In vitro rearing of Edovum puttleri, an egg parasitoid of the Colorado potato beetle – development from egg through the pupal stage

A variety of semi-defined artificial diets were developed and tested for their ability to support the in vitro development of Edovum puttleri. In the most effective diet, 2.6% of E. puttleri pupated. This diet contained high levels of hen egg yolk combined with Manduca sexta larval hemolymph, or with a mixture of M. sexta egg homogenate and larval hemolymph. Egg homogenate alone (without the addition of hemolymph) was not capable of supporting the parasitoid's development. Thus, hemolymph appears to contain unidentified factor(s) important for inducing pupation of the wasp. Addition of M. sexta pupal fat body tissue extract (in place of hemolymph) also promoted pupation of E. puttleri. Gypsy moth (Lymantria dispar) larval hemolymph could not replace M. sexta larval hemolymph. Fractionation irreversibly reduced the growth-promoting effects of M. sexta larval hemolymph. However, the most effective fraction contained components whose molecular weights were 1000 kd. In diets that were devoid of insect materials, the best results were achieved when hen egg yolk, FreAmine, yeast extract, lactalbumin, trehalose, fetal bovine serum and bovine milk were included. This is the first report of an artificial diet for in vitro rearing an eulophid parasitoid from the egg through the pupal stage.     

Laser scanning fluorescence microscopic measurement of the movement of cleaving egg surface of Rana Amurensis

By laser scanning fluorescence microscopy for quantitative measurement of fluorescence intensity changes on egg surface stained with fluorescein isothiocyanate during cleavage furrow extending forward,it was found that in area of presumptive cleavage furrow the scanning curve became ∨ shape,indicating dark stripe appeared in that place.Then the fluorescence intensity increased at the place where the bottom of ∨ shape had located,and the scanning curve turned to ∧ shape,indicating single stripe was formed.While enhanced fluorescence appeared on the borders of ∧ shape,an M shape curve was found,showing double stripe occurred.During the distance between two borders of M shape incresing from 50μm to 100μm,a fluorescence peak came to sight in the middle of the M shape,which being the cleavge furrow bottom.The two lateral sides of furrow bottom with decreasing fluorescence were nascent membrane.At that time the curve became W shape.By the sides of cleavage furrow the the stress folds became conspicous after double stripe stage,showing the stretching of the egg surface being increased.With our[31,33]and others[32] reports that polylysine could induce the appearance of nascent membrane and phytohemagglutinins could decrease or prevent the appearance of nascent membrane,we believed the idea of Schroeder[25] that increasing mechanical stress could initiate nascent membrane formation and thought that the stresslay to the outsides of cleavage furrow.     

Inhibitory effect of α-hydrazinoornithine on egg cleavage in sea urchin eggs

In fertilized sea urchin eggs which are kept in sea water containing α-hydrazinoornithine (αHO) at a concentration above 1 mM from the time of fertilization, cleavage is delayed markedly. The third cleavage is almost completely blocked by 3 mM αHO. Hydrazine, as well as ornithine, exerts no harmful effect on egg cleavage. αHO causes competitive inhibition of ornithine decarboxylase (ODC) in the egg homogenate. Polyamine levels decrease in fertilized eggs treated with αHO. The addition of ornithine (above 3 mM) to an egg culture containing αHO prevents the αHO-induced delay of cleavage. Putrescine (0.2–0.5 mM), which is the product of the reaction catalyzed by ODC, also relieves egg cleavage from the inhibited state. The same effect occurs in the presence of spermidine (0.2–0.5 mM) or spermine (0.1–0.8 mM). Especially, spermine (0.5 mM) completely cancels the inhibitory effect of αHO on egg cleavage. Egg cleavage is delayed only slightly in the presence of each polyamine (above 2 mM).     

Spectroscopic studies of D-α-tocopherol concentration-induced transformation in egg phosphatidylcholne vesicles

The effects of embedding up to 60 mol% of α-tocopherol (α-Toc) on the morphology and structure of the egg phosphatidylcholine (PC) membrane were studied using spectroscopic techniques. The resulting vesicles were subjected to turbidometric and dynamic light scattering measurements to evaluate their size distribution. The α-Toc intrinsic fluorescence and its quenching was used to estimate the tocopherol position in the membrane. Optical microscopy was used to visualize morphological changes in the vesicles during the inclusion of tocopherol into the 2 mg/ml PC membrane. The incorporation of up to 15 mol% of tocopherol molecules into PC vesicles is accompanied by a linear increase in the fluorescence intensity and the simultaneous formation of larger, multilamellar vesicles. Increasing the tocopherol concentration above 20 mol% induced structural and morphological changes leading to the disappearance of micrometer-sized vesicles and the formation of small unilamellar vesicles of size ranging from 30 to 120 nm, mixed micelles and non-lamellar structures.     

Do cuckoos choose nests of great reed warblers on the basis of host egg appearance?

Prevailing theory assumes cuckoos lay at random among host nests within a population, although it has been suggested that cuckoos could choose large nests and relatively active pairs within host populations. We tested the hypothesis that egg matching could be improved by cuckoos choosing nests in which host eggs more closely match their own, by assessing matching and monitoring nest fate in great reed warblers naturally or experimentally parasitized by eggs of European cuckoos. A positive correlation between cuckoo and host egg visual features suggests that cuckoos do not lay at random within a population, but choose nests and this improves egg matching: naturally parasitized cuckoo eggs were more similar to host eggs as perceived by humans and as measured by spectrophotometry. Our results suggest a hitherto overlooked step in cuckoo-host evolutionary arms races, and have nontrivial implications for the common experimental practice of artificially parasitizing clutches.     

Frequency distribution of egg mass of passerine and non-passerine birds based on Sch?nwetter's tables

Summary Frequency distributions of egg mass for more than 3000 species each of passerine and non-passerine birds derived from the tables ofSchönwetter are lognormal in form.

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Häufigkeitsverteilung der Eimassen nach den Angaben in den Tabellen vonSchönwetter

Zusammenfassung Die Häufigkeiten der Eimassen von jeweils über 3000 Arten der Singvögel und Nichtsingvögel aus den Tabellen im Handbuch vonSchönwetter sind lognormal verteilt (vgl. Abb.).

     

Intrinsic chiral properties of the Xenopus egg cortex: an early indicator of left-right asymmetry?

Vertebrate embryos define an anatomic plane of bilateral symmetry by establishing rudimentary anteroposterior and dorsoventral (DV) axes. A left-right (LR) axis also emerges, presaging eventual morphological asymmetries of the heart and other viscera. In the radially symmetric egg of Xenopus laevis, the earliest steps in DV axis determination are driven by microtubule-dependent localization of maternal components toward the prospective dorsal side. LR axis determination is linked in time to this DV-determining process, but the earliest steps are unclear. Significantly, no cytoskeletal polarization has been identified in early embryos capable of lateral displacement of maternal components. Cleaving Xenopus embryos and parthenogenetically activated eggs treated with 2,3-butanedione monoxime (BDM) undergo a dramatic large-scale torsion, with the cortex of the animal hemisphere shearing in an exclusively counterclockwise direction past the vegetal cortex. Long actin fibers develop in a shear zone paralleling the equator. Drug experiments indicate that the actin is not organized by microtubules, and depends on the reorganization of preexisting f-actin fibers rather than new actin polymerization. The invariant chirality of this drug response suggests a maternally inherited, microfilament-dependent organization within the egg cortex that could play an early role in LR axis determination during the first cell cycle. Consistent with this hypothesis, brief disruption of cortical actin during the first cell cycle randomizes the LR orientation of tadpole heart and gut.     

Uncommon mechanism of egg incubation in the endemic Southern hermit crab Loxopagurus loxochelis: how is this phenomenon related to egg production?

The aim of the present work was to characterize the egg production of Loxopagurus loxochelis. A total of 71 ovigerous females were obtained, 28% of which were simultaneously incubating eggs at different developmental stages. This phenomenon can be the result of incomplete fertilization, or may represent a rapid gonadal cycle by this species in this area, which is, to our understanding, the best explanation of this phenomenon. Egg volume decreased 25.6% during the incubation period. The reproductive output based on dry and wet weight was 6.8 and 19.3%, respectively. Water was the prevailing component of the eggs, representing 86.0% of the total weight at initial stage, increasing to 95.1% at the final stage. Ash content increased at the same time as a decrease in the organic content occurred, indicating the consumption of yolk and absorption of salts from the water medium. In conclusion, we hypothesized that this population has the capacity to copulate and deposit another brood even before the release of the larvae from the previous one, intensifying the reproductive effort of these hermit crabs as a strategy of adaptation in a region considered the northern limit of the geographical distribution of this species.     

Oxygen consumption in unfertilized salmonid eggs: an indicator of egg quality?

A negative correlation between oxygen consumption and fertility was observed in both steelhead and chinook salmon eggs. However, this relationship was attributed to bacterial growth. Elimination of samples with bacterial growth resulted in no significant relationship between the rate of oxygen consumption (VO2) and fertility. VO2 of unfertilized eggs of both steelhead and chinook salmon was measured over a storage period of up to 24 days (d). Despite declines in fertility during storage, VO2 did not significantly change throughout storage. The average respiration rate for steelhead eggs was 3.4 nmol O2 per egg per h, and was 4.3 nmol O2 per egg per h for chinook salmon eggs. Treatment of chinook salmon eggs with uncouplers of mitochondrial respiration, 2,4-dinitrophenol (2,4-DNP) and carbonyl cyanide 4-trifluoro-methoxyphenylhydrazone (FCCP), resulted in an increase in VO2 to 12.9 and 11.5 nmol O2 per egg per h, respectively. Treatment with the putative uncoupler, clove oil, resulted in no change in VO2, while KCN, an inhibitor of oxidative phosphorylation, reduced oxygen consumption to zero. Copper caused an increase in oxygen consumption, even in the absence of eggs, suggesting a need for caution in interpreting changes in respiration rates as a result of metal exposure. Thus, unfertilized salmonid eggs demonstrated submaximal VO2, which was not correlated with fertility.     

Induction of apoptosis in purified animal and plant nuclei by Xenopus egg extracts

We have developed a cell-free system that can trigger the nuclei purified from mouse liver and suspensioncultured carrot cells to undergo apoptosis as defined by the formation of apoptotic bodies and nucleosomal DNA fragments.The effects of different divalent cations and cycloheximide on DNA cleavage in this system were assessed.The fact that nuclei of plant cells can be induced to undergo apoptosis in a cell-free animal system suggests that animals and plants share a common signal transduction pathway triggering in the initiation stage of apoptosis.     

Differential investment in the Banggai cardinalfish: can females adjust egg size close to egg maturation to match the attractiveness of a new partner?

To test whether females can change their egg investment according to the different attractiveness (  i.e . size as measured by standard length, L _s) of a new mate after eggs have already matured in response to an earlier mate, female Banggai cardinalfish Pterapogon kauderni were first allowed to produce eggs for small (unattractive) or large (attractive) males. Then, when spawning was initiated, but prior to actual spawning, their partner was switched to either a significantly larger or a significantly smaller partner, respectively. A strong positive correlation between egg size and days until spawning with the second male was found for the females initially paired to a small and then a large male. Within a few days, these females apparently increased their egg size to match the attractiveness of their new male. No correlation between days until spawning and egg size in females initially paired to a large and then a small male, however was found, so apparently females were unable to adjust egg size in response to a decrease in mate attractiveness. Consequently, it is suggested that females can increase their egg size investment even after the onset of egg maturation and that this change can be quite rapid.     

Selection response for part period egg number and egg mass in chickens — a comparison

Summary Two sublines from each of four flocks of White Leghorn were subjected to two cycles of selection for part year egg number and part year egg mass. A family index (combined selection) was the selection criterion for each of the two traits. The generation means of an unselected pedigreed randombred control, bred and maintained along with the selected sub-lines, were used for correcting short term environmental trends. The sublines selected for a common selection criterion were considered as replicates. The control corrected generation means, when averaged over replicates, gave the mean direct and correlated responses for the selected and different unselected traits. The average genetic change per generation was 2.16 eggs in egg number selected sublines and 146 g of egg mass in egg mass selected sublines. The direct response marginally exceeded the correlated response for both part period egg number and egg mass seen in the corresponding sublines. Except for egg weight the correlated responses for different unselected traits were in the same direction in both egg number and egg mass selected sublines. While the egg weight in egg number lines did not change, its response was positive in egg mass selected lines. A comparison between the lines revealed that the egg mass selected lines matured later and laid heavier but slightly less numerous eggs than the egg number selected sub-lines.     

Modeling the cuckoo’s brood parasitic behavior in the presence of egg polymorphism

The common cuckoo Cuculus canorus is a brood parasite that utilizes many host species. These have evolved defense against parasitism to reject cuckoo eggs that look unlike their own and some cuckoos have evolved egg mimicry to counter this defense. Egg phenotype indeed plays a key role for both the cuckoo and its hosts to successfully reproduce. It has been argued that cuckoos should parasitize host nests where egg phenotype matches because this makes parasitism more successful. Details of the cuckoo’s parasitic behavior, however, largely remains unknown if they really parasitize hosts depending on “egg matching”. In this paper, we model a time sequence of parasitic events in which a cuckoo finds host nests and decides to parasitize them or not in the presence of egg polymorphism. We evaluate which strategy is optimal: (1) opportunistic parasitism where cuckoos parasitize hosts irrespective of the phenotype, or (2) non-opportunistic parasitism where cuckoos parasitize hosts where egg phenotype matches. The analysis showed that either of the two strategies can be optimal. Factors not considered in the model, e.g., ecological and evolutionary changes both in the cuckoo and the host side, are discussed to explain apparent contrasts observed in some cuckoo–host interactions.     

The serpent and the egg: unidirectional evolution of reproductive mode in vipers?

Dollo’s law, that complex characters are not regained in evolution, is a pattern applied to many systems. Recent work has evaluated unidirectional evolution in a number of contexts, and several violations of this law have been documented. These methods have also been criticized for potentially overestimating reversals. We test the hypothesis that the ancestral reproductive mode of oviparity can be regained in vipers, in opposition to Dollo’s law. We use model comparison and ancestral character state reconstruction methods that address recent criticisms, and find evidence both supporting and refuting Dollo’s predictions from different analyses. We discuss our results in the context of unidirectional evolution and review factors required for strong inference of violations of Dollo’s law.     

Does risk of egg parasitism affect choice of oviposition sites by a moth? A field and laboratory study

In many insects the eggs are highly vulnerable and egg parasitism can represent a major cause of mortality. It is thus important for the ovipositing female to find a protected site for her eggs. We have examined how egg parasitation can affect host plant choice by Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). Ovipositing moths exhibited significantly higher preference for alfalfa compared to cotton, both in the laboratory and the field. However, larval performance, in terms of development rate and the attained larval and pupal weight, was significantly better on cotton than on alfalfa. In laboratory tests no difference in larval survival on the two host plants was observed. To test the hypothesis that seeking enemy-free space could be a factor behind the preference for alfalfa, the parasitation levels on the two plants were investigated. In field tests, the egg parasitoid Chelonus inanitus (Linnaeus) (Hymenoptera: Braconidae) parasitized a significantly higher number of egg batches on cotton than on alfalfa. Furthermore, the parasitoid was significantly faster in finding and parasitizing S. littoralis eggs on cotton than on alfalfa in a cage experiment. These findings support the assumption that the preference for the inferior larval food plant, alfalfa, reflects a search for a host plant species on which attacks by natural enemies are less likely. Possible factors accounting for the preference of S. littoralis for alfalfa and the higher parasitation rates on cotton are discussed.     

Getting rid of the cuckoo Cuculus canorus egg: why do hosts delay rejection?

Egg discrimination is well documented in many hosts of avianbrood parasites, but the proximate mechanisms of egg recognitionand rejection decisions are poorly understood. Relevant in thisrespect is the observation that rejectors of parasite eggs oftendelay their response. This delay has implications for understandingmechanisms important for egg recognition and is the main focusof the present study. We investigated experimentally the relativeeffects of egg mimicry and eggshell strength of common cuckooCuculus canorus eggs on the delay in rejection in marsh warblersAcrocephalus palustris. In addition, by video recording hostresponses, we elucidate the proximate mechanisms behind thedelayed rejections. Host nests were experimentally parasitizedwith 3 types of real eggs differing in mimicry and/or eggshellstrength. Both egg mimicry and eggshell strength significantlyaffected the time to rejection, but the effect of mimicry wasdominant. The delayed rejection of mimetic eggs was explainedby the existence of latency to the release of rejection behaviorbecause of recognition problems. Second, when rejection responsetowards mimetic eggs was initiated, it was less intense comparedwith hosts experiencing nonmimetic eggs. Our results are consistentwith the hypothesis that host motivation when confronted withmimetic eggs needs to increase above a certain threshold beforerejection behavior is released, which likely minimizes the riskof recognition errors. An additional component of the delayin rejection as shown by hosts facing nonmimetic eggs was theseemingly inefficient host rejection behavior, probably reflectinglack of previous experience.