching field experiments (old to young and young to old), contrary to our expectation, male mating success was neither enhanced when given young eggs nor inhibited when given old eggs. These results suggested that females choose males with young eggs not by discriminating the developmental stage of eggs in the nests but by using other choice processes. By choosing males with young eggs, females may benefit from the dilution effects of egg predation and filial cannibalism risks and avoid male parental care failure.     

Differences in Hatching of Heterodera glycines Egg-mass and Encysted Eggs in vitro

Hatching studies with Heterodera glycines typically have been conducted with a mixture of egg-mass and encysted eggs. Laboratory research was conducted to compare hatching of H. glycines eggs from external egg masses with that of eggs extracted from within females and cysts (encysted eggs). Egg-mass eggs were collected by soaking infected soybean roots in 0.5% sodium hypochlorite, and encysted eggs were collected from females and cysts dislodged from the same roots with a stream of water. Eggs were incubated at 25 °C in deionized water, 3.0 mM ZnSO₄solution, or one of three synthetic H. glycines hatch inhibitors, mad hatched juveniles were counted every other day for 22 days. Samples of eggs collected at the beginning and end of all experiments were analyzed to determine extent of embryo development. Egg-mass eggs hatched more rapidly than encysted eggs during the first 16 days, but not thereafter. Throughout the experiments, hatch of egg-mass eggs in deionized water was greater than that of encysted eggs. From day 8 to day 22, egg-mass eggs were less sensitive than encysted eggs to the hatch inhibitor 2-(2''-carboxyethyl)-5-[carboxy(hydroxy)methylidenyl]cyclopentanone. A greater proportion of egg-mass eggs contained vermiform juveniles than did encysted eggs at the beginning of the experiments, but not at the end. Results indicated that H. glycines egg-mass and encysted eggs have different hatching behaviors that cannot be explained entirely by differences in embryological development.     

Bacterial Infection of Washed and Unwashed Eggs with Reference to Salmonellae

A survey of eggs in the Fraser Valley area of British Columbia was conducted to determine the level of bacterial contamination on washed and unwashed shell eggs and the incidence of Salmonella infection in shell eggs. Samples of eggs were taken from 15 grading stations. Determinations of eggs from 87 shipments showed that a higher proportion of eggs was heavily contaminated (>5-million organisms per egg) after washing than as received at the grading stations. This finding suggests the need for the development of more satisfactory washing procedures. No salmonellae were detected in the 180 samples (3,995 eggs) which were examined. It was concluded that Salmonella contamination of intact shell eggs does not constitute a serious health hazard in eggs from this area.     

Differences in egg size, shell thickness, pore density, pore diameter and water vapour conductance between first and second eggs of Snares Penguins Eudyptes robustus and their influence on hatching asynchrony

Brood reduction in birds is frequently induced by hatching asynchrony. Crested penguins (genus Eudyptes) are obligate brood reducers, but in contrast to most other birds, first‐laid eggs are considerably smaller in size than second‐laid eggs; furthermore, first‐laid eggs hatch after their siblings. The mechanisms underlying this reversal in size and hatching order remain unclear. In this study, we tested whether the second‐laid eggs of Snares Penguins Eudyptes robustus have a higher eggshell porosity allowing them to maintain a higher metabolic rate throughout incubation and to hatch before their first‐laid siblings. We investigated differences in egg size, shell thickness, pore density, pore diameter and water vapour conductance between first and second eggs within clutches and examined the influence of these shell characteristics on hatching asynchrony. First‐laid eggs of Snares Penguins were approximately 78% of the size of the larger second eggs. Second‐laid eggs had considerably thicker shells and more pores per cm² than first eggs, whereas pore diameter did not differ between eggs. Water vapour conductance was greater in second‐ (16.8 mg/day/torr) than in first‐laid eggs (14.9 mg/day/torr). The difference in water vapour conductance between first‐ and second‐laid eggs within clutches was related to hatching patterns. In nests where second eggs hatched before first‐laid eggs, second eggs had a considerably greater water conductance than their sibling, whereas in nests where both eggs hatched on the same day, the difference in water conductance between eggs was very small, and in a few nests where small first eggs hatched before their larger sibling, they had a greater water conductance than their larger second‐laid nestmate. Surprisingly few studies have investigated differences in shell characteristics between eggs within clutches and associated effects on hatching asynchrony. This study has demonstrated that such differences exist between eggs within clutches and that they can influence hatching patterns.     

Comparison between morphological and staining characteristics of live and dead eggs of Schistosoma mansoni

Schistosoma mansoni eggs are classified, according to morphological characteristics, as follows: viable mature and immature eggs; dead mature and immature eggs, shells and granulomas. The scope of this study was to compare the staining characteristics of different morphological types of eggs in the presence of fluorescent labels and vital dyes, aiming at differentiating live and dead eggs. The eggs were obtained from the intestines of infected mice, and put into saline 0.85%. The fluorescent labels were Hoechst 33258 and Acridine Orange + Ethidium Bromide and vital dyes (Trypan Blue 0.4% and Neutral Red 1%). When labelled with the probe Hoechst 33258, some immature eggs, morphologically considered viable, presented fluorescence (a staining characteristic detected only in dead eggs); mature eggs did not present fluorescence, and the other types of dead eggs, morphologically defined, showed fluorescence. As far as Acridine Orange + Ethidium Bromide are concerned, either the eggs considered to be live, or the dead ones, presented staining with green color, and only the hatched and motionless miracidium was stained with an orange color. Trypan Blue was not able to stain the eggs, considered to be dead but only dead miracidia which had emerged out of the shell. Neutral Red stained both live and dead eggs. Only the fluorescent Hoechst 33258 can be considered a useful tool for differentiation between dead and live eggs.     

A saltwater flotation technique to identify unincubated eggs

ABSTRACT.   Field studies on nesting birds sometimes involve questions related to nest initiation dates, length of the incubation period, or changes in parental incubation behavior during various stages of incubation. Some of this information can be best assessed when a nest is discovered before the eggs have undergone any incubation, and this has traditionally been assessed by floating eggs in freshwater. However, because the freshwater method is not particularly accurate in identifying unincubated eggs, we developed a more reliable saltwater flotation method. The saltwater method involves diluting a saturated saltwater solution with freshwater until a salt concentration is reached where unincubated eggs sink to the bottom and incubated eggs float to the surface. For Laughing Gulls ( Leucophaeus atricilla ), floating eggs in freshwater failed to identify 39.0% ( N = 251) of eggs that were subsequently found by candling to have undergone incubation prior to collection. By contrast, in a separate collection of gull eggs, no eggs that passed the saltwater test ( N = 225) were found by a later candling to have been incubated prior to collection. For Double-crested Cormorants ( Phalacrocorax auritus ), floating eggs in freshwater failed to identify 15.6% ( N = 250) of eggs that had undergone incubation prior to collection, whereas in a separate collection, none of the eggs that passed the saltwater test ( N = 85) were found by a later candling to have been incubated prior to collection. Immersion of eggs in saltwater did not affect embryo survival. Although use of the saltwater method is likely limited to colonial species and requires calibrating a saltwater solution, it is a faster and more accurate method of identifying unincubated eggs than the traditional method of floating eggs in freshwater.     

Egg transport in the coelom of the newt cynops pyrrhogaster. I. The ovulated egg is transported to the ostium by the ciliary movement of coelomic epithelial cells

We investigated the mechanism of egg transport in the newt not only by inserting various conditioned eggs into the recipient's body but also by placing them on the coelomic epithelia of the opened body cavity in the adult female newt. Most of the inserted coelomic eggs were oviposited, while 4 of 14 inserted de-jellied uterine eggs and 3 of 10 inserted de-jellied fertilized eggs were oviposited. The coelomic eggs placed on the coelomic epithelia were transported toward the ostium and entered the ostium. The de-jellied uterine eggs and the de-jellied fertilized eggs were transported to the ostium as well. Of all the eggs examined, the coelomic egg was transported the fastest. The transport speeds of coelomic eggs treated with periodic acid and the speed of boiled coelomic eggs were less than those of untreated coelomic eggs. In contrast, the transport speeds of coelomic eggs treated with trypsin and the speed of coelomic eggs removed from their vitelline envelopes (naked eggs) were faster than those of untreated coelomic eggs. Other experiments were carried out in order to ascertain the dependence of sexual activity on egg transport. The speed of coelomic egg transport in artificially sexually activated females was faster than in sexually inactive females, although the ciliary movement could always be observed in both sexually active females and sexually inactive females. This suggests that the speed of egg transport on the coelomic epithelia is controlled by the sexual activity of the female.     

A Laboratory Investigation of the Suspension,Transport, and Settling of Silver Carp Eggs Using Synthetic Surrogates

Asian carp eggs are semi-buoyant and must remain suspended in the water to survive, supported by the turbulence of the flow, until they hatch and develop the ability to swim. Analysis of the transport and dispersal patterns of Asian carp eggs will facilitate the development and implementation of control strategies to target the early life stages. Experimenting with Asian carp eggs is complicated due to practical issues of obtaining eggs in close proximity to experimental facilities and extensive handling of eggs tends to damage them. Herein, we describe laboratory experiments using styrene beads (4.85 mm diameter) as synthetic surrogate eggs to mimic the physical properties of water-hardened silver carp eggs. The first set of experiments was completed in a rectangular vertical column filled with salt water. The salinity of the water was adjusted in an iterative fashion to obtain a close approximation of the fall velocity of the styrene beads to the mean fall velocity of silver carp water-hardened eggs. The terminal fall velocity of synthetic eggs was measured using an image processing method. The second set of experiments was performed in a temperature-controlled recirculatory flume with a sediment bed. The flume was filled with salt water, and synthetic eggs were allowed to drift under different flow conditions. Drifting behavior, suspension conditions, and settling characteristics of synthetic eggs were observed. At high velocities, eggs were suspended and distributed through the water column. Eggs that touched the sediment bed were re-entrained by the flow. Eggs saltated when they touched the bed, especially at moderate velocities and with a relatively flat bed. At lower velocities, some settling of the eggs was observed. With lower velocities and a flat bed, eggs were trapped near the walls of the flume. When bedforms were present, eggs were trapped in the lee of the bedforms in addition to being trapped near the flume walls. Results of this research study provide insights about transport, suspension, and dispersion of silver carp eggs. The knowledge gained from this study is useful to characterize the critical hydrodynamic conditions of the flow at which surrogates for silver carp water-hardened eggs settle out of suspension, and provides insight into how eggs may interact with riverbed sediments and morphology.     

Functional significance of variation in egg-yolk androgens in the American coot

Maternally derived hormones in cleidoic eggs have been implicated in mediating growth, behavior, and social interactions among offspring. Given these widespread and significant effects, hormonal investments have the potential to greatly influence fitness of offspring. Intraspecific variation can exist at three levels (within individual eggs, among eggs within clutches, and among eggs from different females), each of which has different implications for offspring. We characterized all three levels of variation in maternally derived androgens (testosterone and androstenedione) present in yolks of American coot eggs. We found no variation in testosterone levels within eggs which suggests that embryos are exposed to constant androgen levels during development, and that field-based yolk biopsies are an appropriate way to sample eggs for this species. Within clutches, early-laid eggs had higher androgen levels than late-laid eggs, and this pattern may exacerbate negative effects of hatching asynchrony on chicks from late-hatching eggs if androgens provide chicks with a behavioral or growth advantage over chicks from eggs with lower androgen levels. American coots lay large clutches, and unequal resource allocation among offspring may be the optimal strategy for females with access to limited resources. Most of the variation in androgen levels occurred among eggs from different females. Females nesting on ponds with two other pairs laid eggs with significantly higher androgen levels than females living on ponds with fewer pairs. This suggests that increased territory defense behaviors influence the levels of androgens allocated to eggs and may be one mechanism underlying density-dependent effects on reproduction.     

Field Assessment of Adhesion and Hatch ofChrysoperlaEggs Mechanically Applied in Liquid Carriers

A mechanical technique was evaluated for releasing green lacewing eggs in liquid suspensions. Deposited eggs were enclosed within a circle of nonpoisonous adhesive to protect them from predation and to prevent escape of hatched larvae. Released eggs were monitored daily for 5 days after release by measuring three response variables: adhesion rate of eggs to foliage, hatch rate of eggs, and “yield” of larvae from discharged eggs; “yield” was the product of egg adhesion and egg hatch. Factors tested were: egg conditioning prior to release (incubated or refrigerated), carrier (distilled water or commercial carrier solution), application technique (mechanical or hand application), and row facing (North or South). Release technique did not significantly effect egg hatch on any day. Conditioning eggs prior to release had the greatest effect on hatch of eggs and resulting yield of larvae during the 5-day monitoring period. Carrier had a significant effect on adhesion of eggs to leaves and hatch of eggs. Commercial carrier solution increased egg adhesion but decreased egg hatch compared to water. Overall mean yield of larvae from incubated eggs distributed mechanically was not significantly different for eggs suspended in water (36.4% on day 5 post-release) and for eggs suspended in commercial carrier solution (36.1% on day 5 post-release). Hand-applied eggs had a higher hatch and subsequent yield of larvae than mechanically released eggs; however, the hand technique was labor intensive.     

Ecdysone Metabolism in Diapause Eggs and Non-Diapause Eggs of the Silkworm, Bombyx mori

In order to compare ecdysone metabolism between diapause eggs and non-diapause eggs of the silkworm, Bombyx mori, (3)H-ecdysone and its derivatives ((3)H-3-epiecdysone and (3)H-ecdysone 22-phosphate) were injected into the eggs at various stages during early embryogenesis, and the resultant labelled metabolites were analyzed by high-performance liquid chromatography. From the quantitative and qualitative changes in the labelled metabolites between diapause eggs and non-diapause eggs, it was demonstrated that epimerization of ecdysone occurred during early embryogenesis irrespective of the embryonic stage in both diapause eggs and non-diapause eggs, and that phosphorylation of ecdysone was a major metabolic step in diapause eggs, whereas dephosphorylation of ecdysone 22-phosphate and its subsequent hydroxylation at the C-20 and C-26 positions were characteristic in non-diapause eggs.     

Several workers lay eggs in the same brood cell in queenless honey bee (Apis mellifera) colonies

Queenless honey bee (Apis mellifera) colonies are often characterized by the presence of multiple eggs in brood cells. This is surprising because only one egg can be reared to maturity per cell. Moreover, worker honey bees cannot produce many eggs per day. There are several reasons that could explain the presence of multiple eggs in single cells: a) workers cannot control how many eggs they release; in this case we would expect all eggs to be from the same mother; b) excess eggs could be provided as food for the first larva to hatch in the absence of adequate brood care and this would again result in all eggs in one cell sharing the same mother; c) the number of cells available for oviposition may be limiting, obliging workers to lay eggs in cells that already contain eggs, resulting in eggs of mixed maternity. Here we show that the majority of brood cells in queenless colonies contain eggs from multiple mothers. Therefore our results suggest that the presence of multiple eggs in brood cells arises from a limitation on the number of suitable cells available for oviposition. Received 29 September 2008; revised 21 November 2008; accepted 24 November 2008.     

First cleavage of enucleated rat eggs following transplantation of karyoplast removed from pronuclear eggs stored at 2 to 6 degrees C for various durations

Pronuclear rat eggs were cultured for 24 to 48 hours at 37 degrees C after storage at 2 to 6 degrees C for 0 to 216 hours in medium. Very high proportions (89 to 97%) of eggs cleaved to the two-cell stage after storage for 0 to 48 hours. The proportion, however, decreased rapidly in eggs stored for 72 hours (60%), and eggs stored for more than 120 hours cleaved poorly. However, when male and female pronuclei from stored eggs were transplanted into enucleated fresh eggs, 92 to 100% of the fused eggs with karyoplast stored for 0 to 144 hours cleaved. Although the cleavage rate was reduced to 50% when karyoplast from eggs stored for 168 hours was transplanted, this reduction was not significant. Complete loss of cleaving ability was observed in fused eggs with the karyoplast stored for 216 hours. These results clearly indicate that the pronuclei of rat eggs can be stored for a longer period than the cytoplasm at low temperatures (2 to 6 degrees C).     

Cell Adhesion and Fusion Induced by Insemination in Zona-Free Hamster Eggs: Electrophysiological Monitoring of the Fusion Process

Cell adhesion and fusion were found to occur in zona-free hamster eggs placed in contact and then inseminated. A cytoplasmic fusion occurred in 7% of paired eggs mainly between 10 and 50 min after insemination. All other eggs that failed to fuse adhered tightly to one another within about 1 hr. Electrophysiological monitoring of the fusion process revealed that an electrical coupling (EC) suddenly appears between apposed eggs and completed within 2–15 min as the first step of cell fusion. Periodic hyperpolarizing responses (HRs), which have been found previously in fertilized hamster eggs to reflect a periodic increase in cytoplasmic Ca²⁺ ions, become gradually synchronized and completely coincide in paired eggs 10–30 min after the establishment of EC. Thus the paired eggs become an electrically single cell as the second step. Then the boundary between the eggs breaks down, resulting in formation of a single, spherical egg in several minutes. On the other hand, most of adhered eggs showed neither EC nor synchronization of HRs. Some adhered eggs showed only a low efficiency EC.     

The dependence of annulate lamellae formation on the nucleus in parthenogenetic rabbit eggs

Previously it has been shown that, in the rabbit, although annulate lamellae (AL) are absent in the follicular oocytes, they appear in the fertilized eggs after the formation of the pronuclei. Furthermore, neither pronuclei nor AL appear when unfertilized eggs are aged in vivo or in vitro. This study was undertaken to determine whether AL formation requires presence of an intact nucleus, or whether the sperm alone contains the stimulatory factors essential to AL synthesis. Rabbit eggs were exposed to 10 degrees C, then incubated for 24 hours. Control eggs were incubated without cold-treatment. Electron microscopic observations indicated that two-thirds of the eggs formed one to two 'pronuclei', or subnuclei. The remainder one-third of the cold-treated eggs and the control eggs failed to form 'pronuclei'. AL were present in large amounts only in those activated eggs (parthenogenones) which formed 'pronuceli.' AL were absent in the control and the non-activated experimental eggs, both of which failed to form a 'pronucleus.' A few small AL were observed in eggs with subnuclei. Condensed fine textured nucleoli appeared precociously during cold-treatment in some eggs and they were present in the 'pronuclei' of activated eggs. It was concluded that the sperm is not necessary for AL formation, but the presence of an intact nucleus is mandatory.     

Behavioral cues associated with oviposition by Trioza eugeniae

Trioza eugeniae oviposited significantly more eggs on Syzygium paniculatum leaves free of eggs compared to leaves with pre-existing eggs in a choice experiment, suggesting that females modify oviposition based on cues associated with the presence of eggs. In separate experiments, females avoided ovipositing on parts of leaves where eggs were present, but readily oviposited on areas of the same leaf without eggs. Epideictic pheromones are apparently not used by this species because females readily oviposited on areas of a leaf from which eggs had previously been removed. Females laid 57% of all their eggs along the margins of normal leaves, but also oviposited on artificial margins produced by cutting the leaves. The preference for natural margins over artificial margins was eliminated when the entire margin was coated with an antitranspirant compound to mask the damaged edge. These studies show that ovipositing psyllids respond both to the presence of eggs and to the suitability of the substrate.     

The white colour of the Ostrich ( Struthio camelus ) egg is a trade-off between predation and overheating

Most ground nesters lay pigmented eggs, and egg pigmentation generally matches the environment. Pigmentation of eggs has evolved as a protective device against predation, but dark-pigmented eggs can be susceptible to overheating when exposed to solar radiation. The Ostrich (Struthio camelus) lays white eggs that are unattended for the first few weeks before incubation, and are quite visible to predators. To evaluate the effect of colour on the surface and core temperatures, we painted some Ostrich eggs dark brown or white, and left some unpainted (control), and exposed all of them directly to the sun during the day. The surface and core temperatures of brown eggs were significantly higher than those of the white-painted and control eggs. In addition, the core temperature of brown eggs exceeded 37.5°C, which is the temperature at which embryo mortality starts to increase. In a second experiment, we placed eggs (brown-painted and control) in various types of vegetation to study their visibility to an observer walking towards them. The white eggs were discovered from a significantly longer distance than the brown eggs, indicating that the predation risk may be much higher for white eggs. The results thus suggest that white eggs minimise overheating and allow the Ostrich to leave its eggs unattended before incubation starts, but they are more susceptible to predation.