Female Reproductive Maturation Research Articles

Effect of prolonged photoperiod on growth, gonadal development, sex ratio, and skin coloration of red tilapia (O. mossambicus × O. urolepis hornorum)

AbstractFarming of red tilapia is one promising direction in aquaculture. The objective of this study was to investigate the impact of long-day photoperiod on the growth performance, reproductive parameters, maturity, sex ratio, β-carotene content, and skin coloration of red tilapia. Early life larvae were allocated into three treatment groups in triplicates: T1 = control group (12L:12D), T2 = long-day group (18L:6D), and T3 = continuous illumination group (24L:0D) for 90 days. By the end of the experiment, gonadosomatic index (GSI), relative fecundity, steroid hormones, maturity stages, sex ratio, and ovarian and testicular histology were examined; also, growth performance, survival rate, skin color, and total β-carotene content were measured. The results indicated that GSI% and serum testosterone (T) in T3 group significantly increased with greater amount of spermatozoa of male fish. Also, growth parameters and HSI% in female fish displayed significantly increased for T3 group. Females in group T2 showed significant elevation in GSI%, relative fecundity, and estradiol (E2) with higher number of mature stage. Continuous light group (T3) showed shifted male sex ratio, while female percentage was higher in T2 group. The total β-carotene content of T3 group showed significant elevation with less number of black spots. This study demonstrated that continuous light manipulation during red tilapia early life could stimulate the growth and enhance coloration by reducing black spots that significantly affects economic profitability. Long-day application was effective in female reproductive performance and maturity. This study also served as an important reference for red tilapia aquaculture.

Transcriptomic profiling of castes and of sexually and parthenogenetically produced reproductive females in the termite Cavitermes tuberosus

AbstractIn termites with a true worker caste, the development pattern splits up from early developmental stages: primary reproductives develop through the nymphal line, whereas workers and soldiers follow the apterous developmental line. In some species, such as Cavitermes tuberosus Emerson (Isoptera: Termitidae, Termitinae), secondary reproductives (or neotenics) may also develop through the nymphal line from a transitional stage called aspirant. Aspirants originate mostly from automictic parthenogenetic reproduction. Therefore, C. tuberosus queens originate from sexual (primary queens) or parthenogenetic (neotenic queens) reproduction. A comparison of these two queen castes offers the possibility to better understand core molecular underpinnings of caste development and plasticity in termites. We investigated these molecular mechanisms by using high‐throughput Illumina RNA sequencing of pooled individuals. We first assembled the de novo reference transcriptome of C. tuberosus, and then identified the transcripts consistently co‐expressed across castes, sexes, and two alternative routes to female reproduction. Cavitermes tuberosus final transcriptome had 130 874 transcripts, N50 of 3398, and total length of 213 549 184 bp. We found that female reproductive maturation was characterized by gene expression down‐regulation: primary queens expressed fewer transcripts overall and had the greatest number of down‐regulated transcripts when compared to all other castes. In both secondary and primary queens, biological processes involved in muscle development and contraction, flight, and olfactory learning were enriched in the down‐regulated gene cluster. In contrast, processes related to reproductive development, insulin receptor signaling pathway, isoprenoid biosynthesis, and multiple metabolic processes were enriched among up‐regulated genes in primary queens. Finally, we found that 17% of all transcripts (21852) were differently co‐expressed when females from sexual and parthenogenetic origins were compared, even though the expression profile of core reproductive‐related gene clusters showed a similar trend in all reproductive females despite their origin. Our findings fit the genomic imprinting model predictions of a maternal effect that commonly regulates the expression of core reproductive genes in females from parthenogenetic and non‐parthenogenetic origins, whereas the expression of non‐reproductive genes varies.

Social drivers of maturation age in female geladas.

Female reproductive maturation is a critical life-history milestone, initiating an individual's reproductive career. Studies in social mammals have often focused on how variables related to nutrition influence maturation age in females. However, parallel investigations have identified conspicuous male-mediated effects in which female maturation is sensitive to the presence and relatedness of males. Here, we evaluated whether the more "classic" socioecological variables (i.e., maternal rank, group size) predict maturation age in wild geladas-a primate species with known male-mediated effects on maturation and a grassy diet that is not expected to generate intense female competition. Females delayed maturation in the presence of their fathers and quickly matured when unrelated, dominant males arrived. Controlling for these male effects, however, higher-ranking daughters matured at earlier ages than lower-ranking daughters, suggesting an effect of within-group contest competition. However, contrary to predictions related to within-group scramble competition, females matured earliest in larger groups. We attribute this result to either: 1) a shift to "faster" development in response to the high infant mortality risk posed by larger groups; or 2) accelerated maturation triggered by brief, unobserved male visits. While earlier ages at maturation were indeed associated with earlier ages at first birth, these benefits were occasionally offset by male takeovers, which can delay successful reproduction via spontaneous abortion. In sum, rank-related effects on reproduction can still occur even when socioecological theory would predict otherwise, and males (and the risks they pose) may prompt female maturation even outside of successful takeovers.

Effect of the Estrus Expression on Follicular and Luteal Morphofunctional Characteristics and Fertility in Bos indicus females Synchronized for FTAI

Background: Recent studies have been conducted with the aim of improving the fertility rates in the FTAI programs in beef females. The observation of the estrus expression constitutes an important indicator of fertility in zebu females. Therefore, this work has as an objective to evaluate the impact of the estrus expression on the follicular, luteal and fertility morphofunctional characteristics of Nelore females synchronized for FTAI.Materials, Methods & Results: Sixty five lactating female Nelore (Bos taurus indicus) were used. On a random day, denominated day 0 (D0), the 65 Nelore females received a progesterone-releasing device associated to the application of 2.0 mg of estradiol benzoate intramuscularly (IM). On D9, the progesterone-releasing intravaginal devices were removed and was administered 500 μg of cloprostenol sodium IM; 0.6 mg of estradiol cypionate IM and 300 UI of Equine Chorionic Gonadotropin IM. At this point, the animals were marked with a marking stick for the determination of the estrus expression. On D11 of the synchronization protocol, the animals were characterized in two groups: without estrus expression (WO/ ESTRUS) and with estrus expression (W/ ESTRUS). The evaluation of the follicle diameter (FOLD), of the follicle wall area (FOLA), of the follicle wall vascularization (FOLV) and the percentage of vascularization in the area of the preovulatory follicle wall (%FOLV) were conducted on D11 using B-mode ultrasonography and color Doppler and then the artificial inseminations were performed. The evaluation of the corpus luteum diameter (CLD), the total area of the corpus luteum (CLA), of the area of vascularization of the corpus luteum (CLV), of the percentage of vascularization of the in the area of the corpus luteum (% CLV) and the collection of blood for the evaluation of the serum levels of progesterone were carried out on D24. The analysis of the serum progesterone concentration were performed by the chemiluminescence method using the Access immunoassay systems Progesterone, with a sensitivity of 0.1 ng/mL. The diagnosis of gestation was carried out by transrectal ultrasonography on D45. The animals of the WITH ESTRUS group presented superior FOLD, FOLA, FOV (P < 0.05) averages to those presented by the cows of the WITHOUT ESTRUS group. In relation to the luteal characteristics, in the WITH ESTRUS group the cows exhibited averages for CLD, CLA, CLV and P4 significantly higher than those of the WITHOUT ESTRUS group. However, the bovines of the WITH ESTRUS group presented a % CLV similar to the presented by the females of the WITHOUT ESTRUS group. As for the fertility rates, there was difference between the experimental groups WITH ESTRUS and WITHOUT ESTRUS.Discussion: The present work demonstrated the impact of the estrus expression on the follicular morphological parameters, therefore in accordance with other studies. These authors show a relation between the estrus expression and levels of estradiol, which is directly related to the sperm transport in the female reproductive tract, oocyte maturation and fertilization directly affecting the fertility of females submitted to the FTAI program. Similarly, there was an interrelation between the estrus expression and the luteal morphological parameters, corroborating with the findings of some researches, where were verified higher luteal morphological parameters associated to higher conception rates in cows that demonstrated estrus behavior in the FTAI. Therefore, the estrus detection can be used as a tool to direct matings in synchronization protocols, promoting the identification of the animals with a higher probability of conception, owing to better follicular and luteal hemodynamic conditions.

Regulation of antimicrobial peptides by juvenile hormone and its receptor, Methoprene-tolerant, in the mosquito Aedes aegypti

The trade-off between reproduction and immunity has been established for a number of insect species. However, the regulatory mechanisms governing this event is not well understood. In the mosquito Aedes aegypti, the vector of dangerous human arboviral diseases, juvenile hormone (JH) is required for the female post-eclosion development and reproductive maturation. In this study, we have revealed the JH negative effect on the expression of immunity-related genes, such as antimicrobial peptides (AMPs), during the post-eclosion phase of the female mosquito gonadotrophic reproductive cycle. Mosquitoes treated with JH became more sensitive to microbial infection. Mosquitoes subjected to the RNA interference knockdown (RNAi) of the JH receptor, Methoprene-tolerant (Met), showed increased expression of several AMP genes. Met binds to the E-box-like recognition motifs in the regulatory region of the diptericin (Dpt) gene, indicating that JH can suppress the Dpt gene expression through its receptor Met. Hence, JH is involved in the modulation of immune responses during the post-eclosion phase of reproduction. The RNAi knockdown of the peptidoglycan recognition protein (PGRP-LC) led to a significant reduction of the Dpt transcript level, indicating the PGRP-LC activating role on this AMP gene. Thus, Dpt appeared to be under the dual regulation of both the JH and the immune deficiency (IMD) signaling pathways. Our study provides a better understanding of how JH regulates insect immunity in adult mosquitoes.

Production of embryos and a live offspring using post mortem reproductive material from bison (Bison bison bison) originating in Yellowstone National Park, USA

Bison from Yellowstone National Park (YNP) have an important genetic history. As one of the few wild herds of bison with no evidence of cattle DNA introgression and a large enough population to maintain genetic diversity, they are considered a conservation priority for the species. Unfortunately, there is a high prevalence of the zoonotic disease brucellosis in the herd. Part of the management strategy for controlling the disease and herd size in YNP is to remove bison from the population during the winter migration out of the park. This interagency management cull provides an opportunity to collect a large number of oocytes from a wild bison population for genetic banking and research purposes. During the winters of 2014–2018, which is the nonbreeding season for bison, oocytes were collected post mortem and used to determine the effects of donor reproductive maturity and pregnancy status on oocyte quality and in vitro fertilization (IVF) outcomes, and to demonstrate the feasibility of producing healthy offspring. Cumulus oocyte complexes (COCs) were placed into an in vitro embryo production (IVP) system, and on days 7, 7.5, and 8 of in vitro culture (Day 0 = day of in vitro fertilization) embryos were assessed for developmental stage and quality prior to vitrification. Embryos were then stored in liquid nitrogen until the breeding season when a subset were warmed, cultured for 6 h, evaluated for survival, and transferred to healthy bison recipients. There were no significant differences in the ability of recovered COCs to support blastocyst development based on female reproductive maturity or pregnancy status (juvenile 79/959 (8.2%) vs sexually mature 547/6544 (8.4%); non-pregnant 188/2302 (8.2%) vs pregnant 556/6122 (9.1%)). Following the transfer of 15 embryos to 10 recipients, one healthy female calf was born. This work demonstrates that live offspring can be generated from COCs collected from YNP bison post mortem in the non-breeding season, and that gamete recovery can be a valuable tool for conservation of valuable genetics for this species while mitigating diseases like brucellosis.

Female Power in Verreaux’s Sifaka (Propithecus verreauxi) Is Based on Maturity, Not Body Size

Conflicts between individuals are common among animals, with power dynamics often biased toward a particular sex. However, individuals across species exert power differently depending on the primary source of that power. Dominance-based power depends on fighting ability (e.g., greater body size) whereas leverage-based power depends on resources that cannot be taken by force (e.g., mating opportunities). Both can change in relative importance during development. We examined the development and base of female-biased power structures in Verreaux’s sifaka (Propithecus verreauxi) by analyzing the effects of reproductive maturity and body mass on intersexual conflict outcomes. We used data on four social groups at Ankoatsifaka Research Station in Kirindy Mitea National Park collected from 2007 to 2016, which included 483 decided agonistic encounters with both behavioral and morphometric data available. We used generalized linear mixed models to examine the effects of age, body mass, and female reproductive maturity on conflict outcome. Power relationships between mature females and males were unambiguously female biased. Female reproductive maturity, and not body mass, predicted intersexual conflict outcomes. Once reproductively mature, females almost never lost to males, except when females had not yet had an infant survive past weaning. Our results are thus consistent with the hypothesis that female leverage characterizes social structures of adult Verreaux’s sifaka more than female dominance. Future studies are needed to explore the influence of other sources of leverage and dominance, however. Similar studies in other primate species will clarify the role of what is often called “dominance” but may actually be leverage-based power.

Three Dimensional Secondary Ion Mass Spectrometry Imaging (3D-SIMS) of Aedes aegypti ovarian follicles.

The mobilization of nutrient reserves into the ovaries of Aedes aegypti mosquitoes after sugar-feeding plays a vital role in the female's reproductive maturation. In the present work, three-dimensional secondary ion mass spectrometry imaging (3D-SIMS) was used to generate ultrahigh spatial resolution (~1 μm) chemical maps and study the composition and spatial distribution of lipids at the single ovarian follicle level (~100 μm in size). 3D-Mass Spectrometry Imaging (3D-MSI) allowed the identification of cellular types in the follicle (oocyte, nurse and follicular cells) using endogenous markers, and revealed that most of the triacyglycerides (TGs) were compartmentalized in the oocyte region. By comparing follicles from water-fed and sugar-fed females (n=2), 3D-MSI-Time of Flight-SIMS showed that TGs were more abundant in ovarian follicles of sugar-fed females; despite relative sample reproducibility per feeding condition, more biological replicates will better support the trends observed. While the current 3D-MSI-TOF-SIMS does not permit MS/MS analysis of the lipid species, complementary LC-MS/MS analysis of the ovarian follicles aided tentative lipid assignments of the SIMS data. The combination of these MS approaches is giving us a first glimpse of the distribution of functionally relevant ovarian lipid molecules at the cellular level. These new tools can be used to investigate the roles of different lipids on follicle fitness and overall mosquito reproductive output.

Mating and social contact change egg production and longevity in adult females of the mirid Lygus hesperus

AbstractThere is frequently a tradeoff between fecundity and longevity, but the relationship is inconsistent across species and influenced by various exogenous and endogenous factors. Previous studies of Lygus hesperus Knight (Hemiptera: Miridae) established that egg production is promoted by insemination, at least temporarily, but little is known about the long‐term effects of mating and nonsexual interactions with conspecifics on egg production and female lifespan. To elucidate these relationships, survivorship and oviposition rate were tracked daily in females that were isolated or paired with a fertile male or another female throughout their adult lives. Mating rates were determined by postmortem examination. Results indicate that male‐specific stimuli accelerate female reproductive maturation, and that mating elevates oviposition rate. However, females paired with either a female or male companion had shortened lifespans, suggesting that social contacts exact a significant cost in this solitary species. Despite the negative impact of conspecific interactions and the finding that a singly mated female has sufficient sperm to fertilize a lifetime supply of eggs, many females were found to have mated more than once. Multiply mated females had higher sustained oviposition rates, lived longer, and had greater lifetime fecundities. Collectively, no strong evidence was found of a direct physiological link between fecundity and longevity, but environmental factors and mating were found to significantly influence both traits.

Reproductive dysfunction in females of endangered golden mahseer (Tor putitora) in captivity

The present study was undertaken to gain insight on the physiological basis underlying the constraints in attaining maturity of endangered golden mahseer (Tor putitora) in captivity. Selected hormone levels and stress biomarkers were analysed in wild and captive reared brooders to address the above objectives. As compared to their captive counterparts, plasma 17β-estradiol was significantly (p<0.05) higher in wild caught females. A concurrent trend was observed for plasma vitellogenin, aromatase, 17α, 20β-dihydroxy progesterone (17α, 20β DHP), luteinizing hormone (LH) and11-ketotestosterone (11-KT) indicating a weak hormone response in captive females that potentially hindered maturity. To the contrary, the plasma11-KT levels were not significantly different between wild and captive males. Plasma 17α, 20β DHP level was found significantly (p<0.05) higher in wild caught females compared to females reared in captivity. However, both males of wild and captivity registered significantly higher 17α, 20β DHP than captive females. Plasma 11-KT level was significantly higher in males compared to females. However, the captive females had higher level of 11-KT than captive males. Stress biomarkers viz., cortisol, superoxide dismutase (SOD) and glutathione peroxidase (GPx) were also estimated both in wild and captive brooders. There was no significant difference in plasma cortisol levels of wild and captive reared brooders. However, plasma GPx and SOD activity were significantly higher in captive reared T. putitora as compared to wild brooders counterpart manifesting prevailing oxidative stress in captivity. Overall results showed endocrine and stress differences between wild and captive reared brood fishes during early spawning period which highlighted the endocrine failure of female reproductive maturity in captivity.

Effects of a Neonatal Immune Challenge on Reproductive Development and Associated Behaviors in Siberian Hamsters (Phodopus sungorus)

Environmental stressors have the potential to disrupt early development in ways that could adversely impact fitness. Studies have demonstrated that animals exposed to postnatal lipopolysaccharide (LPS) show signs of delayed puberty, such as delayed vaginal opening and first estrus. This study investigated the effects of a neonatal immune challenge on subsequent adult reproductive physiology and behavior, and explored possible mediating mechanisms. Hamsters received LPS or saline injections on postnatal day (pnd) 3 and 5, as there is heightened sensitivity of the GnRH pulse generator at these time points. Female reproductive maturity was determined by monitoring for vaginal patency, beginning on pnd 25 and every five days thereafter until maturity. Male reproductive maturity was determined by using the left testis length and width to estimate testis weight beginning on pnd 25 and each subsequent week until reproductive maturity. At pnd 75 animals were placed in staged mating pairs with reproductively mature individuals of the opposite sex. Rejection, grooming and sniffing behaviors were scored for all females, and the lordosis quotient was calculated for receptive females. Mounting, intromission and ejaculation were scored in males. Preliminary data showed a decrease in food intake and body mass, as well as delay in reproductive maturity for animals treated with LPS. Female receptivity and other reproductive behaviors were varied by the LPS challenge. The results of this study contribute to a greater understanding of the behavioral responses to early immune challenges and possible ways in which animals may adjust to this common stressor.

Inhibition of female mating by male accessory gland substances in the ground beetle Leptocarabus procerulus

AbstractThe ground beetle Leptocarabus procerulus (Chaudoir) possesses seminal substances that have a physical function to form mating plugs and a physiological function to induce female refractory behaviour, which act together to hinder female remating. Little is known about the physiological properties of the substances inducing female refractory behaviour, especially with respect to their secretory organ, dose‐dependency, molecular characteristics and the effect of female maturity. By injecting male‐derived substances into females, substances that induce female refractory behaviour are shown to be produced in the male accessory gland but not in the testis. Injection of extracts from the accessory gland increases the female refractory period at moderate doses but not at lower or higher doses. By contrast, injection of extracts from the testis reduces the female refractory period at high doses. The lack of an effect of accessory gland substances at higher doses could be the result of an anomalous effect of unnaturally large doses of seminal products by direct injection, the toxicity of seminal substances that deter female responses, or counteraction by injected substances that promote female receptivity. The accessory gland substances lose their activity when heated, although the testis substances do not. Females without mature eggs tend to reject mating entirely, although variation in the number of mature eggs (one or more) is not associated with the female refractory period, indicating the limited effect of female reproductive maturity. These findings may help to clarify the physiological basis of the evolution of the elaborated male mating behaviour in L. procerulus.

Insights into the Prostanoid Pathway in the Ovary Development of the Penaeid Shrimp Penaeus monodon

The prostanoid pathway converts polyunsaturated fatty acids (PUFAs) into bioactive lipid mediators, including prostaglandins, thromboxanes and prostacyclins, all of which play vital roles in the immune and reproductive systems in most animal phyla. In crustaceans, PUFAs and prostaglandins have been detected and often associated with female reproductive maturation. However, the presence of prostanoid biosynthesis genes remained in question in these species. In this study, we outlined the prostanoid pathway in the black tiger shrimp Penaeus monodon based on the amplification of nine prostanoid biosynthesis genes: cytosolic phospholipase A2, hematopoietic prostaglandin D synthase, glutathione-dependent prostaglandin D synthase, prostaglandin E synthase 1, prostaglandin E synthase 2, prostaglandin E synthase 3, prostaglandin F synthase, thromboxane A synthase and cyclooxygenase. TBLASTX analysis confirmed the identities of these genes with 51-99% sequence identities to their closest homologs. In addition, prostaglandin F2α (PGF2α), which is a product of the prostaglandin F synthase enzyme, was detected for the first time in P. monodon ovaries along with the previously identified PUFAs and prostaglandin E2 (PGE2) using RP-HPLC and mass-spectrometry. The prostaglandin synthase activity was also observed in shrimp ovary homogenates using in vitro activity assay. When prostaglandin biosynthesis was examined in different stages of shrimp ovaries, we found that the amounts of prostaglandin F synthase gene transcripts and PGF2α decreased as the ovaries matured. These findings not only indicate the presence of a functional prostanoid pathway in penaeid shrimp, but also suggest a possible role of the PGF2α biosynthesis in shrimp ovarian development.

Genetic dissection of puberty in mice

Determining the neural mechanisms controlling gonadotrophin-releasing hormone (GnRH) release is of pivotal importance in understanding central control of reproductive physiology in vertebrates. Targeted genetic manipulation of kisspeptin and GPR54 neurons has provided new insights into the mechanisms modulating GnRH release and thereby regulating hypothalamic-pituitary-gonadal axis activity during reproductive maturation. While conditional ablation of the oestrogen receptor α gene in kisspeptin neurons results in a dramatic advancement of the onset of puberty in female mice, subsequent pubertal maturation is arrested in these animals, as they fail to acquire normal ovulatory cyclicity. These data suggest that two oestrogen receptor α-dependent mechanisms, one a 'brake' and the other an 'accelerator', are sequentially operated in kisspeptin neurons during pubertal development of female mice to gate and then to activate GnRH release. In a different experimental approach, we removed entire kisspeptin neurons from the mouse brain and thus from the neural circuits controlling reproduction. Surprisingly, the onset of puberty in females was unaffected by kisspeptin neuron ablation. Furthermore, the animals attained regular ovulatory cyclicity and were fertile. Consistent with this, female mice lacking neurons that express the kisspeptin receptor GPR54 were also fertile, suggesting female reproductive maturation in the absence of kisspeptin/GPR54 signalling. However, acute kisspeptin neuron ablation in adult mice inhibited fertility, indicating that there is developmental compensation for the loss of kisspeptin neurons during reproductive neural circuit formation. Finally, we showed that kisspeptin neurons become an indispensable part of reproductive neural circuitry in the mouse brain before postnatal day 20.

Ovarian development of Agrilus planipennis: effects of age and mating status and influence on attraction to host volatiles

AbstractEmerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a major pest of ash trees, Fraxinus spp. (Oleaceae), in North America. This study investigated the timing of reproductive development in female beetles and the influence of female reproductive maturity on attraction to host volatiles. Based on dissections of females of increasing age, females with access to males for mating, and thus presumed mated, developed mature eggs only after 18–24 days. In contrast, female beetles reared without access to males, and thus unmated, did not develop mature eggs at any age. Chemical analysis of cuticular hydrocarbons detected the contact sex pheromone, 9‐methyl‐pentacosane, in cohorts of females which were 8–9 days old and older, supporting previous research that this compound signals sexual maturity to males. Results from field‐trapping bioassays demonstrated that stage of female reproductive maturity influenced their attraction to host volatiles: females caught on traps baited with foliar volatiles contained eggs and ovarioles that were significantly less developed than those on traps baited with bark sesquiterpenes. However, our results revealed that females with immature stages of ovarioles and undeveloped eggs, such as those observed in unmated females, were rarely ever caught on traps baited with either of the host volatile lures. Further research on host compounds attractive to immature females is critical for early detection and possible control of A. planipennis populations during the extended pre‐oviposition period.

Proteomic Analysis of Tegument-Exposed Proteins of Female and Male Schistosoma japonicum Worms

The interplay between sexes is a prerequisite for female growth, reproductive maturation, and egg production, and the basis of schistosome pathopoiesis and propagation. The tegument is in direct contact with the host environment and its surface membranes are particularly crucial for schistosome survival in the definitive host. In this study, a streptavidin-biotin affinity purification technique combined with LC-MS/MS was used to analyze putative tegument-exposed proteins in female and male adult Schistosoma japonicum worms. In total, 179 proteins were identified in females and 300 in males, including 119 proteins common to both sexes, and 60 female biased and 181 male biased proteins. Some (e.g., serpin and CD36-like class B scavenger receptor) were involved in host-schistosome interactions, while some (e.g., gynecophoral canal protein) were important in the interplay between sexes. Gene Ontology analysis revealed that proteins involved in protein glycosylation and lysosome were highly expressed in females, while proteins involved in intracellular signal transduction, regulation of actin filament polymerization, and proteasome core complex were highly expressed in males. These results might elucidate physiological differences between the sexes. Our study provides new insights into schistosome growth and sexual maturity in the final host and permits the screening of vaccine candidates or drug targets for schistosomiasis.

How the evolutionary theory of aging can guide us in the search for aging genes

It is a stroke of irony that lifespan — the principal phenotype used to search for aging genes — is a terrible phenotype for genetic analysis. Lifespan has relatively low heritability under most conditions, and it is affected by chronic, age-related diseases that confound its use as a biomarker of aging. If the majority of aging genes are pleiotropic, as proposed by the evolutionary theory of aging, an opportunity is provided to identify these genes through the “back door,” using phenotypes that are more amenable to genetic analysis. To choose the pleiotropic phenotype for our studies, we went back more than 50 years to Williams [1], who, in his seminal paper, specified four “physiological expectations that follow from the theory,” two of which we applied: “Rapid individual development should be correlated with rapid senescence,” and, to specify a particular developmental phenotype, “The time of reproductive maturation should mark the onset of senescence.” Therefore, to search for genes that regulate lifespan, we looked in the other direction — for genes that govern reproductive maturation. We started our search for pleiotropic aging genes by evaluating the age of female sexual maturity in the highly diverse, 32-inbred strain panel provided by The Jackson Laboratory Nathan Shock Center. As predicted by the evolutionary theory of aging, age of vaginal patency (VP) correlated positively with lifespan across strains. Interestingly, it also correlated negatively with circulating IGF1. And, because, in the same 32 strains of mice, 6-month IGF1 levels also correlate negatively with lifespan [2], it is likely that IGF1 mediates a significant portion of the linkage of reproductive maturation with aging and lifespan. We tested this idea in a congenic C57BL/6J (B6) mouse that carries a portion of Chr 10 from the C3H/HeJ strain. In congenic females, circulating IGF1 was elevated and as predicted, age of VP was accelerated and lifespan was shortened. (In males, IGF1 was not elevated and lifespan was not shortened.) Thus, the stage was set to begin a search for pleiotropic genes that influence both female reproductive maturation and lifespan in the strain panel. Using haplotype association mapping, we identified three loci (Vpq1 [Chr 4], Vpq2 and Vpq3 [both on Chr 16]) that accounted for 76% of the variance in age of VP across strains. Again, IGF1 may be involved. Age of VP was delayed and circulating IGF1 was diminished in the B6.PWD–Chr 16 consomic strain, in which the PWD/PhJ Chr 16, carrying the late age of VP haplotype at Vpq3, replaces the B6 Chr 16, carrying an intermediate age of VP haplotype. Haplotypes of Vpq 3 also associated with differences in lifespan, strongly supporting the hypothesis that a gene at Vpq3 mediates an antagonistic relationship between age of VP and lifespan. We then used an arsenal of bioinformatic and genetic strategies to query Vpq3 for candidate genes, which ultimately designated nuclear receptor interacting protein 1 (Nrip1) as a strong candidate. NRIP1 is a regulator of nuclear receptors that have broad functions in regulating cell growth, cell death, and metabolism. Nrip1, as a transcriptional repressor of PGC-1α and β, could promote senescence by suppressing mitochondrial biogenesis [3]. Nrip1 null (−/−) mice are smaller and leaner, are resistant to high-fat diet-induced obesity, and show increased glucose tolerance and insulin sensitivity [4,5] — mimicking characteristics found in calorierestricted mice. We compared Nrip1 null mice with their normal littermates. Results verified the hypothesis — generated by genetic and bioinformatic analyses — that knocking out Nrip1 could significantly decrease IGF1 level and delay age of VP. Lifespan studies of Nrip1 null mice are in process. Additional work is necessary to verify Nrip1 as an aging gene that mediates an antagonistic relationship between female reproductive maturation and lifespan. But our present analysis does provide direct support for the hypothesis that genes that regulate IGF1 constitute an entire category of pleiotropic genes that influence both reproductive maturation and aging. Our results also suggest that genes such as Nrip1 — with highly pleiotropic effects on metabolism and cell turnover as well as on cell signaling and life history traits — are the types of genes that have the greatest impact on aging. Our work demonstrates that the utilization of pleiotropy in strategies informed by evolutionary theory is an effective approach in the search for genes that regulate aging.

Changes in Gene Expression Associated with Reproductive Maturation in Wild Female Baboons

Changes in gene expression during development play an important role in shaping morphological and behavioral differences, including between humans and nonhuman primates. Although many of the most striking developmental changes occur during early development, reproductive maturation represents another critical window in primate life history. However, this process is difficult to study at the molecular level in natural primate populations. Here, we took advantage of ovarian samples made available through an unusual episode of human–wildlife conflict to identify genes that are important in this process. Specifically, we used RNA sequencing (RNA-Seq) to compare genome-wide gene expression patterns in the ovarian tissue of juvenile and adult female baboons from Amboseli National Park, Kenya. We combined this information with prior evidence of selection occurring on two primate lineages (human and chimpanzee). We found that in cases in which genes were both differentially expressed over the course of ovarian maturation and also linked to lineage-specific selection this selective signature was much more likely to occur in regulatory regions than in coding regions. These results suggest that adaptive change in the development of the primate ovary may be largely driven at the mechanistic level by selection on gene regulation, potentially in relationship to the physiology or timing of female reproductive maturation.

Nutrient limitation results in juvenile hormone-mediated resorption of previtellogenic ovarian follicles in mosquitoes

Juvenile hormone (JH) is a central hormonal regulator of previtellogenic development in female Aedes aegypti mosquitoes. JH levels are low at eclosion and increase during the first day after adult emergence. This initial rise in JH is essential for female reproductive maturation. After previtellogenic maturation is complete, the mosquito enters a ‘state-of-arrest’ during which JH synthesis continues at a slower pace and further ovary development is repressed until a blood meal is taken. By examining the relationships between juvenile hormone, follicular resorption and nutrition in A. aegypti, we were able to define a critical role of JH during the previtellogenic resting stage. The rate of follicular resorption in resting stage mosquitoes is dependent on nutritional quality. Feeding water alone caused the rate of follicular resorption to reach over 20% by day 7 after emergence. Conversely, feeding a 20% sucrose solution caused resorption to remain below 5% during the entire experimental period. Mosquitoes fed 3% sucrose show rates of resorption intermediate between water and 20% sucrose and only reached 10% by day 7 after emergence. Follicular resorption is related to JH levels. Ligated abdomens separated from a source of JH (the corpora allata) showed an increase in resorption comparable to similarly aged starved mosquitoes (16%). Resorption in ligated abdomens was reduced to 6% by application of methoprene. The application of methoprene was also sufficient to prevent resorption in intact mosquitoes starved for 48h (14% starved vs. 4% starved with methoprene). Additionally, active caspases were localized to resorbing follicles indicating that an apoptotic cell-death mechanism is responsible for follicular resorption during the previtellogenic resting stage. Taken together, these results indicate that JH mediates reproductive trade-offs in resting stage mosquitoes in response to nutrition.

Reproductive delay in the female Cape ground squirrel (Xerus inauris)

Abstract We studied the simultaneous effects of social and environmental factors on the age of sexual maturity to identify the major determinants of reproductive delay in the cooperatively breeding female Cape ground squirrel (Xerus inauris). We verified inhibition of sexual maturity by monitoring reproductive behaviors and hormones (using a noninvasive fecal steroid hormone analysis) in prereproductive and reproductive females from 2 populations of squirrels found in southern Africa. We found that 2 social parameters hold the most influence on the timing of female sexual maturity; specifically, the number of adult breeding female group mates and related adult male group mates were associated with a substantial inhibition of female reproductive maturity. Subadult females in social groups with 0 or 1 adult breeding female became sexually mature significantly earlier than similar-aged females in social groups with ≥2 adult breeding females. Likewise, subadult females in social groups with <2 related adult m...