Male genital mutilation: an adaptation to sexual conflict

Male genital mutilation (MGM) takes several forms and occurs in about 25% of societies. This behavior has puzzled anthropologists, doctors and theologians for centuries, and presents an evolutionary challenge since it involves dangerous and costly surgery. I suggest that MGM is likely to reduce insemination efficiency, reducing a man's capacity for extra-pair fertilizations by impairing sperm competition. MGM may therefore represent a hard-to-fake signal of a man's reduced ability to challenge the paternity of older men who are already married. Men who display this signal of sexual obedience may gain social benefits if married men are selected to offer social trust and investment preferentially to peers who are less threatening to their paternity. Clitoridectomy and vaginal infibulation serve a parallel signaling function in women, increasing a husband's paternity certainty and garnering his increased investment. Especially in societies where paternity uncertainty and reproductive conflict are high, the social benefits of MGM as a signal may outweigh its costs. This ‘sexual conflict’ hypothesis predicts that MGM should be associated with polygyny, particularly when co-wives reside far apart, and that MGM should reduce the frequency of extramarital sex. MGM rituals should facilitate access to social benefits; they should be highly public, watched mainly by men, and performed by a nonrelative. I found support for these six predictions in two cross-cultural samples. I also examined an alternative hypothesis suggesting that MGM signals group commitment for collective action, particularly inter-societal warfare. Although other forms of male scarification fit this model, the distribution of MGM is not predicted by frequency of inter-societal warfare.     

Male genital tract chlamydial infection: implications for pathology and infertility

Chlamydia trachomatis infections are prevalent worldwide, but current research, screening, and treatment are focused on females, with the burden of disease and infertility sequelae considered to be a predominantly female problem. The prevalence of chlamydial infection, however, is similar in males and females. Furthermore, a role for this pathogen in the development of male urethritis, epididymitis, and orchitis is widely accepted. The role of Chlamydia in the development of prostatitis is controversial, but we suggest that Chlamydia is an etiological agent, with incidences of up to 39.5% reported in patients with prostatitis. Infection of the testis and prostate is implicated in a deterioration of sperm, possibly affecting fertility. Chlamydia infections also may affect male fertility by directly damaging the sperm, because sperm parameters, proportion of DNA fragmentation, and acrosome reaction capacity are impaired with chlamydial infection. Furthermore, the proportion of male partners of infertile couples with evidence of a Chlamydia infection is greater than that documented in the general population. An effect of male chlamydial infection on the fertility of the female partner also has been reported. Thus, the need for a vaccine to protect both males and females is proposed. The difficulty arises because the male reproductive tract is an immune-privileged site that can be disrupted, potentially affecting spermatogenesis, if inappropriate inflammatory responses are provoked. Examination of responses to infection in humans and in experimental animal models suggest that an immunoglobulin A-inducing vaccine will be able to target the male reproductive tract effectively while avoiding harmful inflammatory responses that may impair fertility.     

Female genital mutilation and cosmetic surgery: regulating non-therapeutic body modification

In the UK, female genital mutilation is unlawful, not only when performed on minors, but also when performed on adult women. The aim of our paper is to examine several arguments which have been advanced in support of this ban and to assess whether they are sufficient to justify banning female genital mutilation for competent, consenting women. We proceed by comparing female genital mutilation, which is banned, with cosmetic surgery, towards which the law has taken a very permissive stance. We then examine the main arguments for the prohibition of the former, assessing in each case both (a) whether the argument succeeds in justifying the ban and, if so, (b) whether a parallel argument would not also support a ban on the latter. We focus on the following arguments. Female genital mutilation should be unlawful because: (1) no woman could validly consent to it; (2) it is an oppressive and sexist practice; (3) it involves the intentional infliction of injury; (4) it causes offence. Our view is that arguments (3) and (4) are unsound and that, although arguments (1) and (2) may be sound, they support not only a ban on female genital mutilation, but also one on (some types of) cosmetic surgery. Hence, we conclude that the present legal situation in the UK is ethically unsustainable in one of the following ways. Either the ban on female genital mutilation is unjustified because arguments (1) and (2) are not in fact successful; or the law's permissive attitude towards cosmetic surgery is unjustified because arguments (1) and (2) are in fact successful and apply equally to female genital mutilation and (certain forms of) cosmetic surgery. The people of the countries where female genital mutilation is practised resent references to 'barbaric practices imposed on women by male-dominated primitive societies', especially when they look at the Western world and see women undergoing their own feminization rites intended to increase sexual desirability: medically dangerous forms of cosmetic plastic surgery, for instance....     

Male perineogenital anatomy and clinical applications in genital reconstructions and male-to-female sex reassignment surgery

To determine the possibility of providing alternative surgical techniques for male genital reconstruction and for male-to-female sex reassignment surgery, the authors undertook an anatomic investigation of the perineogenital region in male cadavers. Anatomic dissection was performed on 14 male adult human cadavers (fresh and formalin-preserved) studying the main afferent vessels to the anterior perineal region and their mean internal diameters: deep external pudendal artery (0.60 mm), superficial perineal artery (0.50 mm), and funicular artery (0.37 mm). We established their exact topography, together with vascular anatomic variations, main vascular anastomosis circuits (base of the penis, scrotal septum, and perineal fat and lateral spermatic-scrotal fascia), angiosomes, anatomy of the rectovesical septum cavity, and their "critical" key points of dissection. The authors discuss the clinical possibility of elevation of a "tree" of previously described paragenital-genital flaps including mainly those based on the terminal branches of the internal pudendal vascular system, the erectile tissue pedicled flaps, and finally, flaps of the external pudendal system. The authors indicate the concrete vascularization system for each flap.     

Male versus female genital alteration: Differences in legal,medical, and socioethical responses

The different legal, social, and medical approaches to ritually based male and female genital circumcision in the United States are highlighted in this article. The religious and historical origins of these practices are briefly examined, as well as the effect of changing policy statements by American medical associations on the number of circumcisions performed. Currently, no state or federal laws single out male circumcision for regulation. The tolerant attitudes toward male circumcision in law, medicine, and societal opinion stand in striking contrast to the attitudes of those disciplines toward even the least invasive form of female genital alteration. US law tacitly condones male circumcision by providing exemptions that are not available for other medical procedures, while criminalizing any similar or even less extensive procedure on females. The increase in immigration, over the past few decades, of people from countries in which female genital alteration is a cultural tradition has brought the issue to the United States. The medical profession's changing approach over time toward male circumcision is primarily responsible for such different legal and societal reactions toward female genital alteration.     

Male genital morphology and its influence on female mating preferences and paternity success in guppies

In internally fertilizing species male genitalia often show a higher degree of elaboration than required for simply transferring sperm to females. Among the hypotheses proposed to explain such diversity, sexual selection has received the most empirical support, with studies revealing that genital morphology can be targeted by both pre-and postcopulatory sexual selection. Until now, most studies have focused on these two episodes of selection independently. Here, we take an alternative approach by considering both components simultaneously in the livebearing fish, Poecilia reticulata. We allowed females to mate successively (and cooperatively) with two males and determined whether male genital length influenced the female's propensity to mate with a male (precopulatory selection, via female choice) and whether male genital size and shape predicted the relative paternity share of subsequent broods (postcopulatory selection, via sperm competition/cryptic female choice). We found no evidence that either episode of sexual selection targets male genital size or shape. These findings, in conjunction with our recent work exposing a role of genital morphology in mediating unsolicited (forced) matings in guppies, further supports our prior speculation that sexual conflict may be an important broker of genital evolution in this species.     

Male housefly (Musca domestica L.) genital system as a source of mating pheromone

Male volatile mating pheromone is released by male houseflies placed in close proximity to females or in contact with female hydrocarbon extract. The pheromone induces the aggregation of virgin females in the vicinity of the male. Preparations of macerated testicular and ejaculatory duct tissue exert a similar effect, and these organs are, apparently, the source of the pheromone. Such preparations are not attractive to males or mated females. The pheromone also appears to induce female receptivity, since females that are exposed to emanations from male system preparations show a quicker rate of pairing with males. The pheromone effect results from the testes and ejaculatory ducts acting together, as preparations of each of these alone are inactive. Pheromone activity is age dependent and the greatest female reaction is observed when tissues of 6–10-day old males are used.     

Male germ cell apoptosis and epigenetic histone modification induced by Tripterygium wilfordii Hook F

Multiglycosides of Tripterygium wilfordii Hook f (GTW), a Chinese herb-derived medicine used as a remedy for rheumatoid arthritis, are considered to be a reversible anti-fertility drug affecting the mammalian spermatids. However, the mechanism behind this effect is still unknown. To study the possible mechanism behind the impact of GTW on spermatogenesis, we administered 4 groups of 4-week-old male mice with different doses of GTW. We found a dose-dependent decrease in the number of germ cells after 40 days of GTW treatment, and an increase in apoptotic cells from the low-dose to the high-dose group. During this same period the dimethylated level of histone H3 lysine 9 (H3K9me2) in GTW-treated testes germ cells declined. Additionally, spermatogonial stem cells (SSCs) from 6-day-old mice were isolated to evaluate the possible effect of GTW or triptolide on development of SSCs. We found a significantly higher incidence of apoptosis and lower dimethylation level of H3K9me2 in the SSCs of GTW or triptolide treatment than in controls. Thus, these data suggest that the GTW-induced apoptosis might be responsible for the fertility impairment in mice. This damage could be traced back to the early stages of spermatogenesis. GTW also affected the epigenetic modification of H3K9 in spermatogenesis. Molecular dynamics simulation suggested that triptolide and dimethylated or trimethylated H3K9 might have similar interaction mechanisms with EED (embryonic ectoderm development). These candidate activation mechanisms provide the first glimpse into the pathway of GTW-induced gonad toxicity, which is crucial for further research and clinical application.     

Male genital homology based on musculature originating from the tegumen in snout moths (Lepidoptera: Pyraloidea)

The homology and terminology of the sclerotized structures, specifically the uncus and gnathos, formed by the fused segments caudal to the ninth abdominal segment in males of Lepidoptera, specifically in the Pyraloidea, have been confused in the literature. Based on comparative morphology of sclerotized structures and musculature, the uncus, scaphium, gnathos, and subscaphium are defined and described for stabilization in future systematic studies. Muscles IX–X (ex) and IX–X (int) are associated with these sclerotized structures and attached to the tegumen anteriorly. They are present in most of the species examined and are consistently topologically constrained in their origins and insertions; no differences were observed at the familial level. Muscle IX–X (int) is lacking in Pyralinae (Pyralidae) and this condition is hypothesized to be derived independently and an autapomorphy for this subfamily. The unique subteguminal processes of the Schoenobiinae are structures independent of the gnathos contrary to previous thought, and are instead associated with the valvae.     

The prenatal genotype-dependent modification by glucocorticoids of the morphometric characteristics of the genital system in mice and rats

Morphometric parameters of the reproductive system have been studied in adult males of four inbred mouse strains and two outbred rat strains after injection of corticosteroids into their mothers at 16 and 18 day of pregnancy. Significant interstrain difference in weight of sex glands was observed. Prenatal injection of corticosteroids decreased high values of features and increased low ones. Hence, the level of corticosteroids during prenatal development plays an important part in regulation of morphometric parameters of the reproductive system of adult rodents. The pattern of action depends on the genotype of an animal and may change under the influence of selection.     

Male genital system and spermiogenesis of Nanorchestes amphibius (Acari: Endeostigmata: Nanorchestidae): anatomy,histology, and evolutionary implications

In the present article the anatomy and histology of the male genital system of an endeostigmatid mite are described for the first time. The Endeostigmata probably are a paraphyletic group supposed to include the most primitive actinotrichid mites. In Nanorchestes amphibius, the testis comprises a paired germinal region connected with an unpaired glandular region. In the germinal region, spermiogenesis takes place in cysts of a somatic cell containing germ cells representing the same developmental stage. In the lumen of the glandular region, the spermatozoa are stored together with secretions of the glandular epithelium. These secretions are probably involved in the formation of spermatophores. From the glandular region, spermatozoa and secretions are released into the vasa deferentia that histologically can be divided into three sections, beginning with a short paired region with strong circular muscles serving as a sphincter, continuing with a paired proximal zone, followed by a short unpaired distal section. The distal vas deferens leads into the chitinous, unpaired ductus ejaculatorius which is followed by the progenital chamber. The ductus ejaculatorius is composed of a proximal section and a proximal, central, and anterior chamber. It is accompanied by a complex system of muscles and sclerites probably involved in the formation and ejaculation of the spermatophore. A similar organization can also be found in Prostigmata, but not in Oribatida. Anterior to the progenital chamber is located a paired accessory gland that probably produces a lipid secretion. Spermiogenesis is characterized by disintegration of the nuclear envelope, condensation of chromatin, and extensive reduction of the amount of sperm cell cytoplasm. The mature aflagellate, U-shaped spermatozoa are simple in structure and lack mitochondria and an acrosome complex. The results do not support the current view that Nanorchestidae are more closely related to Sarcoptiformes, i.e., Oribatida and Astigmata, than to Prostigmata.