Quiescent Females Research Articles

Platelet-rich plasma and ovarian quiescence: a bovine in vitro model for regeneration of the ovary.

Ovarian quiescence can be due to hormonal deficiency usually caused by apoptosis of granulosa cells responsible for oestrogen synthesis. This study evaluated the regenerative effect of platelet rich plasma (PRP) on bovine in vitro models to understand its effect on granulosa cells. Quiescent and healthy ovarian sections were cultured in the presence/absence of PRP for 72h and, at different times (0, 24, 48 and 72h), hematoxylin-eosin and immunohistochemical detection of Ki-67 were performed. Additionally, granulosa cells collected from healthy bovine ovaries were stressed with 100ng/mL of lipopolysaccharide (LPS) in presence/absence of PRP and evaluated at 0, 4, 8 and 24h for apoptosis by acridine orange and propidium iodide staining. Enzyme-linked immunosorbent assay tests were performed to evaluate oestrogen (E2) and anti-Müllerian hormone (AMH) concentrations on cultures of ovarian slices and granulosa cells. In slides of quiescent ovaries treated with PRP, a marked and widespread positivity to Ki-67 was expressed by 40-60% of the follicular wall cells at 48h of culture. Levels of E2 and AMH were significantly higher compared to untreated quiescent samples reaching the levels of healthy control samples. PRP counteracted the LPS effect and apoptosis (at 24h, there were 93.44±3.51% live cells with LPS+PRP compared to 37±1.32% with LPS) and significantly increased concentrations of E2 and AMH. PRP can stimulate granulosa cell proliferation and counteract inflammatory processes in vitro . This treatment could improve the reproductive ability of quiescent females.

Pacific walrus (Odobenus rosmarus divergens) reproductive capacity changes in three time frames during 1975–2010

Reductions in sea ice and increases in air and seawater temperatures have been documented in the Arctic, making female Pacific walruses (Odobenus rosmarus divergens) vulnerable to changes in foraging, energy budgets, and reproductive fitness. The aim of the present study was to assess how walrus reproductive capacity has changed over a span of 35 years analyzing ovaries from three distinct time frames: 1975, 1994 to 1999 and 2008 to 2010. Ovarian weights and volumes, corpora lutea diameter, total number of corpora lutea and albicantia, and the percent of females ovulating in their current cycle were used to evaluate reproductive capacity. Ovaries were collected from walruses hunted by Alaska Native communities for subsistence purposes. There were no differences in ovarian weights or percent of quiescent females between 1975 and 2008 to 2010. Ovaries from 1994 to 1999 were significantly heavier, exhibited more corpora, and all females from this time frame were ovulating at the time of harvest. Reproductive capacity was limited during 1975, due to known density-dependent stressors; reproductive capacity increased during 1994–1999, as harvests increased and more resources became available, and in 2008–2010, females were as reproductively limited as those of 1975. The cause for this reduction in reproductive capacity is unknown, but maybe a result of multiple factors, including an increase in population size coincident with a decrease in carrying capacity, and cumulative stressors relating to sea ice loss, contaminants, and anthropogenic impacts.

Oscillations Induced by Quiescent Adult Female in a Reaction–Diffusion Model of Wild Aedes Aegypti Mosquitoes

This paper takes the reaction–diffusion approach to deal with the quiescent females phase, so as to describe the dynamics of invasion of aedes aegypti mosquitoes, which are divided into three subpopulations: eggs, pupae and female. We mainly investigate whether the time of quiescence (delay) in the females phase can induce Hopf bifurcation. By means of analyzing the eigenvalue spectrum, we show that the persistent positive equilibrium is asymptotically stable in the absence of time delay, but loses its stability via Hopf bifurcation when time delay crosses some critical value. Using normal form and center manifold theory, we investigate the stability of the bifurcating branches of periodic solutions and the direction of the Hopf bifurcation. Numerical simulations are carried out to support our theoretical results.

Response to gonadotropin-releasing hormone challenge: Seasonal variation in steroid production in a viviparous lizard, Tiliqua nigrolutea

The hypothalamic–pituitary–gonadal axis plays a central role in the regulation of gamete maturation, sex steroid production and the stimulation of reproductive behaviours in vertebrates. In seasonal breeders, the timely activation and deactivation of this control system is important to ensure successful reproduction: this process is not well understood in species which breed irregularly. Males of the viviparous blotched blue-tongued lizard, Tiliqua nigrolutea, breed annually, while females display a multiennial cycle. We investigated seasonal variation in hypothalamic–pituitary–gonadal axis responsiveness in both sexes of T. nigrolutea. We measured changes in plasma concentrations of testosterone and estrogen in response to a single intraperitoneal injection of a GnRH agonist, chicken-II LH–RH, at three reproductively distinct times of year. Plasma testosterone concentrations in males were significantly increased during gonadal quiescence, but not initial or final spermatogenesis. There was no estrogen response in males at any time of year. Conversely, in females, there was an increase in plasma testosterone, but not estrogen, concentration, in reproductively quiescent females several months in advance of a successful pregnancy. These results indicate clear variation in HPG axis activity with sex, season and reproductive condition in this seasonally breeding viviparous lizard. This study opens the way for further investigation into the mechanisms by which internal (body condition) and external seasonal cues (temperature and photoperiod) are coordinated to regulate reproduction in irregularly-breeding reptiles.

Precopulatory mate guarding influences the development of quiescent deutonymph females in the two-spotted spider mite (Acari: Tetranychidae).

Individuals of some organisms have a specific stage sensitive to environmental cues that initiate developmental plasticity which subsequently influences their entire development. Females may use male behaviour such as precopulatory mate guarding as an environmental cue to change their developmental rate. In the two-spotted spider mite Tetranychus urticae (Acari: Tetranychidae), only the first insemination results in fertilization and males guard quiescent deutonymph females. As quiescent individuals take on a silvery appearance before moulting, the period of the quiescent stage can be divided into two parts: from entering the quiescent stage to becoming silvery (1st period) and from becoming silvery to moulting (2nd period). Females may be sensitive to precopulatory mate guarding immediately before moulting (i.e. 2nd period). Thus, I examined whether precopulatory mate guarding during either period affects the total developmental duration of quiescent deutonymph females. When guarded by a male, the whole developmental duration of the quiescent deutonymph females became significantly shorter (by 3-5%) than that of solitary ones, regardless whether the guarding occurred during the 1st period, the 2nd period or both periods. In conclusion, quiescent deutonymph T. urticae females use precopulatory mate guarding by conspecific males as an environmental cue for their developmental rate, although they are sensitive to the mate guarding not only immediately before moulting.

Lethal male combats in Schizotetranychus brevisetosus (Acari: Tetranychidae) on blue Japanese oak (Quercus glauca).

Male spider mites (Acari: Tetranychidae) guard preimaginal quiescent females to reserve paternity. In a few species of Stigmaeopsis that make densely woven silky nests on the surface of host plants, mature males attack and even kill rivals to gain their rights to inseminate young females in the nest. Here we report that the adult males of Schizotetranychus brevisetosus (Acari: Tetranychidae), whose web nest construction behavior evolved independently from Stigmaeopsis spp., also exhibit highly aggressive behavior towards one another. Combat mortality was measured in an experimental design where two males in the treatment group were forced to live in a nest made by adult females on a leaf arena, while one male in the control group was allowed to live in a nest on another arena. We found that the 5-day mortality of males in the treatment group (56 and 37 % in two replicates) was significantly higher than in the control group (9 and 12 %) and that lethal combats frequently arose in the treatment group. However, we found no consistent trend for the length of the first legs, which is known to affect the outcome of battle in Tetranychus urticae and Stigmaeopsis miscanthi. This might be due to a relatively small number of measurable specimens, and the effects of body size should be explored in future studies.

Altered volatile profile associated with precopulatory mate guarding attracts spider mite males.

Proximate factors affecting animal behavior include stimuli generated by conspecifics. In spider mites of the genus Tetranychus (Acari: Tetranychidae), males guard pre-reproductive quiescent females, because only the first mating results in fertilization. In a dual-choice experiment, more adult males of T. urticae were attracted to females guarded by a male than to solitary females. Because spider mites are known to perceive volatiles, we hypothesized that guarded and solitary females differ in the volatile blends emitted. To test this hypothesis, headspace volatiles of guarded females, solitary females, and solitary males were collected, respectively. GC/MS analysis detected octanal, methyl salicylate, ethyl 4-ethoxybenzoate, and methyl cis-dihydrojasmonate in all of the groups. Orthogonal Projection to Latent Structures Discriminant Analysis (OPLS-DA) of the blends clearly discriminated guarded females from solitary females, supporting our hypothesis. Individual compounds did not show significant difference in emission rates for guarded females vs. solitary females, suggesting that differences lay in the total blend composition. OPLS-DA did not discriminate between the blends emitted by guarded females and solitary males. In conclusion, the differences in the volatile blends are likely to mediate male discrimination between guarded and solitary females.

Storage of Pentatomid Eggs in Liquid Nitrogen and Dormancy of Trissolcus basalis (Wollaston) and Telenomus podisi Ashmead (Hymenoptera: Platygastridae) Adults as a Method of Mass Production.

The eggs of pentatomid species were evaluated to parasitism by Trissolcus basalis (Wollaston) and Telenomus podisi Ashmead after storage in liquid nitrogen. Adults which emerged from stored eggs were kept at 18°C for 120 and 180days to investigate whether adult dormancy could be associated with host egg storage in liquid nitrogen as a method of mass production of these egg parasitoids. Eggs of Nezara viridula (L.) and Acrosternum pengue (Rolston) were successfully parasitized by T. basalis, as well as Piezodorus guildinii (Westwood) and Dichelops furcatus (F.) by T. podisi. The eggs of Edessa meditabunda (F.) were not parasitized by T. basalis. The emergence of T. podisi from eggs of Euschistus heros (F.) and Podisus nigrispinus (Dallas) stored for 6months was lower than the control. Females of T. basalis and T. podisi that emerged from stored eggs were kept in dormancy at 18°C. Longevity of T. basalis was influenced by the storage time and sex, but not by the interaction of sex and storage time. For T. podisi, longevity was influenced by the storage time, sex, and by the interaction of sex and storage time. For T. basalis, storage in liquid nitrogen did not affect the fecundity of quiescent females, while the number of parasitized eggs by T. podisi decreased after storage. By the joint use of these techniques, it is possible to optimize mass production of T. basalis so that its life cycle can be monitored and synchronized with the life cycle and availability of hosts.

Do males evaluate female age for precopulatory mate guarding in the two-spotted spider mite?

In the two-spotted spider mite Tetranychus urticae (Acari: Tetranychidae), because only the first mating results in fertilisation, adult males guard quiescent deutonymph females, the stage immediately before adult emergence. Previous studies showed that T. urticae males prefer to guard older rather than younger females. However, as previous experimental designs have included uncertain factors, findings have not always been sufficiently rigorous. Therefore, we reexamined whether T. urticae males discriminate between the females closest to becoming receptive and younger females. One male was introduced onto leaf squares with two differently aged quiescent deutonymph females, with time lags between the females of 3, 6, 12 or 23 h, and whether the older or younger female was guarded was recorded. When the time lags between the females were 3, 6 or 12 h, males showed no preferences. Males preferred older females over younger ones only when the time lag was 23 h. Under non-choice conditions, fewer males guarded the 23-h younger females than other older females, suggesting that the attractiveness of the younger females is weaker than older females. Our results are not fully consistent with previous studies; T. urticae males do not obviously discriminate between females closest to becoming receptive and younger females.

Brief communication: Female fecal androgens prior to the mating season reflect readiness to conceive in reproductively quiescent wild macaques

An extensive body of research exists on androgen secretion in males. Although androgens are also known to drive patterns of female reproductive physiology and behavior, little attention has been paid to these "male" hormones in females. Here, we examined female fecal androgen excretion in strictly seasonally breeding wild Assamese macaques (Macaca assamensis) and tested the hypothesis that changes in premating season fecal androgens vary with female readiness to resume ovarian cycling and thus to conceive. Across 2 years, 155 fecal samples were collected from seven reproductively quiescent (i.e., acyclic) females during the premating season months, August and September. Samples were analyzed for immunoreactive epiandrosterone (iEA), a major fecal metabolite of testosterone in macaques. Changes in iEA concentrations during the premating season were significantly negatively associated with (1) the presence of dependent offspring, i.e., lactating females showed a smaller change, and (2) with the timing of conceptions in the mating seasons, i.e., females that conceived early exhibited the greatest changes. These results provide strong evidence for a relationship between changes in androgens during the premating season and female readiness to conceive.

Indirect evidence that guarded quiescent deutonymph females invest energy to attract conspecific males in the Kanzawa spider mite (Acari: Tetranychidae)?

Because only the first mating results in fertilization in Tetranychus kanzawai (Acari: Tetranychidae), adult males guard quiescent deutonymph females (i.e., precopulatory mate guarding). A previous study reported that quiescent deutonymph females guarded by a male attract more conspecific males than solitary females and then hypothesized that guarded females release more chemical signals than solitary ones to attract males. Quiescent deutonymph females do not feed. If the hypothesis is appropriate, guarded females should invest energy in attracting males at the expense of investment in other activities, such as egg production. Therefore, we compared oviposition rates immediately after adult emergence between guarded females and solitary females. On the first day, the oviposition rate of guarded females was lower than that of solitary females. On the second day, however, there was no significant difference between female groups. These results suggest that guarded females invest energy in activities other than egg production before adult emergence and that the energetic cost is easily recoverable. We believe that our finding indirectly supports the hypothesis that guarded females release more chemical signals than solitary females to attract conspecific males.

Correlation between ovarian steroidogenesis and beta-endorphin in the Lizard Uromastyx acanthinura: Immunohistochemical approach.

In Mammals, opioid peptides are involved in various physiological processes including the reproductive function. The knowledge of the distribution of beta-endorphin, one of opioid peptides in Reptiles ovaries is very limited. Therefore, the present study used the lizard ovarian follicles to further elucidate the role of this peptide in steroidogenesis. In Uromastyx acanthinura, the localization of both this peptide and sex steroid hormone was investigated by the immunohistochemical approach. This technique was used to evaluate the distribution of these substances and their relationship. The beta-endorphin is strongly distributed in the granulosa cells and oocyte cytoplasm of the previtellogenic follicles in sexually quiescent lizards (winter) when steroidogenesis was interrupted. In spring, the signal became weak, or even absent, in the vitellogenic and previtellogenic follicles. The granulosa cells of the previtellogenic follicles showed an important synthesis of 17beta-estradiol. Females that did not undergo in vitellogenesis in spring showed the same profile than quiescent females of winter. These findings represent the first evidence of the presence of beta-endorphin in the ovary of this lizard. The seasonal variations observed in the reproductive cycle suggest that this opioid peptide is involved in the modulation of seasonal steroidogenesis.

Female mating strategy during precopulatory mate guarding in spider mites

In some taxa, females choose their mates indirectly by using male combat. In the Kanzawa spider mite, Tetranychus kanzawai, adult males guard prereproductive quiescent females. In a dual choice experiment, more males first approached females already guarded by a conspecific male than approached solitary females. In further experiments, I examined which factors attracted males during precopulatory mate guarding. Males were not attracted to males not in a mate-guarding position. In contrast, the presence of a nonbreeding individual, a juvenile male or a female in a mate-guarding position did attract conspecific males. These results suggest that the presence of any conspecific individual in a mate-guarding position stimulates quiescent females to produce chemicals that attract males. Guarded quiescent females also attracted the attention of the predatory mite, Neoseiulus womersleyi, but solitary females did not. Since N. womersleyi search for prey using chemical cues, guarded females that release more chemicals than solitary females are probably in more danger. However, males were not attracted to guarded quiescent females that had been previously exposed to N. womersleyi. Thus, quiescent females appeared to control the release of their chemicals, that is, guarded quiescent females release a male-attractant signal. When more than one male attempts to guard one female, male combat often occurs. I discuss the possibility of indirect mate choice by T. kanzawai females during precopulatory mate guarding facilitated by the use of male-attractant signals.

Effects of density experience on mate guarding behavior by adult male Kanzawa spider mites

In the Kanzawa spider mite, Tetranychus kanzawai (Acari: Tetranychidae), adult males guard pre-reproductive quiescent females. I experimentally examined the effects of density experience during development and/or after adult emergence on precopulatory mate guarding behavior by T. kanzawai males. Mate guarding behavior was modified by density experience after adult emergence. When males had previously experienced high density after adult emergence (n = 71), 73.2% of them engaged in precopulatory mate guarding. In contrast, when males had previously experienced low density after adult emergence (n = 82), 61.0% of them did not guard females. Mate guarding with physical contact occurred more frequently when males had previously experienced a high density of potential rivals than when they had not, but the difference in behavior between the two groups of males was marginally not significant. Nevertheless, these results suggest overall that T. kanzawai males change mate guarding behavior in response to previously experienced density.

Effects of predation risk on mating behavior of the Kanzawa spider mite

In the Kanzawa spider mite, Tetranychus kanzawai, adult males locate pre-reproductive quiescent females and engage in precopulatory mate guarding. We found that re-reproductive quiescent females preferred to be near veins, rather than other leaf parts, and moreover, adult males spent more time along the vein than on other parts. Consequently, T. kanzawai males found more quiescent females along veins than those on other parts. However, the predatory mite Neoseiulus womersleyi also found more quiescent T. kanzawai females along veins than those on other parts. Moreover, N. womersleyi found more guarding males than solitary males of T. kanzawai. Thus, we experimentally examined the effects of predation risk on the mating behavior of T. kanzawai. The presence of N. womersleyi reduced T. kanzawai female preference for vein vicinity as a quiescent site. Although the predation risk of guarding T. kanzawai males was lower than that of solitary males after detection by predators, the presence of N. womersleyi also reduced the proportion of guarding T. kanzawai males. These results suggest that the possible benefits of preferring vein vicinity as quiescent sites by T. kanzawai females is outweighed by predation risk in the presence of predators, and that the risk of detection by predators would be more important for T. kanzawai males than the risk of being preyed upon.

Does adrenal responsiveness vary with sex and reproductive status in Egernia whitii, a viviparous skink?

In mammals, oestrogens generally stimulate adrenal function whilst androgens are inhibitory, and gestating females down-regulate their acute response to stressors in order to protect current reproductive investment. This study aimed to determine if adrenocortical function is similarly modulated by sex and reproductive status in the viviparous lizard, Egernia whitii. We compared the adrenocortical response to acute capture stress in female E. whitii during active (post-ovulatory and gestating) and quiescent (post-partum) phases of their reproductive cycle. We also compared the responses of reproductively quiescent males and females to acute stress and ACTH challenge to determine if there are sex-related differences in HPA axis activity when the influence of reproductive hormones is minimal. The females’ responses to acute capture stress varied significantly with reproductive stage, and quiescent females displayed the strongest immediate response, with a rapid and sustained increase in plasma corticosterone (CORT) concentrations. Post-ovulatory females showed the most conservative adrenocortical response and while gestating females showed a large immediate response, this was not as prolonged as in quiescent females. Reproductively quiescent males and females exhibited similar responses to acute stress, and also responded similarly to ACTH injection, with plasma CORT reaching maximal concentrations of 52.1 and 59.4 ng/mL, respectively. Reproductively quiescent females treated with oestrogen exhibited greater responsiveness to ACTH than control females, although basal plasma CORT concentrations were unaltered: these results suggest that the attenuation of the acute stress response observed in reproductively active females of E. whitii may be regulated upstream of ACTH secretion. Our results demonstrate that the activity of the HPA axis is modulated by reproductive status in this viviparous reptile, and that gestating females are able to buffer their embryos from the potentially adverse effects of elevated plasma corticosteroids.

Microhabitat choice and diet of rodents in Maynugus irrigation field, northern Ethiopia

AbstractAn ecological study on the choice of microhabitat and diet of small mammals was carried out in Maynugus irrigation field of the Tigray region in northern Ethiopia. Abundance of rodents was high during the reproductive phase of the agricultural plants. Mastomys erythroleucus occurred more frequently in vegetable fields, whereas Arvicanthis dembeensis was more frequent in habitats with monocot plants. Scrotal males and reproductive females consumed more food by weight than abdominal males and quiescent females. Arvicanthis dembeensis consumed more food than M. erythroleucus. Both the species consumed more food during the main rainy season. All the cultivated plants were attacked by these rodents with a degree of difference in relation to season, species, sex, age and sexual condition. As rodent attack was more intense during the fruiting phase of the plants, rodent control management should be carried out during the flowering phase.

The effect of male size and operational sex ratio on male mating success in the common spider mite, Tetranychus urticae Koch (Acari: Tetranychidae)

Abstract. The effect of male size and operational sex ratio (number of adult males/number of adult males + number of females available for mating) on male mating success in the spider mite was studied both in the field and in the laboratory. Larger males defended females less intensely and for shorter periods, but had a higher probability of mating with a previously guarded female than smaller males. With increasing operational sex ratio agonistic interactions between males occurred more frequently and lasted longer. Large males guarded more selectively, i.e. spent less time guarding, than small ones. With increasing density of quiescent females (females in the final juvenile stage) all mates became more selective. Only small males guarded less selectively with increasing male bias. Females mated repeatedly. A female's first mating lasted longer on average than subsequent matings. In the absence of male-male competition, absolute mate size was positively correlated with the duration of the first mating. When males competed for females, the larger males were better able to resist attempted interference in mating than smaller males. Compared with balanced or female-biased operational sex ratios, mating interferences tended to be more common, although not significantly so, when the operational sex ratio was biased towards males. A male's chance to mate twice with a given female decreased with increasing operational sex ratio. Depending on the degree of male-male competition in a spider mite colony, the effects of male size on fighting ability, chance to mate, duration of precopulatory mate guarding and duration of mating will contribute to variation in male reproductive success in natural populations.

Guarding Behavior and Reproductive Isolation in Two Tetranychid Mite Species (Acari: Tetranychidae)

Female deutonymphs (the last immature instar) of the twospotted spider mite, Tetranychus urticae Koch, and the Banks grass mite, Oligonychus pratensis (Banks), become quiescent before emerging as adults. Adult males guard these quiescent females and mate with them as soon as they emerge. Interspecific guarding was common in no-choice tests: 52.2% of T. urticae males guarded quiescent O. pratensis female deutonymphs and 31.0% of O. pratensis males guarded T. urticae females. However, when offered a choice between con- and heterospecific females, 87.7% of T. urticae males and all O. pratensis males guarded conspecific females. This tendency to guard conspecific females may act as a premating isolating mechanism by reducing the incidence of heterospecific matings. In no-choice tests, the arrestment responses of males of both species to pheromone extracted from con- and heterospecific female quiescent deutonymphs were not significantly different. Similarly, in choice tests, males showed no preference for conspecific pheromone over pheromone extracted from heterospecific females. Arrestment pheromones do not appear to facilitate reproductive isolation in these species.

Bionomics of Nodele calamondin Muma (Acarina: Cheyletidae) fed on Lepidoglyphus destructor (Schrank) (Acarina: Glycyphagidae) at two constant temperatures

Nodele calamondin Muma is a predator of other mite species and of small insect larvae. Unmated females produced only male offspring (arrhenotoky), which subsequently mated with their mothers to produce female as well as male offspring. At 29.5 °C these females became adults an average of 47.3 days after the emergence of the mother. Males have one nymphal stage in their development and females have two nymphal stages. Males guarded the quiescent deutonymph females and mating took place as soon as the females emerged as adults. Unmated females lived more than twice as long as mated females and laid about 89% of the number of eggs laid by their mated sisters. The average duration of a generation was 62 days at 25 °C and 34 days at 29.5 °C. Net reproductive rate (ratio of female births in two successive generations) was 20 at 25 °C and 34 at 29.5 °C.