Variation In Female Genitalia Research Articles

The Squamate Clitoris: A Review and Directions for Future Research.

The clitoris is a part of the genitalia of female amniotes that typically functions to stimulate sensory arousal. It usually consists of a small organ that is dimorphic and homologous to the penis. The developing amniote embryo forms a genital tubule, then sex hormones initiate a developmental cascade to form either a penis or clitoris. In squamates (lizards and snakes) the genital tubule develops into a paired hemiphallus structure called the "hemiclitores" in the female and the "hemipenes" in the male. The complex evolution of squamate hemipenes has been extensively researched since early discoveries in the 1800's, and this has uncovered huge diversity in hemipenis size, shape, and ornamentation (e.g., protrusions of spines, hooks, chalices, cups). In contrast, the squamate hemiclitoris has been conspicuously under investigated, and the studies that describe this anatomy are fraught with inconsistences. This paper aims to clarify the current state of knowledge of the squamate hemiclitoris, providing a foundation for further research on its morphology and functional role. We show that while several studies have described the gross anatomy of hemiclitores in lizards, comparative information is entirely lacking for snakes. Several papers cite earlier authors as having reported discoveries of the snake hemiclitores in vipers and colubrid snakes. However, our examination of this reveals only erroneous reports of hemiclitores in snakes and shows that these stem from misinterpretations of the true anatomy or species involved. An especially problematic source of confusion is the presence of intersex individuals in some snake populations; these form reproductively functional ovaries and a single hemipenis, with the latter sometimes mistaken for a hemiclitoris (the intersex hemipenis is usually smaller and less spinous than the male hemipenis). Further research is recommended to identify the defining anatomical features of the squamate hemiclitores. Such studies will form a vital basis of future comparative analyses of variation in female genitalia in squamates and other amniotes.

Vaginal Rejuvenation: A Review of Female Genital Cosmetic Surgery.

Female genital cosmetic surgery (FGCS) is a growing area within the field of gynecology with an increasing number of patients asking providers about these services. This review aims to increase the knowledge surrounding the types of FGCS performed, the outcomes and complications of these procedures, and the controversy surrounding FCGS. This study is a review of the most recent peer-reviewed articles and review articles as well as guidelines and recommendations of the American College of Obstetrics and Gynecology. Female genital cosmetic surgery is a broad term that encompasses multiple procedures including labiaplasty, vaginoplasty, clitoral hoodectomy, hymenectomy, labia majora augmentation, and G-spot amplification. Minimal data exist regarding the long-term outcomes and complications associated with these procedures. There is also a paucity of literature comparing FGCS to less invasive alternatives. Significant controversy exists regarding FGCS, given the known variation in female genitalia, lack of safety data, and concern for proprietary conflict with these procedures. Cosmetic gynecology surgery has become more popular in recent years, with few studies assessing the long-term benefits and harms of these treatments. Gynecologists should be aware of the lack of evidence supporting the effectiveness of FGCS in light of the growing marketing efforts and patient demand for these procedures.

The evolution of genital shape variation in female cetaceans.

Male genital diversification is likely the result of sexual selection. Female genital diversification may also result from sexual selection, although it is less well studied and understood. Female genitalia are complex among whales, dolphins, and porpoises, especially compared to other vertebrates. The evolutionary factors affecting the diversity of vaginal complexity could include ontogeny, allometry, phylogeny, sexual selection, and natural selection. We quantified shape variation in female genitalia using 2D geometric morphometric analysis, and validated the application of this method to study soft tissues. We explored patterns of variation in the shape of the cervix and vagina of 24 cetacean species (n = 61 specimens), and found that genital shape varies primarily in the relative vaginal length and overall aspect ratio of the reproductive tract. Extensive genital shape variation was partly explained by ontogenetic changes and evolutionary allometry among sexually mature cetaceans, whereas phylogenetic signal, relative testis size, and neonate size were not significantly associated with genital shape. Female genital shape is diverse and evolves rapidly even among closely related species, consistent with predictions of sexual selection models and with findings in invertebrate and vertebrate taxa. Future research exploring genital shape variation in 3D will offer new insights into evolutionary mechanisms because internal vaginal structures are variable and can form complex spirals.

Intraspecific and interspecific variation of female genitalia in two species of watersnake

The morphological differences in female genitalia within and between species are little studied and poorly understood, yet understanding patterns of variation in female genitalia can provide insights into mechanisms of genital evolution. The present study aimed to explore the patterns of intraspecific and interspecific variation in female genitalia in two sister taxa of watersnake (Nerodia sipedon and Nerodia fasciata) that have similar genital shape. We used a geometric morphometric (GM) approach to study variation in shape of the vagina between and within two sister species. We examined genital shape in female watersnakes ranging from small, sexually immature females to large reproductive females that had recently given birth. We found that shape variation of genitalia is strongly correlated with body size, where larger but not smaller females have a bifurcation in the vagina. However, we also found significant shape variation in the structure of the vagina between the two species, where N. fasciata has narrower genitalia with more prominent bifurcation, whereas N.sipedon has wider genitalia with less marked bifurcation. Using GM allowed us to detect significant differences in genital shape that were not apparent upon visual examination alone, suggesting that shape variation in female genitalia may be greater than previously assumed. Additional study of morphological differences in male reproductive organs for these species would help to determine whether there has been genital co-evolution, and potentially mechanical reproductive isolation, in these two closely-related and occasionally sympatric species. © 2013 The Linnean Society of London.

Sexual selection and genital evolution

AbstractMale genitalia show patterns of divergent evolution, and sexual selection is recognised as being responsible for this taxonomically widespread phenomenon. Much of the empirical support for the sexual selection hypothesis comes from studies of insects. Here, I synthesise the literature on insect genital evolution, and use this synthesis to address the debate over the mechanisms of selection most likely to explain observed patterns of macroevolutionary divergence in genital morphology. Studies of seven insect orders provide evidence that non‐intromittent genitalia are subject to sexual selection through their effects on mating success, while intromittent genitalia are subject to selection through their effects on fertilisation success. However, studies that use quantitative methods to analyse the form of selection are necessary to identify the mechanisms of sexual selection involved. Phylogenetic analyses from diverse taxonomic groups confirm that divergence in male genital morphology can be predicted from variation in the opportunity for sexual selection. Much debate revolves around the importance of female choice and sexual conflict in the evolution of male genitalia, the resolution of which lies in economic studies of mating interactions and in recognising sexual selection as a continuum between male competition, sexual conflict and female choice. The species isolating lock‐and‐key hypothesis is frequently dismissed as unimportant in genital evolution because in part of a perceived lack of variation in female genitalia across species. Increasingly, however, studies report species‐specific variation in female genital morphology and its coevolutionary divergence with male genital morphology. Contemporary views recognise a continuum between female choice that enforces species isolation and female choice that targets variation in male quality within populations, placing lock‐and‐key processes into the realm of sexual selection. Distinguishing between species‐isolating and directional forms of female choice will require studies that examine both the tempo and mode of divergence, both within and among species.

Visual depictions of female genitalia differ depending on source

Very little research has attempted to describe normal human variation in female genitalia, and no studies have compared the visual images that women might use in constructing their ideas of...