Inclusion of genital, sexual, and gender diversity in human reproductive teaching: impact on student experience and recommendations for tertiary educators.

Western societal norms have long been constrained by binary and exclusionary perspectives on matters such as infertility, contraception, sexual health, sexuality, and gender. These viewpoints have shaped research and knowledge frameworks for decades and led to an inaccurate and incomplete reproductive biology curriculum. To combat these deficiencies in reproductive systems-related education, our teaching team undertook a gradual transformation of unit content from 2018 to 2023, aiming to better reflect real diversity in human reproductive biology. This initiative involved intentional modifications, including clear use of pronoun self-identification by staff. We addressed the historical lack of representation of genital variation and helped students interrogate oversimplified reproductive biology binaries. A novel assignment was also introduced, prompting students to apply reproductive physiology knowledge to propose innovative assisted reproductive technology solutions for diverse demographics. The collective impact of these innovations had a positive effect on student learning. With improved lecture content and inclusive language, the proportion of inclusive group assignment topics chosen by students more than doubled in 2021. By 2022, coinciding with assessment topic changes, the percentage of inclusive assignments topics surpassed 50%. Further development of laboratory activities on intersex genital variation and genital modification raised further understanding of genital, sexual, gender, and cultural diversity. While implementing these changes posed challenges, pushing both staff and students out of their comfort zones at times, collaboration with relevant organizations and individuals with lived experience of queer identity proved integral. Ultimately, these relatively simple adjustments had a substantial impact on student experiences and appreciation for diversity.NEW & NOTEWORTHY We outline the teaching innovations that we have implemented to improve inclusion of diversity in reproductive biology and physiology contexts. This includes improved representation of genital, sexual, and gender diversity considerations in the curriculum. There is a critical need for these innovations as how we teach fundamentally shapes the understanding of our future medical and health professionals and researchers and thus influences the quality of future medical care and research.

Role of nuclear and membrane estrogen signaling pathways in the male and female reproductive tract.

Estrogen signaling through the main estrogen receptor, estrogen receptor 1 (ESR1; also known as ERα), is essential for normal female and male reproductive function. Historically, studies of estrogen action have focused on the classical genomic pathway. Although this is clearly the major pathway for steroid hormone actions, these hormones also signal through rapid non-classical effects involving cell membrane actions. Reports of rapid effects of estrogens extend for more than half a century, but recent results have expanded understanding of the identity, structure, function and overall importance of membrane receptors in estrogen responses. Key findings in this field were the immunohistochemical detection of ESR1 in cell membranes and demonstration that a portion of newly synthesized ESR1 is routed to the membrane by palmitoylation. These receptors in the membrane can then signal through protein kinases and other mechanisms following ligand binding to alter cell function. Another crucial advance in the field was development of transgenic mice expressing normal amounts of functional nuclear ESR1 (nESR1) but lacking membrane ESR1 (mESR1). Both male and female transgenic mice lacking mESR1 were infertile as adults, and both sexes had extensive reproductive abnormalities. Transgenic mice lacking mESR1 were highly protected from deleterious effects of neonatal estrogen administration, and estrogen effects on the histone methyltransferase Enhancer of Zeste homolog 2 that are mediated through mESR1 could have significant effects on epigenetic imprinting. In summary, signaling through mESR1 is essential for normal male and female reproductive function and fertility, and is a critical enabler of normal estrogen responses in vivo. Although the precise role of mESR1 in estrogen responses remains to be established, future research in this area should clarify its mechanism of action and lead to a better understanding of how mESR1 signaling works with classical genomic signaling through nESR1 to promote full estrogenic responses.

Interstitial cells: regulators of smooth muscle function.

Smooth muscles are complex tissues containing a variety of cells in addition to muscle cells. Interstitial cells of mesenchymal origin interact with and form electrical connectivity with smooth muscle cells in many organs, and these cells provide important regulatory functions. For example, in the gastrointestinal tract, interstitial cells of Cajal (ICC) and PDGFRα(+) cells have been described, in detail, and represent distinct classes of cells with unique ultrastructure, molecular phenotypes, and functions. Smooth muscle cells are electrically coupled to ICC and PDGFRα(+) cells, forming an integrated unit called the SIP syncytium. SIP cells express a variety of receptors and ion channels, and conductance changes in any type of SIP cell affect the excitability and responses of the syncytium. SIP cells are known to provide pacemaker activity, propagation pathways for slow waves, transduction of inputs from motor neurons, and mechanosensitivity. Loss of interstitial cells has been associated with motor disorders of the gut. Interstitial cells are also found in a variety of other smooth muscles; however, in most cases, the physiological and pathophysiological roles for these cells have not been clearly defined. This review describes structural, functional, and molecular features of interstitial cells and discusses their contributions in determining the behaviors of smooth muscle tissues.

Transfer- or 'transmission'-RNA fragments? The roles of tsRNAs in the reproductive system.

Transfer-RNAs (tRNAs) help ribosomes decode mRNAs and synthesize proteins; however, tRNA fragments produced under certain conditions, known as tRNA-derived small RNAs (tsRNAs), have been found to play important roles in pathophysiological processes. In the reproductive system, tsRNAs are abundant in gametes and embryos and at the maternal-fetal interface, as well as in microvesicles like epididymosomes, seminal plasma exosomes, and syncytiotrophoblast-derived extracellular vesicles. tsRNAs can affect gamete cell maturation, zygote activation, and early embryonic development. tsRNAs can transmit epigenetic information to later generations. In particular, exposure to environmental factors such as nutrition, isoproterenol, and poly(I:C) may allow tsRNAs to transfer information to the gametes or placenta to alter offspring phenotype. The underlying mechanisms of tsRNAs action include transposon silencing, translation regulation, and target mRNA degradation. Herein, we review the currently reported tsRNAs in the reproductive system, their validated functions, and potential roles. A better understanding of this field may help to provide useful recommendations or develop strategies to increase fertility and conception of healthy babies.

Reproductive and developmental toxicity screening study of an acetone extract of rosemary.

In 2017, JECFA requested reproductive and developmental toxicity studies to finalize an acceptable daily intake for solvent rosemary extracts. Thus, an OECD 421 reproductive/developmental toxicity study was conducted using an acetone rosemary extract that complied with JECFA and EFSA food additive specifications. Rosemary extract was provided to rats at dietary concentrations of 0 (control), 2100, 3600, or 5000 mg/kg, for 14 days before mating, during mating, and thereafter (throughout gestation and up to Lactation Day 13 for females) until necropsy. General toxicity (clinical signs, body weight, food consumption) and reproductive/developmental outcomes (fertility and mating performance, estrous cycles, anogenital distance, thyroid hormones, reproductive organ weights, thyroid histopathology) were assessed. There were no signs of general toxicity and no effects on reproduction; thus, the highest concentration tested (equivalent to mean daily intakes of 316 or 401 mg/kg bw/day [149 or 189 mg/kg bw/day carnosol and carnosic acid] for males and females, respectively) was established as the no-observed-adverse-effect level for general and reproductive toxicity. Dose-related reductions in T4 were observed for Day 13 pups (not seen on Day 4) but were not accompanied by thyroid weight changes or histopathological findings; further investigations are required to determine the biological relevance of these T4 reductions.

Structure of the reproductive system of the sexual generation of the endemic Arctic species Acyrthosiphon svalbardicum and its temperate counterpart Acyrthosiphon pisum (Hemiptera, Aphididae).

The Arctic aphids live briefly and must breed quickly to survive. Shortened life cycle, with only two generations: the stem mother and sexuales-oviparous females and males is an adaptation for optimal use of the short breeding period, which lasts from late July to the end of August. Using Acyrthosiphon svalbardicum, an endemic High Arctic aphid species, we describe the structure of the reproductive system of sexual morphs and compare with its temperate counterparts, in particular the model organism the pea aphid Acyrthosiphon pisum. Generally, the histological composition and ultrastructure of reproductive system of sexuales of A. svalbardicum is broadly similar to the reproductive systems described already in other species of aphids. The unique characters include in both oviparous females and males an enormous layer of the fat body, adhering to the structures of the internal reproductive system. The greatly enlarged accessory glands of males accumulate a heterogenous secretion composed of irregularly organized bunches of spicule-like structures of high electron density embedded in fine and coarse granular material. This material, unknown among temperate counterparts of A. svalbardicum, during mating is transported from the accessory glands of the male to its ejaculatory duct, where it is mixed with the ejaculate, and then is transferred to the spermatheca of the oviparous female.

Male Urogenital System Mapped Onto the Sensory Cortex: Functional Magnetic Resonance Imaging Evidence.

INTRODUCTION: The projection of the human male urogenital system onto the paracentral lobule has not previously been mapped comprehensively. AIM: To map specific urogenital structures onto the primary somatosensory cortex toward a better understanding of sexual response in men. METHODS: Using functional magnetic resonance imaging, we mapped primary somatosensory cortical responses to self-stimulation of the penis shaft, glans, testicles, scrotum, rectum, urethra, prostate, perineum, and nipple. We further compared neural response with erotic and prosaic touch of the penile shaft. MAIN OUTCOME MEASURE: We identified the primary mapping site of urogenital structures on the paracentral lobule and identified networks involved in perceiving touch as erotic. RESULTS: We mapped sites on the primary somatosensory cortex to which components of the urogenital structures project in men. Evidence is provided that penile cutaneous projection is different from deep penile projection. Similar to a prior report in women, we show that the nipple projects to the same somatosensory cortical region as the genitals. Evidence of differential representation of erotic and nonerotic genital self-stimulation is also provided, the former activating sensory networks other than the primary sensory cortex, indicating a role of "top-down" activity in erotic response. CLINICAL IMPLICATIONS: We map primary sites of projection of urogenital structures to the primary somatosensory cortex and differentiate cortical sites of erotic from nonerotic genital self-stimulation. STRENGTH & LIMITATIONS: To our knowledge, this is the first comprehensive mapping onto the primary somatosensory cortex of the projection of the components of the urogenital system in men and the difference in cortical activation in response to erotic vs nonerotic self-stimulation. The nipple was found to project to the same cortical region as the genitals. Evidence is provided that superficial and deep penile stimulation project differentially to the cortex, suggesting that sensory innervation of the penis is provided by more than the (pudendal) dorsal nerve. CONCLUSION: This study reconciles prior apparently conflicting findings and offers a comprehensive mapping of male genital components to the paracentral lobule. We provide evidence of differential projection of light touch vs pressure applied to the penile shaft, suggesting differential innervation of its superficial, vs deep structure. Similar to the response in women, we found nipple projection to genital areas of the paracentral lobule. We also provide evidence of differential representation of erotic and nonerotic genital self-stimulation, the former activating sensory networks other than the primary sensory cortex, indicating a role of top-down activity in erotic response. Allen K, Wise N, Frangos E, et al. Male Urogenital System Mapped Onto the Sensory Cortex: Functional Magnetic Resonance Imaging Evidence. J Sex Med 2020;17:603-613.

Nutrient conditions sensed by the reproductive organ during development optimize male fecundity in Drosophila.

Nutrient conditions affect the reproductive potential and lifespan of many organisms through the insulin signaling pathway. Although this is well characterized in female oogenesis, nutrient-dependent regulation of fertility/fecundity in males is not known. Seminal fluid components synthesized in the accessory gland are required for high fecundity in Drosophila males. The accessory gland is composed of two types of binucleated cells: a main cell and a secondary cell (SC). The transcription factors Defective proventriculus (Dve) and Abdominal-B (Abd-B) are strongly expressed in adult SCs, whose functions are essential for male fecundity. We found that gene expression of both Dve and Abd-B was down-regulated under nutrient-poor conditions. In addition, nutrient conditions during the pupal stage affected the size and number of SCs. These morphological changes clearly correlated with fecundity, suggesting that SCs act as nutrient sensors. Here, we provide evidence that Dve associates nutrient conditions with optimal reproductive potential in a target of rapamycin signaling-dependent manner.

Low temperature-induced aberrations in male and female reproductive organ development cause flower abortion in chickpea.

Chickpea (Cicer arietinum L.) is susceptible to low temperature (LT) at reproductive stage. LT causes flower abortion and delays pod set in chickpea until terminal drought becomes an issue, thereby decreasing yield potential. In chickpea, flower and anther/pollen development as well as LT-induced abnormalities on anther and pollen development are described inadequately. In the present manuscript, we report flower development stages, anther development stages, and aberrations in male gamete formation in chickpea under LT. Flower length was linearly correlated to flower and anther stages and can be used to predict these stages in chickpea. LT affected male gamete development in a flower/anther age-dependent manner where outcome ranged from no pollen formation to pollen sterility or no anther dehiscence to delayed dehiscence. In anthers, LT inhibited microsporogenesis, microgametogenesis, tapetum degeneration, breakage of septum and stomium, and induced pollen sterility. Whereas disruption of male function was the prime cause of abortion in flowers below vacuolated pollen stage, flower abortion was due to a combination of male and female reproductive functions in flowers with mature pollen. The study will help in elucidating mechanisms governing flower development, anther and pollen development, and tolerance/susceptibility to LT.

Primate microbial endocrinology: An uncharted frontier.

Gut microbial communities communicate bidirectionally with the brain through endocrine, immune, and neural signaling, influencing the physiology and behavior of hosts. The emerging field of microbial endocrinology offers innovative perspectives and methods to analyze host-microbe relationships with relevance to primate ecology, evolution, and conservation. Herein we briefly summarize key findings from microbial endocrinology and explore how applications of a similar framework could inform our understanding of primate stress and reproductive physiology and behavior. We conclude with three guiding hypotheses to further investigate endocrine signaling between gut microbes and the host: (a) host-microbe communication systems promote microbe-mediated stability, in which the microbes are using endocrine signaling from the host to maintain a functioning habitat for their own fitness, (b) host-microbe communication systems promote host-mediated stability, in which the host uses the endocrine system to monitor microbial communities and alter these communities to maintain stability, or (c) host-microbe systems are simply the product of coincidental cross-talk between the host and microbes due to similar molecules from shared ancestry. Utilizing theory and methodology for studying relationships between the microbiome, hormones, and behavior of wild primates is an uncharted frontier with many promising insights when applied to primatology.

Habitat amount partially affects physiological condition and stress level in Neotropical fruit-eating bats.

Hematological measures are increasingly being used to analyse the impact of several stressors on the physiological condition of animals. Landscape degradation and habitat loss impacts terrestrial and volant mammals occurrence, however rarely the effects of these factors on physiological conditions and stress levels were analyzed. Here, we measured several hematological parameters to analyse the impacts of habitat amount on the physiological condition (body condition and health status) and stress level of four species of Neotropical fruit-eating bats. We measured hematocrit, hemoglobin concentration and calculated the hemoglobin-hematocrit residuals (HHR) and mean cell hemoglobin concentration (MCHC), as well as the neutrophil to lymphocyte ratio (N/L ratio) of four common frugivores bat species (Artibeus lituratus, Artibeus planirostris, Sturnira lilium and Carollia perspicilatta). The bats were captured in 20 landscapes within the Atlantic Forest biodiversity hotspot, in a gradient from 10 to 85% of habitat amount. We tested the influence of habitat amount, species, sex and reproductive condition on the physiological variables. We fit GLM to each of the response variables and performed a model selection to identify the most plausible to explain the patterns. N/L ratio was negatively influenced by habitat amount, while the other variables were not related to habitat amount. Overall, we found that habitat loss apparently did not jeopardize the physiological condition of fruit-eating bats and that stress level apparently is not high enough to have any deleterious effect. We suggest that the increase in glucocorticoids, indirectly assessed by the N/L ratio, is a predictive, beneficial response, that allow these bats to cope efficiently with the stressors associated with habitat loss.

The evolution of relative trait size and shape: insights from the genitalia of dung beetles.

Insects show relatively little genital variation within species compared to extraordinary and often rapid diversification among species. It has been suggested that selection for reproductive isolation through differences in genital shape might explain this phenomenon. This hypothesis predicts that populations diverge faster in genital shape than in genital size. We tested this prediction in males from 10 dung beetle species with known phylogenetic relationships from the genus Onthophagus (Coleoptera: Scarabaeidae), including four species for which we were able to sample multiple populations. Specifically, we compared intra- and interspecific differentiation in shape and relative sizes of genitalia and calculated their respective evolutionary rates. We compared these rates to two similarly sized non-genital traits, the head and the fore-tibia. We found significant intraspecific variation in genital shape in all four species for which multiple populations were sampled, but for three of them we also identified significant relative size variation. We also found that genital shape evolved at higher rates than relative genital size. Genital shape evolved faster than head shape, but not fore-tibia shape. However, shapes of all measured structures evolved faster than their relative size. We discuss the functional constraints that may bias the developmental evolution of relative size and shape of genitalia and other morphological traits.

How Hot Are They? Neural Correlates of Genital Arousal: An Infrared Thermographic and Functional Magnetic Resonance Imaging Study of Sexual Arousal in Men and Women.

BACKGROUND: The few studies that have examined the neural correlates of genital arousal have focused on men and are methodologically hard to compare. AIM: To investigate the neural correlates of peripheral physiologic sexual arousal using identical methodology for men and women. METHODS: 2 groups (20 men, 20 women) viewed movie clips (erotic, humor) while genital temperature was continuously measured using infrared thermal imaging. Participants also continuously evaluated changes in their subjective arousal and answered discrete questions about liking the movies and wanting sexual stimulation. Brain activity, indicated by blood oxygen level-dependent (BOLD) response, was measured using functional magnetic resonance imaging. OUTCOMES: BOLD responses, genital temperature, and subjective sexual arousal. RESULTS: BOLD activity in a number of brain regions was correlated with changes in genital temperature in men and women; however, activation in women appeared to be more extensive than in men, including the anterior and posterior cingulate cortex, right cerebellum, insula, frontal operculum, and paracingulate gyrus. Examination of the strength of the correlation between BOLD response and genital temperature showed that women had a stronger brain-genital relation compared with men in a number of regions. There were no brain regions in men with stronger brain-genital correlations than in women. CLINICAL TRANSLATION: Our findings shed light on the neurophysiologic processes involved in genital arousal for men and women. Further research examining the specific brain regions that mediate our findings is necessary to pave the way for clinical application. STRENGTHS AND LIMITATIONS: A strength of the study is the use of thermography, which allows for a direct comparison of the neural correlates of genital arousal in men and women. This study has the common limitations of most laboratory-based sexual arousal research, including sampling bias, lack of ecologic validity, and equipment limitations, and those common to neuroimaging research, including BOLD signal interpretation and neuroimaging analysis issues. CONCLUSIONS: Our findings provide direct sex comparisons of the neural correlates of genital arousal in men and women and suggest that brain-genital correlations could be stronger in women. Parada M, Gérard M, Larcher K, et al. How Hot Are They? Neural Correlates of Genital Arousal: An Infrared Thermographic and Functional Magnetic Resonance Imaging Study of Sexual Arousal in Men and Women. J Sex Med 2018;15:217-229.

Characterization of Genital Dissatisfaction in a National Sample of U.S. Men.

Male genital satisfaction is an important aspect of psychosocial and sexual health. The Index of Male Genital Image (IMGI) is a new scale that measures perceptions of male genitalia. We aim to characterize genital satisfaction using the IMGI and correlate dissatisfaction with sexual activity. We conducted a nationally representative survey of non-institutionalized adults aged 18-65 years residing in the U.S. In total, 4198 men completed the survey and 3996 (95.2 %) completed the IMGI. Men reported highest satisfaction with the shape of their glans (64 %), lowest satisfaction with the length of their flaccid penis size (27 %), and neutrality with the scent of their genitals (44 %). No demographic characteristics (age, race, sexual orientation, education, location, and income) were significantly associated with genital dissatisfaction. Men who were dissatisfied with their genitals were less likely to report being sexually active (73.5 %) than those who were satisfied (86.3 %). Penetrative vaginal sex (85.2 vs. 89.5 %) and receptive oral intercourse (61.0 vs. 66.2 %) were reported less by dissatisfied men. Overall, most U.S. men were satisfied with their genitals; however, a subset (14 %) report low genital satisfaction, which included men of all ages, races, and socioeconomic groups. Low genital satisfaction is associated with a decrease in sexual activity. These results provide clinicians and health educators a baseline of genital satisfaction to provide education and reassurance.

Some assembly required: evolutionary and systems perspectives on the mammalian reproductive system.

In this review, we discuss the way that insights from evolutionary theory and systems biology shed light on form and function in mammalian reproductive systems. In the first part of the review, we contrast the rapid evolution seen in some reproductive genes with the generally conservative nature of development. We discuss directional selection and coevolution as potential drivers of rapid evolution in sperm and egg proteins. Such rapid change is very different from the highly conservative nature of later embryo development. However, it is not unique, as some regions of the sex chromosomes also show elevated rates of evolutionary change. To explain these contradictory trends, we argue that it is not reproductive functions per se that induce rapid evolution. Rather, it is the fact that biotic interactions, such as speciation events and sexual conflict, have no evolutionary endpoint and hence can drive continuous evolutionary changes. Returning to the question of sex chromosome evolution, we discuss the way that recent advances in evolutionary genomics and systems biology and, in particular, the development of a theory of gene balance provide a better understanding of the evolutionary patterns seen on these chromosomes. We end the review with a discussion of a surprising and incompletely understood phenomenon observed in early embryos: namely the Warburg effect, whereby glucose is fermented to lactate and alanine rather than respired to carbon dioxide. We argue that evolutionary insights, from both yeasts and tumor cells, help to explain the Warburg effect, and that new metabolic modeling approaches are useful in assessing the potential sources of the effect.

Keeping stem cells under control: New insights into the mechanisms that limit niche-stem cell signaling within the reproductive system.

Adult stem cells reside in specialized microenvironments, called niches, that maintain stem cells in an undifferentiated and self-renewing state. Defining and understanding the mechanisms that restrict niche signaling exclusively to stem cells is crucial to determine how stem cells undergo self-renewal while their progeny, often located just one cell diameter away from the niche, differentiate. Despite extensive studies on the signaling pathways that operate within stem cells and their niches, how this segregation occurs remains elusive. Here we review recent progress on the characterization of niche-stem cell interactions, with a focus on emerging mechanisms that spatially restrict niche signaling. Mol. Reprod. Dev. 83: 675-683, 2016 © 2016 Wiley Periodicals, Inc.

Androgenic Gland Implantation Induces Partial Masculinization in Marmorkrebs Procambarus fallax f. virginalis.

The androgenic gland in malacostracan crustacean species produces and secretes androgenic gland hormone, which is responsible for male sexual differentiation, such as the induction and development of male sexual traits, and in turn the suppression of female sexual traits. Marmorkrebs, Procambarus fallax forma virginalis, which was identified as the first parthenogenetic species in decapod crustaceans, produces only female offspring. In this study, in order to reveal whether the Marmorkrebs crayfish is sensitive to androgenic gland hormone, we transplanted an androgenic gland from a related congener, P. clarkii, to P. fallax f. virginalis. In androgenic gland-implanted specimens, partial masculinization was confirmed: the masculinization of several external sexual characteristics (i.e., thickening of the first and second pleopods; formation of reverse spines on the third and fourth pereopods) was detected, whereas that of internal sexual characteristics (e.g., the formation of ovotestes and male gonoducts) was not. Our results imply that P. fallaxf. virginalis still has sensitivity to the androgenic gland hormone and, at least partly, the hormone should be able to induce male characteristics, even in parthenogenetic Marmorkrebs.

Glucocorticoid Regulation of Reproduction.

It is well accepted that stress, measured by increased glucocorticoid secretion, leads to profound reproductive dysfunction. In times of stress, glucocorticoids activate many parts of the fight or flight response, mobilizing energy and enhancing survival, while inhibiting metabolic processes that are not necessary for survival in the moment. This includes reproduction, an energetically costly procedure that is very finely regulated. In the short term, this is meant to be beneficial, so that the organism does not waste precious energy needed for survival. However, long-term inhibition can lead to persistent reproductive dysfunction, even if no longer stressed. This response is mediated by the increased levels of circulating glucocorticoids, which orchestrate complex inhibition of the entire reproductive axis. Stress and glucocorticoids exhibits both central and peripheral inhibition of the reproductive hormonal axis. While this has long been recognized as an issue, understanding the complex signaling mechanism behind this inhibition remains somewhat of a mystery. What makes this especially difficult is attempting to differentiate the many parts of both of these hormonal axes, and new neuropeptide discoveries in the last decade in the reproductive field have added even more complexity to an already complicated system. Glucocorticoids (GCs) and other hormones within the hypothalamic-pituitary-adrenal (HPA) axis (as well as contributors in the sympathetic system) can modulate the hypothalamic-pituitary-gonadal (HPG) axis at all levels-GCs can inhibit release of GnRH from the hypothalamus, inhibit gonadotropin synthesis and release in the pituitary, and inhibit testosterone synthesis and release from the gonads, while also influencing gametogenesis and sexual behavior. This chapter is not an exhaustive review of all the known literature, however is aimed at giving a brief look at both the central and peripheral effects of glucocorticoids on the reproductive function.

The role of aedeagus size and shape in failed mating interactions among recently diverged taxa in the Drosophila mojavensis species cluster.

BACKGROUND: Investigating the evolution of species-specific insect genitalia is central to understanding how morphological diversification contributes to reproductive isolation and lineage divergence. While many studies evoke some form of sexual selection to explain genitalia diversity, the basis of selection and the mechanism of heterospecific mate exclusion remains vague. I conducted reciprocal mate pair trials in the Drosophila mojavensis species cluster to quantify the frequency of failed insemination attempts, historically referred to as pseudocopulation, between lineages with discrete size and shape differences of the male aedeagus. RESULTS: In cross-taxon matings aedeagus size had a significant effect on pseudocopulation frequencies, while aedeagus shape and genetic distance did not. The direction of the size difference was an important factor for successful mating. When females were mated to a cross-taxon male with a larger aedeagus than males from her own species, the pair could not establish a successful mating interaction. Females mated to cross-taxon males with a smaller aedeagus than conspecific males were able to establish the mating interaction but had issues disengaging at the end of the interaction. CONCLUSIONS: The results of this study support a role for aedeagus size in the male-female mating interaction, with a secondary role for aedeagus shape. In natural populations, mating failure based on aedeagus size could serve as an important reproductive isolating mechanism resulting in failed insemination attempts after both the male and female show a willingness to mate.