Virgin Females Research Articles

Assessment of Genotoxicity of Zinc Oxide Nanoparticles Using Mosquito as Test Model.

The widespread applications of ZnO NPs in the different areas of science, technology, medicine, agriculture, and commercial products have led to increased chances of their release into the environment. This created a growing public concern about the toxicological and environmental effects of the nanoparticles. The impact of these NPs on the genetic materials of living organisms is documented in some cultured cells and plants, but there are only a few studies regarding this aspect in animals. In view of this, the present work regarding the assessment of the genotoxicity of zinc oxide nanoparticles using the mosquito Culex quinquefaciatus has been taken up. Statistically significant chromosomal aberrations over the control are recorded after the exposure of the fourth instar larvae to a dose of less than LD20 for 24 h. In order to select this dose, LD20 of ZnO NPs for the mosquito is determined by Probit analysis. Lacto-aceto-orcein stained chromosomal preparations are made from gonads of adult treated and control mosquitoes. Both structural aberrations, such as chromosomal breaks, fragments, translocations, and terminal fusions, resulting in the formation of rings and clumped chromosomes, and numerical ones, including hypo- and hyper-aneuploidy at metaphases, bridges, and laggards at the anaphase stage are observed. The percentage frequency of abnormalities in the shape of sperm heads is also found to be statistically significant over the controls. Besides this, zinc oxide nanoparticles are also found to affect the reproductive potential and embryo development as egg rafts obtained from the genetic crosses of ZnO nanoparticle-treated virgin females and normal males are small in size with a far smaller number of eggs per raft. The percentage frequencies of dominant lethal mutations indicated by the frequency of unhatched eggs are also statistically significant (p < 0.05) over the control. The induction of abnormalities in all of the three short-term assays studied during the present piece of work indicates the genotoxic potential of ZnO NPs, which cannot be labeled absolutely safe, and this study pinpoints the need to develop strategies for the protection of the environment and living organisms thriving in it.

The Roles of transformer-2 (tra-2) in the Sex Determination and Fertility of Riptortus pedestris, a Hemimetabolous Agricultural Pest.

In most holometabolous insects, transformer-2 (tra-2) is an auxiliary gene required for sex determination, exerting a crucial role in regulating sexual differentiation; however, the study of tra-2 in hemimetabolous insects remains very sparse and limited to just a few species. In this study, we investigated the sequence and expression profile of the tra-2 gene in the bean bug, Riptortus pedestris, an agricultural pest belonging to the Heteroptera order. Three non-sex-specific splicing isoforms of Rptra-2 were found, Rptra-2293, Rptra-2284, and Rptra-2299, which shared most exons and exhibited similar expression throughout all stages of development, with particularly elevated levels in the embryo, ovary, and testis. RNAi knockdown experiments revealed that the suppression of Rptra-2 in nymphs led to abnormal females, characterized the formation of male-specific external genital, and also caused longer nymph duration. Knockdown of the expression of the Rptra-2 gene in newly emergent virgin females would cause ovarian arrest, and injecting the 8th-day virgin females with dsRptra-2 also caused a noticeable decline in the offspring numbers. Conversely, in dsRptra-2-treated males, the testes maintained normal morphology but experienced impaired reproductive capacity, attributed to diminished sperm viability. These findings highlight the crucial role of Rptra-2 in the sex determination and fertility of R. pedestris, providing valuable insights into the sex determination mechanisms of hemimetabolous insects.

Effects of reproductive status on behavioral and neural responses to isolated pup stimuli in female California mice

The transition to motherhood in mammals is marked by changes in females’ perception of and responsiveness to sensory stimuli from infants. Our understanding of maternally induced sensory plasticity relies most heavily on studies in uniparental, promiscuous house mice and rats, which may not be representative of rodent species with different life histories. We exposed biparental, monogamous California mouse (Peromyscus californicus) mothers and ovariectomized virgin females to one of four acoustic and olfactory stimulus combinations (Control: clean cotton and white noise; Call: clean cotton and pup vocalizations; Odor: pup-scented cotton and white noise; Call + Odor: pup-scented cotton and pup vocalizations) and quantified females’ behavior and Fos expression in select brain regions. Behavior did not differ between mothers and ovariectomized virgins. Among mothers, however, those exposed to the Control condition took the longest to sniff the odor stimulus, and mothers exposed to the Odor condition were quicker to sniff the odor ball compared to those in the Call condition. Behavior did not differ among ovariectomized virgins exposed to the different conditions. Fos expression differed across conditions only in the anterior hypothalamic nucleus (AHN), which responds to aversive stimuli: among mothers, the Control condition elicited the highest AHN Fos and Call + Odor elicited the lowest. Among ovariectomized virgin females, Call elicited the lowest Fos in the AHN. Thus, reproductive status in California mice alters females’ behavioral responses to stimuli from pups, especially odors, and results in the inhibition of defense circuitry in response to pup stimuli.

The parenting hub of the hypothalamus is a focus of imprinted gene action.

Imprinted genes are subject to germline epigenetic modification resulting in parental-specific allelic silencing. Although genomic imprinting is thought to be important for maternal behaviour, this idea is based on serendipitous findings from a small number of imprinted genes. Here, we undertook an unbiased systems biology approach, taking advantage of the recent delineation of specific neuronal populations responsible for controlling parental care, to test whether imprinted genes significantly converge to regulate parenting behaviour. Using single-cell RNA sequencing datasets, we identified a specific enrichment of imprinted gene expression in a recognised "parenting hub", the galanin-expressing neurons of the preoptic area. We tested the validity of linking enriched expression in these neurons to function by focusing on MAGE family member L2 (Magel2), an imprinted gene not previously linked to parenting behaviour. We confirmed expression of Magel2 in the preoptic area galanin expressing neurons. We then examined the parenting behaviour of Magel2-null(+/p) mice. Magel2-null mothers, fathers and virgin females demonstrated deficits in pup retrieval, nest building and pup-directed motivation, identifying a central role for this gene in parenting. Finally, we show that Magel2-null mothers and fathers have a significant reduction in POA galanin expressing cells, which in turn contributes to a reduced c-Fos response in the POA upon exposure to pups. Our findings identify a novel imprinted gene that impacts parenting behaviour and, moreover, demonstrates the utility of using single-cell RNA sequencing data to predict gene function from expression and in doing so here, have identified a purposeful role for genomic imprinting in mediating parental behaviour.

Age-related changes in cuticular hydrocarbon bouquet and same-sex sexual behavior of mason bee males (Osmia cornuta and O. bicornis)

Finding a mate is the central task in the lives of many male insects. In many solitary bees, sexual competition between males is high due to monandry and a pronounced male-biased sex ratio. Males searching for females will inspect and mount any object of suitable size and habitus. Species, sex, and reproductive status are encoded in the bee’s bouquet of cuticular hydrocarbons (CHCs) and can only be identified at a short distance from the object encountered. In two species of mason bees, this CHC-based system for recognizing newly emerged, virgin females is not error-free. Newly emerged individuals of both sexes carry similar CHC bouquets, facilitating the confusion of newly emerged males with newly emerged, virgin females. Misidentification leads to same-sex sexual behavior by males seeking a mate. However, individuals of both sexes modify their CHC bouquet sex-specifically within a few days. The changes in the bouquet prevent further sexual harassment. In addition, within 3 days of emergence, males begin to release species-specific carboxylic acid esters, which may act as courtship-inhibiting pheromones to extend the range of their sex-specific scent tag. Due to the pronounced protandry of both species, SSB is restricted to the early flight season, when females are not yet present, and imposes no apparent cost on the two males involved.

Population Genomics of the Mostly Thelytokous Diplolepis rosae (Linnaeus, 1758) (Hymenoptera: Cynipidae) Reveals Population-specific Selection for Sex.

In Hymenoptera, arrhenotokous parthenogenesis (arrhenotoky) is a common reproductive mode. Thelytokous parthenogenesis (thelytoky), when virgin females produce only females, is less common and is found in several taxa. In our study, we assessed the efficacy of recombination and the effect of thelytoky on the genome structure of Diplolepis rosae, a gall wasp-producing bedeguars in dog roses. We assembled a high-quality reference genome using Oxford Nanopore long-read technology and sequenced 17 samples collected in France with high-coverage Illumina reads. We found two D. rosae peripatric lineages that differed in the level of recombination and homozygosity. One of the D. rosae lineages showed a recombination rate that was 13.2 times higher and per-individual heterozygosity that was 1.6 times higher. In the more recombining lineage, the genes enriched in functions related to male traits ('sperm competition", "insemination", and "copulation" gene ontology terms) showed signals of purifying selection, whereas in the less recombining lineage, the same genes showed traces pointing towards balancing or relaxed selection. Thus, although D. rosae reproduces mainly by thelytoky, selection may act to maintain sexual reproduction.

Identification of sex pheromone in Macdunnoughia crassisigna Warren (Lepidoptera: Noctuidae) and field optimization of the sex attractant.

Sex pheromones have proven to be a viable tool for monitoring and controlling pests and is an important part of integrated pest management (IPM). The noctuid moth Macdunnoughia crassisigna Warren poses a significant threat as a defoliator pest, impacting soybean and cruciferous vegetable production and quality in East Asia. However, a lack of comprehensive knowledge about its sexual chemical signaling hampers the development of semiochemical-based IPM approaches for M. crassisigna. We first determined the mating rhythms of M. crassisigna. We then collected pheromones from the sex glands of virgin females at the mating peak and analyzed their components using gas chromatography-electroantennogram detection analysis. The results showed that three components elicited significant electrophysiological responses in male antennae. Gas chromatography-mass spectrometry analysis characterized these components as (Z)-7-dodecene acetate (Z7-12:OAc), (Z)-9-tetradecene acetate (Z9-14:OAc), and (Z)-11-hexadecen-1-ol (Z11-16:OH). Further field experiments indicated that the mixture of Z7-12:OAc and Z9-14:OAc at a ratio of 3:1 displayed significant attractivity to males, confirming its role as a putative sex pheromone of M. crassisigna. Long-term monitoring tests showed that traps baited with these pheromone lures effectively mirrored the population dynamics of M. crassisigna. This study successfully identified and validated the sex pheromone released by female M. crassisigna and formulated potent sex lures for field-based pest monitoring. These findings enriched our understanding of chemical communication in Noctuidae and laid a foundation for developing practical monitoring and control methods against M. crassisigna. © 2023 Society of Chemical Industry.

Sexually dimorphic oxytocin receptor-expressing (OXTR) neurons in the anteroventral periventricular nucleus (AVPV) in the postpartum female mouse are involved in maternal behavior.

Maternal care is crucial for the survival and development of offspring. Oxytocin modulates maternal behavior by binding to oxytocin receptors (OXTRs) in various parts of the brain. Previously, we showed that OXTRs are expressed in the anteroventral periventricular nucleus (AVPV) of female, but not male mice. Because the AVPV is involved in the regulation of maternal behavior and oxytocin enhances its induction, this finding leads to the hypothesis that the female specific population of OXTR neurons in the AVPV regulates maternal behavior. To address this hypothesis, OXTR-Venus reporter mice were used to assess if expression levels of OXTR in the AVPV are changed during the postpartum period. The total number of OXTR-Venus neurons was significantly greater in postpartum dams compared to virgin females. To assess efferent projections of the AVPV-OXTR neurons, a Cre-dependent fluorescent protein (tdTomato) expressing a viral vector was injected into one side of the AVPV of female OXTR-Cre mice. Fibers expressing tdTomato were found in hypothalamic areas containing oxytocin neurons (the supraoptic and paraventricular nuclei) and the midbrain areas (the ventral tegmental area and periaqueductal gray) that are involved in the regulation of maternal motivation. To assess if activity of the AVPV-OXTR neurons is involved in the regulation of maternal behaviors, a chemogenetic approach was employed. Specific inhibition of activity of AVPV-OXTR neurons completely abolished pup retrieval and nest building behaviors. Collectively, these findings demonstrate that AVPV-OXTR neurons in postpartum female mice constitute an important node in the neural circuitry that regulates maternal behavior.

Effects of Loligo Squid Ink on Sexual Arousal Parameters in D-Galactose-Induced Aging Male Mice

Squid ink is known to contain many bioactive properties such as antioxidant, anticancer activity, antimicrobial activity, and anti-inflammatory activity. Through its antioxidant properties squid was suggested to have therapeutic potential for sexual function disorders. This study is an attempt to evaluate whether squid ink has therapeutic benefits against age-related decreases in sexual arousal in D-galactose-induced aging male mice. Four groups of male mice were treated as follows. Group-1 received only standar food but no D-galactose induction nor squid ink given. Group-2 received D-galactose induction but not squid ink. Group-3 and group-4 received D-galactose induction and squid ink at the dose of 40 and 100 ml/kg body weight respectively. After 35 days of treatment, the test mice were mated with estrous virgin females to determine their levels of sexual arousal. The results, Loligo squid ink extract at a dose of 100 ml/kg body weight significantly enhances sexual arousal parameter values in the D-galactose-induced aging mouse model. However, the recovery rate did not achieve nor surpassed the parameter values of sexual arousal in normal mice. It suggests that Loligo squid ink has the potential to prevent damage to sexual function in males but is less effective in restoring it.

Thermal tolerance in Spodoptera frugiperda: Influence of age, sex, and mating status

Temperature plays a key role in shaping the physiology and behavior of ectotherms where responses can depend on age, sex and ontogeny. We investigated the effects of age, sex and mating status on thermal tolerance of Spodoptera frugiperda 3-, 6- and 9-days old adults heat shocked at adult, pupal and larval stages, at 40 °C for 2 h. Our results showed varied significant critical thermal maxima across mating status, age, sex and life stage in tested insects after heat shock. The virgin females CTmax increased with age while it fluctuated in males and 6 days old virgin females had higher CTmax than males. The 3 day old mated females had the highest heat tolerance while 6 days old virgin males the lowest heat tolerance. There was no significant difference in CTmax recorded between virgin males and females aged 3 and 9 days as well as 3, 6 and 9 day mated males and females. There was also no significant interaction between mating status and sex but there was a significant interaction effect between life stage and age. Mated males had higher CTmax than females across all heat shocked developmental stages. The results show a high level of fitness and survival in S. frugiperda females, which may be advantageous in invasion. This study also showed “carry over” effects in adults heat shocked at juvenile stage, with aged adults showing decline in CTmax. This study suggests that plasticity of thermal tolerance may be an important approach for S. frugiperda invasion.

Effects of mating on female reproductive physiology in the insect model, Rhodnius prolixus, a vector of the causative parasite of Chagas disease.

The blood-sucking hemipteran Rhodnius prolixus is one of the main vectors of Chagas disease, a neglected tropical disease that affects several million people worldwide. Consuming a blood meal and mating are events with a high epidemiological impact since after each meal, mated females can lay fertile eggs that result in hundreds of offspring. Thus, a better knowledge of the control of R. prolixus reproductive capacity may provide targets for developing novel strategies to control vector populations, thereby reducing vector-host contacts and disease transmission. Here, we have used a combination of gene transcript expression analysis, biochemical assays, hormone measurements and studies of locomotory activity to investigate how mating influences egg development and egg laying rates in R. prolixus females. The results demonstrate that a blood meal increases egg production capacity and leads to earlier egg laying in mated females compared to virgins. Virgin females, however, have increased survival rate over mated females. Circulating juvenile hormone (JH) and ecdysteroid titers are increased in mated females, a process mainly driven through an upregulation of the transcripts for their biosynthetic enzymes in the corpus allatum and ovaries, respectively. Mated females display weaker locomotory activity compared to virgin females, mainly during the photophase. In essence, this study shows how reproductive output and behaviour are profoundly influenced by mating, highlighting molecular, biochemical, endocrine and behavioral features differentially expressed in mated and virgin R. prolixus females.

Conserved Odorant Receptors Involved in Nonanal-Induced Female Attractive Behavior in Two Spodoptera Species.

Moths rely on plant volatiles to locate appropriate plants for feeding and laying eggs. While extensive research has been conducted on the global agricultural pests, Spodoptera frugiperda and Spodoptera litura, their molecular mechanisms for detecting plant volatiles remain mostly unknown. Here, we have demonstrated that nonanal, a common plant volatile, is attractive for both virgin and gravid females of the two species. Second, we have identified a conserved odorant receptor clade (SfruOR47 clade) that is primarily tuned to nonanal. Finally, by three-dimensional (3D) structure prediction, molecular docking, and site-directed mutagenesis, we have revealed that the His57 and Glu61 residues, also shared by other six orthologous ORs, are essential for nonanal binding in SfruOR47 and SlituOR9, indicating the conserved structure and function of ORs in the SfruOR47 clade. These findings offer novel insights into the molecular mechanisms and evolutionary aspects of moth behavior in response to plant volatiles.

Development Features of Ixodes ricinus × I. persulcatus Hybrids under Laboratory Conditions.

Widely distributed Ixodes ricinus and Ixodes persulcatus ticks transmit many pathogens of both medical and veterinary significance. The ranges of these tick species overlap and form large sympatric areas in the East European Plain and Baltic countries. It has previously been shown that crossing I. ricinus and I. persulcatus is possible, resulting in the appearance of sterile hybrids. In the present study, we analyzed the features of this hybrid's life cycle under laboratory conditions. For this purpose, virgin females of I. ricinus and I. persulcatus ticks were obtained in the laboratory, and hybrid generations of ticks were bred from the reciprocal crossings of these two tick species. According to our data, mating the females of I. ricinus and I. persulcatus with the males of another species leads to a decrease in the engorgement success of the females, a decrease in the number of hatched larvae, and the appearance of a hybrid generation in which both females and males are sterile. Under laboratory conditions at a constant room temperature and under natural daylight, the morphogenetic diapause of the engorged I. persulcatus larvae began in September. For I. persulcatus nymphs, it occurred earlier than for I. ricinus, in October and November, respectively. The hybrids generally repeated the features of the life cycle of the mother species.

Anatomy of male and female genitalia of Acanthoscelidesobtectus (Say, 1831) (Coleoptera, Chrysomelidae, Bruchinae) in interaction.

Armatures of the male intromittent copulatory structures have been surmised to increase male fitness by imposing physiological costs on female re-mating. Female kicking could, consequently, be a counterstrategy to avoid wounding or to prevent males from mating. The membranous endophallus of male Acanthoscelidesobtectus (Say, 1831) is armed with denticles. Checking if these denticles penetrate the wall of the female genital tract during copulation revealed that only the tip of the median lobe of the aedeagus is intromitted into the female genital opening during copulation. The everted endophallus extends over the full length of the ovipositor, and the spermatophore is placed in the bursa. Identification by means of light microscopy and Micro-CT of the exact relative position of male and female copulatory organs while mated confirmed that the denticles do not cause wounds in the vagina wall. Parts of the inner wall of the bursa copulatrix are covered with inward pointing denticles. Already mated females kick mounting males by vehement movements of their hind legs, thereby preventing mating. In contrast, virgin females usually accept the first male they encounter and terminate copulation by slower movements of their hind legs. The same applied to females who accepted re-mating the second day after the first copulation. Acanthoscelidesobtectus females kick males off to prevent rather than to terminate copulation. Copulatory structures as well as behaviour may have different functional roles in different beetle species, even within the Bruchinae.

WMel Wolbachia alters female post-mating behaviors and physiology in the dengue vector mosquito Aedes aegypti

Globally invasive Aedes aegypti disseminate numerous arboviruses that impact human health. One promising method to control Ae. aegypti populations is transinfection with Wolbachia pipientis, which naturally infects ~40–52% of insects but not Ae. aegypti. Transinfection of Ae. aegypti with the wMel Wolbachia strain induces cytoplasmic incompatibility (CI), allows infected individuals to invade native populations, and inhibits transmission of medically relevant arboviruses by females. Female insects undergo post-mating physiological and behavioral changes—referred to as the female post-mating response (PMR)—required for optimal fertility. PMRs are typically elicited by male seminal fluid proteins (SFPs) transferred with sperm during mating but can be modified by other factors, including microbiome composition. Wolbachia has modest effects on Ae. aegypti fertility, but its influence on other PMRs is unknown. Here, we show that Wolbachia influences female fecundity, fertility, and re-mating incidence and significantly extends the longevity of virgin females. Using proteomic methods to examine the seminal proteome of infected males, we found that Wolbachia moderately affects SFP composition. However, we identified 125 paternally transferred Wolbachia proteins, but the CI factor proteins (Cifs) were not among them. Our findings indicate that Wolbachia infection of Ae. aegypti alters female PMRs, potentially influencing control programs that utilize Wolbachia-infected individuals.

Morphological changes in female reproductive organs in the African monarch butterfly, host to a male-killing Spiroplasma.

Sexual selection and conflicts within and between sexes promote morphological diversity of reproductive traits within species. Variation in the morphology of diagnostic reproductive characters within species offer an excellent opportunity to study these evolutionary processes as drivers of species diversification. The African monarch, Danaus chrysippus (Linnaeus, 1758), is widespread across Africa. The species is polytypic, with the respective geographical ranges of the four colour morphs only overlapping in East Africa. Furthermore, some of the populations host an endosymbiotic bacterium, Spiroplasma, which induces son-killing and distorts the local host population sex-ratio, creating sexual conflicts between the females seeking to optimize their fecundity and the limited mating capacity of the rare males. We dissected females from Kenya, Rwanda and South Africa, where Spiroplasma vary in presence and prevalence (high, variable and absent, respectively), and conducted microscopy imaging of their reproductive organs. We then characterized the effect of population, female body size, and female mating status, on the size and shape of different genitalia characters of the D. chrysippus female butterflies. We showed that although the general morphology of the organs is conserved in D. chrysippus, female genitalia vary in size and shape between and within populations. The virgin females have smaller organs, while the same organs were expanded in mated females. Females from highly female-biased populations, where the male-killing Spiroplasma is prevalent, also have a larger area of their corpus bursae covered with signa structures. However, this pattern occurs because a larger proportion of the females remains virgin in the female-biased populations rather than because of male depletion due to the symbiont, as males from sex-ratio distorted populations did not produce significantly smaller nutritious spermatophores.

Allatotropic peptides modulate muscle contraction of the female reproductive system in Rhodnius prolixus (STÄL)

Allatotropin (AT) acts as a myoregulator at the level of the dorsal vessel (DV) and midgut (MG) in triatominae insects. Previous analyses of the expression of the AT receptor in Rhodnius prolixus showed that AT is expressed in the DV and MG, but also in the reproductive system in females. To further study the activity of AT on female reproductive organs we analyzed the response by adult females in different physiological conditions, including unfed (virgin and mated), and fed mated females (gravid), to doses ranging between 10-14 and 10-6M. Myoregulatory activity was evaluated in vivo, by recording independently the frequency of contractions of each organ after treatment. The results show that the effect of AT varies depending on the organs and on the physiological state of the female. Whilst unfed virgin females did not show response to the peptide for neither of the applied doses, the ovaries showed a differential response, presenting the highest frequency of contractions in gravid individuals. An increase in the frequency of contractions of the oviducts was only observed in mated females. Uterus and spermathecae responded in both gravid and mated females, with maximum activity in the latter. In the bursa, responses were only detected in gravid females. The differential response of the organs seems to be associated to particular moments along the reproductive cycle, such as with the spermathecae that reacted to AT in both unfed mated and gravid females, when the movement of spermatozoids is physiologically crucial. Testes and accessory glands of the male, expressed the mRNA of AT precursor, suggesting that the male would modulate the contractile behavior of the female reproductive system after copula. The ovaries also expressed AT mRNA suggesting the existence of a paracrine/autocrine system modulating muscle contraction.

Masculinizer gene controls male sex determination in the codling moth, Cydia pomonella

The molecular mechanisms of sex determination in moths and butterflies (Lepidoptera) with female heterogamety (WZ/ZZ) are poorly understood, except in the silkworm Bombyx mori. However, the Masculinizer (Masc) gene that controls male development and dosage compensation in B. mori, appears to be conserved in Lepidoptera, as its masculinizing function was recently confirmed in several moth species. In this work, we investigated the role of the Masc gene in sex determination of the codling moth Cydia pomonella (Tortricidae), a globally important pest of pome fruits and walnuts. The gene structure of the C. pomonella Masc ortholog, CpMasc, is similar to B. mori Masc. However, unlike B. mori, we identified 14 splice variants of CpMasc in the available transcriptomes. Subsequent screening for sex specificity and genetic variation using publicly available data and RT-PCR revealed three male-specific splice variants. Then qPCR analysis of these variants revealed sex-biased expression showing a peak only in early male embryos. Knockdown of CpMasc by RNAi during early embryogenesis resulted in a shift from male-to female-specific splicing of the C. pomonella doublesex (Cpdsx) gene, its downstream effector, in ZZ embryos, leading to a strongly female-biased sex ratio. These data clearly demonstrate that CpMasc functions as a masculinizing gene in the sex-determining cascade of C. pomonella. Our study also showed that CpMasc transcripts are provided maternally, as they were detected in unfertilized eggs after oviposition and in mature eggs dissected from virgin females. This finding is unique, as maternal provision of mRNA has rarely been studied in Lepidoptera.

Electromagnetic field exposure affects the calling song, phonotaxis, and level of biogenic amines in crickets

The electromagnetic field (EMF) is ubiquitous in the environment, constituting a well-known but poorly understood stressor. Few studies have been conducted on insect responses to EMF, although they are an excellent experimental model and are of great ecological importance. In our work, we tested the effects of EMF (50 Hz, 7 mT) on the cricket Gryllus bimaculatus: the male calling song pattern, female mate choice, and levels of biogenic amines in the brain. Exposure of males to EMF increased the number and shortened the period of chips in their calling song (by 2.7% and 5% relative to the control song, respectively), but not the sound frequency. Aged (3-week-old) females were attracted to both natural and EMF-modified male signals, whereas young (1-week-old, virgin) females responded only to the modified signal, suggesting its higher attractance. Stress response of males to EMF may be responsible for the change in the calling song, as suggested by the changes in the amine levels in their brains: an increase in dopamine (by 50% relative to the control value), tyramine (65%), and serotonin (25%) concentration and a decrease in octopamine level (by 25%). These findings indicate that G. bimaculatus responds to EMF, like stressful conditions, which may change the condition and fitness of exposed individuals, disrupt mate selection, and, in consequence, affect the species’ existence.Graphical

Mate Discrimination Using Chemical Cues by Male Guppies.

Males often perform mate choice with the aim of maximizing reproductive success. To identify profitable mates, the males of some animals are known to use visual and chemical cues derived from females. In this study, we aimed to examine mate discrimination by male guppies (Poecilia reticulata) using chemical cues received from females under different reproductive statuses, i.e., virgin females, pregnant females, females after copulation with another male, and post-partum females. We conducted a dichotomous choice experiment for each combination of chemical stimuli from females under different reproductive statuses. In experiment 1, in which females were removed from water that was subsequently used as a chemical stimulus, male preferences did not differ significantly in all combinations of chemical stimuli from females under different reproductive statuses. However, in experiment 2, in which females remained within bottles containing the water used as a chemical stimulus, with the exception of one combination of chemical stimuli, significant differences in male preferences were detected for chemical stimuli derived from females under different reproductive statuses. Overall, males generally showed a preference for chemical stimulus received from females after copulation with other males. The findings of this study indicate that male guppies can discriminate the reproductive status of females based solely on chemical cues that may disappear or degenerate within a short period of time, thereby facilitating profitable mate choice.