Egg Resorption Research Articles

Effect of egg production dynamics on the functional response of two parasitoids.

Functional response describes the number of hosts attacked by a parasitoid in relation to host densities and plays an important role by connecting behavioral-level processes with community-level processes. Most functional response studies were carried out using simple experimental designs where the insects were confined to a plain and small arena with different host densities during a fixed period of time. With these designs, other factors that might affect the functional response of parasitoids were not analyzed, such as fecundity, age, and experience. We proposed a series of latent-variables Markovian models that comprised an integrated approach of functional response and egg production models to estimate the realized lifetime reproductive success of parasitoids. As a case study, we used the parasitoids Anagyrus cachamai and A. lapachosus (Hymenoptera: Encyrtidae), two candidate agents for neoclassical biocontrol of the Puerto Rican cactus pest mealybug, Hypogeococcus sp. (Hemiptera: Pseudococcidae). The tested species were assessed according to their physiology and prior experience. We estimated the number of mature eggs after emergence, egg production on the first day, egg production rate, the proportion of eggs resorbed, egg resorption threshold, and egg storage capacity. Anagyrus cachamai and A. lapachosus both presented a type III functional response. However, the two parasitoids behaved differently; for A. cachamai, the number of parasitized hosts decreased with female age and depended on the number of mature eggs that were available for oviposition, whereas A. lapachosus host parasitism increased with female age and was modulated by its daily egg load and previous experience. The methodology presented may have large applicability in pest control, invasive species management, and conservation biology, as it has the potential to increase our understanding of the reproductive biology of a wide variety of species, ultimately leading to improved management strategies.

Reproductive consequences of thermal stress-induced bleaching in the giant clam Tridacna crocea

Reproduction is a fundamental process necessary for maintaining a population. However, reproductive processes are sensitive to thermal stress which can cause bleaching in reef organisms such as corals and giant clams. Here we examined the phototrophic and physiological performances, particularly the reproductive processes, in Tridacna crocea during bleaching and recovery periods. Giant clam individuals were induced to bleach at heated treatment (32-33 °C) for 16 days and allowed to recover at 28-29 °C for 35 days. The control giant clams were kept at 28-29 °C. Heated giant clams showed lower phototrophic performances (Fv/Fm and photosynthesis), but their respiration and survival were similar to control giant clams. The gonadosomatic index (GSI) was lower, and the proportion of regressive eggs (i.e., eggs that are no longer viable) was higher in heated than in control giant clams. However, heated giant clams were able to maintain their egg size. In addition, T. crocea showed recovery of phototrophic potential and color of mantle but not of their reproductive output after a month of recovery. Our results indicate that bleaching reduces the reproductive output in giant clams by disrupting their gametogenesis, such as through egg resorption, but giant clams showed potential reproductive strategy, through maintenance of their egg size, to ensure the quality of their offspring. Furthermore, one month of recovery is not sufficient to restore the normal reproductive processes in T. crocea, which may delay their population recovery after a bleaching disturbance.

Tartrazine exposure results in histological damage, oxidative stress, immune disorders and gut microbiota dysbiosis in juvenile crucian carp (Carassius carassius).

Tartrazine (TZ) is an azo dye widely used in foods, cosmetics, beverages, textile, and leather. In recent years, there are reports on detecting azo dyes in the aquatic environment, so the impact of these compounds on aquatic organisms could not be ignored. In this study, we aimed to evaluate the adverse effects of TZ exposure on teleosts' embryo development and juvenile's health by using crucian carp (Carassius carassius) as the experimental fish. The results showed that embryos exposed to TZ (0.19, 0.76 and 1.5mM) exhibited a deformity, delayed egg resorption and decreased fertilization and hatching rate. When the juvenile fish were exposed to TZ at a level higher than those present in water for 30 days caused severe histopathological damages of the gill, intestine, kidney and liver. Antioxidant enzymes (CAT, SOD and GSH-Px) activities in the gill, intestine and liver, exhibited a decreasing trend after TZ exposure, while MDA contents elevated. TZ exposure also resulted in the upregulation of pro-inflammatory cytokines (il1 and il6), lysozymes (lyz), complement component 3 (c3), and β-defensin 3 (defb3). In addition, TZ exposure also affected the intestinal microbiota structure. In summary, the data in the present study indicated that TZ exposure reduce the embryo fertilization and hatching rate; cause histopathological damage of tissues, trigger oxidative stress, innate immune disorders and dysbiosis of gut microbiota in juvenile crucian carp. Therefore, it is necessary to be informed about the hazards of TZ exposure and the discharge of the dye into waters should be strictly administrated to prevent environmental pollution.

Intraspecific variability in egg maturation patterns and associated life-history trade-offs in a polyembryonic parasitoid wasp

1. Life-history theory predicts a trade-off between the resources allocated to reproduction and those allocated to survival. Early maturation of eggs (pro-ovigeny) is correlated with small body size and low adult longevity in interspecific comparisons among parasitoids, demonstrating this trade-off. The handful of studies that have tested for similar correlations within species produced conflicting results. 2. Egg maturation patterns and related life-history traits were studied in the polyembryonic parasitoid wasp, Copidosoma koehleri (Hymenoptera: Encyrtidae). Although the genus Copidosoma was previously reported to be fully pro-ovigenic, mean egg loads of host-deprived females almost doubled within their first 6 days of adulthood. 3. The initial egg-loads of newly emerged females were determined and age-specific realised fecundity curves were constructed for their clone-mate twins. The females' initial egg loads increased with body size, but neither body size nor initial egg load was correlated with longevity and fecundity. 4. The variation in initial egg loads was lowest among clone-mates, intermediate among non-clone sisters and highest among non-sister females. The within-clone variability indicates environmental influences on egg maturation, while the between-clone variation may be genetically based. 5. Ovaries of host-deprived females contained fewer eggs at death (at ∼29 days) than on day 6. Their egg loads at death were negatively correlated with life span, consistent with reduced egg production and/or egg resorption. Host deprivation prolonged the wasps' life span, suggesting a survival cost to egg maturation and oviposition. 6. It is concluded that adult fecundity and longevity were not traded off with pre-adult egg maturation.

Suitability assessment of three Trichogramma species in the control of Mythimna separata (Lepidoptera: Noctuidae)

AbstractMythimna separata (Walker) is a serious cosmopolitan pest. Trichogramma species have been used worldwide as biological control agents of lepidopteran pests. However, no data on the control efficiency of Trichogramma species on this pest have been reported. We evaluated the suitability of M. separata eggs for three Trichogramma species, Trichogramma dendrolimi Matsumura, T. ostriniae Pang et Chen and T. japonicum Ashmead, and compared the suitability with that of Corcyra cephalonica (Stainton) eggs. The parasitism rate, development time, emergence rate, female proportion, body size and egg load of female offspring indicated that the M. separata egg is a suitable host for the three Trichogramma species. On the other hand, the non‐emergence rate and the relationship between egg load and body size reflected that M. separata eggs are less suitable for the three Trichogramma species than C. cephalonica eggs. Egg resorption occurred in T. japonicum 4 days after emergence.

Comparing parasitoid life histories

AbstractSpecies and clades are characterized by their unique combinations, or suites, of life‐history traits. In parasitoids, traits include a core group common to other organisms, and a parasitoid‐specific group. These organize into several sets of mutually covarying traits which overlap a little, but not wholly, with other sets. Across parasitoid species, host size, clutch size, and body size tend to covary. Roughly independent of these is a dichotomy between idiobionts (host does not develop after parasitization), which tend to have fast development but slow adult life histories, and koinobionts (hosts develop after parasitization) with the opposite set of traits. Consistent links between the dichotomy and host characteristics remain elusive. A low ovigeny index (low allocation to early reproduction) is found in idiobionts, and is a predictor of some of the dichotomous set, but also more host feeding, egg resorption, solitary development, and larger bodies. Variation in fecundity, in taxonomically restricted studies, is predicted by the host stage attacked, but this is not reflected in taxonomically broad studies. The reasons behind trait co‐variation are only partly understood. Analyses of evolutionary lability suggest that variation in development mode and body size tends to be clustered within higher taxonomic levels, with variation in other traits such as lifespan, fecundity, and egg size more evenly distributed across taxonomic levels. Thus, taxonomically constrained radiations of parasitoids tend to retain a particular suite of traits that revolve around fundamental shifts in hosts and their use that occur relatively rarely. Parasitoids illustrate how the fast‐slow continuum can be much less extensive than in mammals, how the ecology of the host affects the life histories of parasitic organisms, how different taxa require different life‐history theories, and how understanding resource allocation in early adult life can help explain life‐history variation.

Ontogeny and reproductive biology of Diadegma semiclausum (Hym.: Ichneumonidae), a larval endoparasitoid of Diamondback Moth, Plutella xylostella (Lep.: Plutellidae)

In this article, the ontogeny and reproductive biology of Diadegma semiclausum (Hym.: Ichneumonidae), an important parasitoid of Plutella xylostella (Lep.: Plutellidae) are described in detail. We did dissect parasitized P. xylostella larvae in phosphate-buffered saline and determine the external morphology of its parasitoid at all developmental stages. The developmental duration of its immature stages, adult longevity, total oviposition period and fecundity of the parasitoid are determined at 24 ± 1 °C, 65 ± 5% R.H., and a photoperiod of 16:8 h L:D. The mean duration of egg and larval stages is 9.56 days and the prepupa and pupa stages last for 8.27 days. In average, female longevity is 1.31 times longer than that of males, and females lay 300 eggs in total. The peak of D. semiclausum oviposition is on the eighth day after mating. The egg loading pattern of D. semiclausum was investigated to determine the parasitoid ‘ovigeny index’ throughout the female's parasitoid lifetime. Initial egg load in immature females (<2 h age) is 1.45 per female and the mean lifetime potential fecundity (total immature and mature oocytes), at four interval ages, is 34. With an ovigeny index value of 0.038, D. semiclausum is considered moderately to strongly synovigenic. In the absence of the host, after 3 days, the number of eggs is decreased in D. semiclausum. Our results demonstrated that there is a negative relation between the ovigeny index and egg resorption in this parasitoid.

Pattern of Egg Maturation and Oviposition forMicroplitis rufiventris(Hymenoptera: Braconidae) Wasps Given Different Schedules of Host Availability and Food Resources

AbstractThe effects of the oviposition regime on egg maturation rate in the synovigenic parasitoid, Microplitis rufiventris Kokujev were investigated. In non-ovipositing wasps, females normally reach a peak of egg maturation rate on 1 d posteclosion. Egg maturation slowed down once the maximum oviduct egg load was reached on 2 d posteclosion. In wasps manipulated for 20 ovipositions per day, the egg maturation rate during the first 3 d posteclosion was lower compared with those manipulated for 40 ovipositions per day. The rate of egg maturation in 1-d-old wasps was found to be the highest for those that experienced 60 ovipositions per day. The maturation rate in females offered unlimited hosts was not significantly greater than those manipulated for 40 ovipositions per day. The act of oviposition significantly increased the rate of egg maturation and minimized egg resorption in the female wasp. The distribution of mature eggs in the ovaries at death is apparently associated with the oviposition regime. Trade-offs between egg maturation rate and female longevity were quite evident.

Effect of Holding Diet on Egg Formation ofTamarixia radiata(Hymenoptera: Eulophidae), Parasitoid ofDiaphorina citri(Hemiptera: Psylloidae)

Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae), is an arrhenotokous ectoparasitoid of Diaphorina citri Kuwayama (Hemiptera: Psylloidae), vector of huanglongbing (HLB) or citrus greening disease. Mass-rearing parasitoids for augmentative biological control has created the need to find storage conditions that will optimize egg load upon release. Food provided to females during the holding period may be foremost among factors that determine the number of eggs available for oviposition following storage. Pairs of newly emerged T. radiata were provided with 8 different diet treatments: water, honey, Nu-Lure® (a proteinaceous liquid made from 44% hydrolyzed corn gluten meal), host nymphs, honey Nu-Lure, honey host nymphs, Nu-Lure host nymphs, and honey Nu-Lure host nymphs. Female wasps were dissected after 5, 10, 15, and 20 days and mature eggs counted. An average of 4.6 eggs was observed in ovaries of newly emerged females. Honey alone was sufficient for female survival, but egg resorption took place within 5 days after emergence. The combination of honey Nu-Lure resulted in female survivorship similar to a diet of host nymphs, but egg formation was less than with nymphs provided. Tamarixia radiata formed more eggs feeding on mixed diets (Nu-Lure honey nymphs or Nu-Lure nymphs) compared to nymphs alone. However no artificial diet substituted for nymphal hemolymph.

Egg maturation dynamics of the parasitoid Microplitis rufiventris: starvation speeds maturation in early life

The number of mature eggs carried by a female parasitoid at any given moment (egg load) is a fitness‐related parameter affecting reproductive potential and impacting upon host population dynamics. Microplitis rufiventris Kokujev (Hymenoptera: Braconidae) is a solitary koinobiont endoparasitoid wasp of several noctuid pests, including Spodoptera littoralis. The number of mature eggs carried by females at emergence is approximately 50. The rate of egg maturation is strongly affected both by feeding status and access to host larvae. In early adult life, egg maturation rates are lower for 6–72 h in fed wasps compared with food‐deprived wasps. When given access to hosts, honey‐fed wasps live for approximately 9 days with high lifetime fecundity (226 eggs). By contrast to early adult life, the total realized fecundity is positively affected by feeding status, where water‐fed and starved females have 140 and 107 eggs, respectively. Egg resorption is most pronounced in the later life of females. The results suggest, in addition to confirming the effect of honey‐feeding on total fecundity, that fecundity of starved wasps includes rapid egg maturation early in life, which potentially could improve the performance of the parasitoid as a biological control agent.

Is parasitoid acceptance of different host species dynamic?

Summary Parasitoid acceptance of host individuals that differ in suitability is dynamic, varying with physiological state and experience. Female parasitoids with high egg loads and low life expectancy (i.e. time limited) are more willing to accept hosts with low suitability for progeny development than females with low egg loads and high life expectancy (i.e. egg limited). However, studies of dynamic acceptance behaviour in parasitoids have only considered high‐ vs. low‐suitability host individuals within the same host species. Here, we report the first results on whether acceptance of individuals from different host species that vary in suitability is also dynamic, using two aphid parasitoid species in the genus Aphelinus (Hymenoptera: Aphelinidae). Stressors (starvation and age) and experience that increase time limitation did not affect the acceptance of low‐suitability host species by two Aphelinus species with reciprocal specificities. Oviposition in a high‐suitability host species increased with egg load, but did not vary with egg load for females exposed to low‐suitability host species. This is an unexpected pattern since it results in proportionally higher acceptance of low‐suitability hosts with decreasing egg load. The stability of behavioural host specificity in these parasitoids under very stressful conditions might be explained by (i) frequent transient egg limitation, (ii) higher fitness from egg resorption than oviposition or (iii) neural constraints on host recognition. If neural constraints restrict the ability of these specialists to change their behaviour under stress, we predict that generalist species of Aphelinus should show greater dynamism in acceptance of low‐suitability hosts. We are testing this prediction using Aphelinus species with very broad host ranges.

A quantitative framework for ovarian dynamics

Summary Ovarian dynamics describe the highly complex interplay between egg maturation, oviposition, egg resorption and the factors affecting them. While these processes have been intensively studied, further progress has been impeded by the lack of generally applicable quantitative tools to analyse experimental data. The purpose of this study is to provide a quantitative framework based on a state space describing the different levels of egg maturation and resorption states (non‐mature, mature, resorbing and resorbed eggs). This quantitative framework enables both the transition rates between the observable states and the unobservable states, such as resorbed eggs, to be estimated rigorously. We applied this approach to the ovarian response of the parasitoid species Nasonia vitripennis during a period of host and food deprivation. A simple system of exclusively linear differential equations with four states captures the salient properties of the data. Resorption is shown to occur concurrently with egg maturation. We highlight widespread confusion associated with the use of the generic term ‘rate of egg resorption’ that has been used to describe three fundamentally different physiological processes that have contrasting rates. The approach is also applied to an older data set gathered by Edwards (The Quarterly Journal of Microscopical Science, 1954, 95, 459–468), which encompasses a wider range of manipulations on host and food availabilities, as well as data on oviposition. Our analysis shows that ovaries only function at full capacity after a first host meal and hints towards anautogeny in this species. While this study primarily focuses on insects, the methodology is general and is suitable for studying the reproductive biology of a broad class of organisms, including plants.

Coping with an unpredictable and stressful environment: The life history and metabolic response to variable food and host availability in a polyphagous tephritid fly

The way energy resources are used under variable environmental conditions lies at the heart of our understanding of resource management and opportunism in many organisms. Here we sought to determine how a time-limited, synovigenic and polyphagous insect with a high reproductive-potential ( Anastrepha ludens), copes behaviourally and metabolically with environmental unpredictability represented by constant and variable regimes of host availability and variation in food quality. We hypothesized that an adaptive response to a windfall of nutritious food would be the rapid accumulation of energy metabolites (whole body lipids, glycogen and proteins) in the female. We also studied patterns of oogenesis as an indicator of egg-reabsorption under stressful environmental conditions. As predicted, patterns of energy metabolites were mainly driven by the quality and temporal pattern of food availability. In contrast, patterns of host availability had a lower impact upon metabolites. When given constant access to high quality nutrients, after an initial increase early in life, whole body lipids and glycogen were regulated downward to a steady-state level and somatic protein levels did not vary. In contrast, when food uncertainty was introduced, whole body lipid, glycogen and protein oscillated sharply with peaks associated with pulses of high-quality food. Production of eggs was highest when offered continuous access to hosts and high quality food. Importantly, females fully recovered their reproductive capacity when fruit became available following a period of host deprivation. With no evidence of egg resorption and high levels of egg dumping, it appears that egg dumping may favour the continuous production of eggs such that the female’s reproductive tissues are ready to respond to rapid changes in the availability of hosts. Our results exemplify the capacity of insects to maximize reproduction under variable and stressful environmental conditions.

Does Host Size and Feeding Status Influence the Egg Load of Microplitis rufiventris (Hymenoptera: Braconidae)?

Abstract Laboratory experiments were conducted to determine the effect of host instar and feeding status on the egg load of early life stage in Microplitis rufiventris Kokujev (Hymenoptera: Braconidae), a solitary koinobiont endoparasitoid of some noctuid pests. The wasps that developed from fourth or fifth instars of Spodoptera littoralis (Boisduval) larvae were heavier in weight than those from earlier stages. Different numbers of mature eggs were found in the two ovaries of the female wasp. Egg loads, corresponding to fitness, were significantly influenced by female weight and feeding status. However, the interactions between the two treatment factors were not significant. The average number of mature eggs carried by females at eclosion time ranged from 52 eggs in smaller wasps to 62 eggs in larger wasps. Females that were fed had higher egg loads and egg maturation rate than unfed females. However, female wasps were capable of maturing considerable number of eggs without feeding; suggesting that they produce a certain portion of eggs from nutritional reserves that had been stored during larval stage. Female wasps are weakly synovigenic, with an egg maturation at a rate of ≈1.8 eggs per h. Further investigation is required to verify the rate of egg maturation and eventually egg resorption in different stages of adult female M. rufiventris.

Longevity and fecundity ofEulophus pennicornis, an ectoparasitoid of the tomato mothLacanobia oleracea,is affected by nutritional state and diet quality

1 Adult female Eulophus pennicornis require a source of nutrition, provided by sources such as pollen, nectar and honeydew or by host feeding, to promote longevity and facilitate egg production. There is potential for parasitoids to be exposed directly to contaminants, including gene products in transgenic crops, through feeding on plant materials, honeydew or hosts. Among such potential contaminants are lectins such as Galanthus nivalis agglutinin (GNA) and concanavalin agglutinin (Con A). 2 The effect of direct exposure to honey diets containing GNA and Con A on the longevity and fecundity of E. pennicornis was examined. These lectins have been expressed in a number of plant species for the control for various insect pests. Both GNA and Con A significantly reduced longevity and fecundity at the highest concentration used (0.5% w/v). The effect on fecundity was shown to be related to a reduction in longevity. 3 Examination of the gustatory response of adult female E. pennicornis to honey diet containing 1% w/v GNA or Con A revealed no significant differences in consumption rate on first exposure. A significant reduction in the time spent feeding on diet containing 1% Con A was found on the second exposure to the diet. This could have been the result of either a conditioned aversion response or the intoxication of the insect. The effect of Con A on longevity and fecundity could have been, in part, a result of reduced food intake. 4 Studies on nutrition and egg resorption demonstrated that the availability of honey solution prolongs the longevity of E. pennicornis and the lack of a source of nutrition promotes oosorption. 5 A greater understanding of feeding behaviour and ovigeny is required to understand fully the potential ecological consequence of transgenic crops on parasitoid species through routes of direct exposure to transgene products.

Stochasticity and controllability of nutrient sources in foraging: host‐feeding and egg resorption in parasitoids

The trade‐off between current and future reproduction has led many organisms experiencing stochastic reproductive opportunities to be flexible in their resource acquisition and allocation rules. Many parasitoid wasps display flexibility in choosing to host‐feed or oviposit on a host and possess an ovarian system enabling nutrient reallocation through egg resorption.The aim of this work is to assess the complementary adaptive values of host‐feeding and egg resorption as functions of host density in a synovigenic (maturing eggs throughout its adult life) parasitoid,Eupelmus vuilleti(Hymenoptera: Eupelmidae), for which there is a uniquely large base of relevant knowledge. We developed a series of models of increasing complexity, starting from a simple analytical model without egg resorption and moving on to data‐rich stochastic dynamic programming models (SDP), without and with resorption.The analytical model enabled the characterization of two, long‐ and short‐term, foraging strategies which determine host usage. Oviposition is favored at low host densities (leading to the short‐term strategy), while host‐feeding is favored at high host densities (leading to the long‐term strategy). The change of strategy occurs abruptly at intermediate host densities. The SPD models not only confirmed these predictions, but also identified smaller regions of decisions driven by day/night cycles and approaching death and predicted major shifts in daily activity patterns according to the chosen strategy. The fitness gain due to resorption is highest at intermediate host densities, where females adopt the riskier but more profitable long‐term strategy. Such a result contrasts with the generally held view, which assumes highest gains at the lowest host densities. A counterintuitive result is the higher prevalence of host‐feeding associated with the ability to resorb eggs.Considering egg resorption as a last‐resort strategy is underestimating its adaptive value, which is best understood with reference to other sources of nutrients. Its deterministic and controllable nature acts as insurance to forage and oviposit at low host densities, despite irregular food availability and potential death through starvation. Thus timing, not so much overall energy gain, matters in egg resorption. The approach can be extended to other situations, and we highlight an unexpected analogy of our results with the hoarding behavior of vertebrates.

Reproduction in a variable environment: How does Eupelmus vuilleti, a parasitoid wasp, adjust oogenesis to host availability?

Oogenesis of the parasitoid wasp Eupelmus vuilleti is known to be dependent on host availability. However, examination of ovarian dynamics by microscopy showed that oogenesis and vitellogenesis are initiated before female eclosion and proceed 1–2 days after, independent of host presence. Oogenesis continued beyond the 2nd day only in the presence of hosts, otherwise it was replaced by egg resorption. It is thus possible to distinguish between host-independent and host-dependent periods of oogenesis. In the presence of host, each ovariole (three per ovary) contained generally three oocytes: a fully mature oocyte, a nearly mature one and an immature one. However, host deprived-females resorbed their most mature and their smallest oocytes, but kept one almost mature oocyte per ovariole. Comparison of zero, short and long host deprivation periods showed that females always had the ability to quickly lay eggs to exploit any new host. However, increased deprivation led to a reduction in the number and the viability of eggs. Enzymo-immunological measurements of ecdysteroids were made in whole females, in dissected ovaries and in newly laid eggs. Our results indicated that ecdysteroids play a major role as circulating hormones involved in the regulation of oogenesis.

Egg resorption behaviour by the solitary egg parasitoid Anaphes nitens under natural conditions

AbstractWe investigated under outdoor conditions and inside a climate chamber: (i) whether Anaphes nitens Girault (Hymenoptera: Mymaridae), an egg parasitoid of the Eucalyptus snout beetle, Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae), experienced egg resorption, and (ii) how various treatments (location, food, and/or host supply) and body size influenced egg load, egg resorption, fecundity, and longevity. One‐day‐old females were mated and randomly assigned to five groups: (A) honey + hosts, (B) water + hosts, (C) only honey, (D) only water, and (E) control females killed at emergence. We compared the egg load of the newly emerged females, which represent the control group (egg load = ovarian eggs present at emergence), with the lifetime egg load (i.e., ovarian eggs + emerged offspring + not emerged offspring) of the females with various host and diet treatments, by dissection of the ovaries to find evidence of egg resorption. All groups reared outdoors had fewer eggs than the control, while indoors there was no significant difference. Outdoors, starved but host‐provided wasps (B) experienced the highest reduction of the lifetime egg load (51%). Groups without access to food (B + D) resorbed more eggs than groups provided with honey (A + C). Females with honey and hosts (A) had the highest lifetime fecundity, but those with water and hosts (B) showed a higher daily realized fecundity. Host‐deprived females with access to food (C) attained the longest lifespan. Our results suggest that under stress conditions, such as low temperature and food shortage, A. nitens females practice egg resorption, probably to save energy.

The state of the reproductive system in Caspian inconnu Stenodus leucichthys (Salmoniformes, Coregonidae) with the sexual cycle completed under conditions of fish hatchery

The anthropogenic effect on the ecosystem of the Volga and the Caspian Sea and absence of the necessary conditions for keeping the Caspian inconnu Stenodus leucichthys at the fish hatchery have a negative influence on the state of the fish reproductive system. As a result only few females matured normally, and a number of individuals with various degrees of egg resorption made up 18% in 2005. Using hormonal stimulation made it possible to achieve maturity of practically all females and to obtain the mature sex cells of high fish cultural quality. No significant differences in the reproductive systems of the spawners procured in the winter and spring spawning migration were revealed. The injuries and diseases of females have a negative influence on the fish cultural characteristics (specific working fertility, egg fertilization, and embryonic development). The completion of gonad maturation and spermiation in 97% of males occurred spontaneously when the temperature decreased, and 88% of individuals had a high fertility.

Phenotypic plasticity of the reproductive system of female Leptinotarsa undecimlineata

AbstractThe effect of a non‐host plant, Solanum myriacanthum, on ovarian dynamics and longevity of Leptinotarsa undecimlineata (Stål) (Coleoptera: Chrysomelidae) was studied under laboratory conditions. Females reared on the natural host, S. lanceolatum, served as controls. Female beetles did not accumulate eggs on the non‐host. After continuous exposure to S. myriacanthum, the production of basal oocytes was diminished and oocytes were reabsorbed. Oocyte size, however, was not affected when compared to females fed with S. lanceolatum. In control females, the first mature eggs appeared at 34 days old. No eggs matured in females fed with the non‐host in the 54‐day duration of our experiment. Continuous exposure to the non‐host resulted in significantly less resorption of reproductive resources than a stress period of 20 days on the non‐host. Egg resorption was completely reversible after the preferred host was re‐offered for another 20 days. Further studies under field conditions will be necessary to understand why this Leptinotarsa species uses only one of two sympatric Solanum species.