Androgens and masculinization of genitalia in the spotted hyaena (Crocuta crocuta). 2. Effects of prenatal anti-androgens.

Pregnant spotted hyaenas were treated with anti-androgens to interfere with the unusually masculine 'phallic' development that characterizes females of this species. The effects on genital morphology and plasma androgen concentrations of infants were studied during the first 6 months of life. Although there were consistent 'feminizing' effects of prenatal anti-androgen treatment on genital morphology in both sexes, such exposure did not produce males with extreme hypospadia, as it does in other species, nor did it produce females with a 'typical' mammalian clitoris and external vagina. 'Feminization' of males resulted in a penis with the morphological features of the hyaena clitoris, and 'feminization' of females exaggerated the sex differences that are typical of this species. The effects of treatment were present at birth and persisted for at least 6 months. Treatment of pregnant females with flutamide and finasteride also markedly reduced circulating concentrations of testosterone and dihydrotestosterone in maternal plasma during pregnancy. Plasma delta 4-androstenedione was reduced in the female, but not the male, infants of treated mothers, consistent with an epigenetic hypothesis previously advanced to explain hormonal 'masculinization' of females. The present 'feminizing' effects of prenatal anti-androgen treatment are consistent with contemporary understanding of sexual differentiation, which accounts for morphological variation between the sexes in terms of steroids. However, current theory does not account for the basic genital structure of females and the present data suggest that development of the male penis and scrotum, and the female clitoris and pseudoscrotum, in spotted hyaenas may involve both androgen-dependent and androgen-independent components.

Androgens and masculinization of genitalia in the spotted hyaena (Crocuta crocuta). 3. Effects of juvenile gonadectomy.

Studies involving the administration of anti-androgens to spotted hyaenas during fetal development have raised questions concerning the precise contributions of steroids to phallic growth in these animals. If gonadal androgens promote postnatal penile growth in males, the following would be expected: (a) a period of accelerated growth accompanying achievement of puberty, and (b) a marked reduction in adult penile size and density of penile spines after gonadectomy. If a similar androgenic pubertal process stimulates clitoral growth in these highly 'masculinized' hyaenas, parallel observations in females would be expected; however, the role of oestrogens in accounting for female-typical clitoral development would also have to be considered. The results of the present study suggest a limited role, if any for androgenic stimulation of phallic growth. That is, penile growth was greater during the 10 month period preceding puberty, than during an 18-month period that included the traditional increase in pubertal androgens. In addition, pre-pubertal castration had minimal effects on penile length, diameter, or the presence of penile spines. In females, most clitoral growth also occurred before puberty, although pre-pubertal ovariectomy produced significant reductions in clitoral diameter and the elasticity of the urogenital meatus. These feminine characteristics which normally distinguish the female from the male phallus in this species, were partially restored by a brief period of oestrogen administration. Both sexes displayed erections many years after pre-pubertal castration. The results of the present study suggest that postnatal phallic growth is largely independent of gonadal steroids, with oestrogenic facilitation of female-typical clitoral characteristics in spotted hyaenas.

Pattern and source of secretion of relaxin in the reproductive cycle of the spotted hyena (Crocuta crocuta).

Female spotted hyenas are highly masculinized at birth and have no external vagina. Copulation with males and birth of young are accomplished through the central urogenital canal of the clitoris. This unusual adaptation requires remarkable changes in the elasticity of the connective tissues of the clitoris, without which neither copulation nor birth would be possible. We hypothesized that relaxin, a hormone that increases the extensibility of the connective tissues of the uterus and cervix of many other mammalian species, plays a role in the clitoral changes observed in hyenas. Serum relaxin was determined by specific RIA. Relaxin was not detected in serum of males, pubertal or nonpregnant adult females, or ovariectomized females. Immunoactive relaxin was detected in serum of juveniles at the time of initial growth of the urogenital meatus. High concentrations of immunoactive relaxin appeared in the serum of pregnant hyenas in the 2 wk preceding parturition. Immunoassays of extracts of hyena tissues and serum obtained from uterine and ovarian veins indicated that the placenta was the predominant source of relaxin, with possible ovarian contributions. Circulating relaxin decreased promptly following cesarean section near term. We conclude that relaxin secretion coincides with changes in extensibility of clitoral connective tissues 1) during growth of the clitoris in juveniles and 2) near the time of parturition in adults.

Evolution of genital masculinization: why do female hyaenas have such a large 'penis'?

In place of a 'normal' external vagina, female spotted hyaenas bear a fully erectile, penis-sized clitoris through which they mate and give birth. Early hypotheses on the evolution of this organ have focused on its signal function, because the erect phallus is used by both sexes as part of submission or appeasement displays. However, a quite different hypothesis is suggested by recent data on the ecological function of female aggressiveness, and on the role of androgens in the development of aggressiveness and male genital development. In this view, the female phallus may have originated as an unselected side effect of selection for androgen-mediated bellicosity, a major advantage in the extraordinarily competitive hyaena social system.

Sexual dimorphism of perineal muscles and motoneurons in spotted hyenas.

Female spotted hyenas are known for their male-like genitalia, high levels of aggression, and dominance over males, characteristics which are attributed to exposure to elevated levels of testosterone in utero. Although the nervous system of spotted hyenas has not previously been examined, one might predict that neural systems which are sexually dimorphic in other mammals would be monomorphic in this species. Spinal motoneurons which innervate muscles associated with the phallus are located in Onuf's nucleus and are more numerous in males than in females in a wide array of mammals. Onuf's nucleus was examined in adult and neonatal spotted hyenas and, contrary to expectation, was found to be sexually dimorphic in the typical mammalian pattern: Males have significantly more motoneurons in Onuf's nucleus than do females. This dimorphism was correlated with a previously undescribed dimorphism in the relevant target musculature. Specifically, the morphology of the bulbocavernosus muscle is distinctly different in male and female spotted hyenas. Pregnant hyenas were treated with anti-androgen in an attempt to interfere with the actions of androgen during fetal development. Motoneuron number in Onuf's nucleus and the morphology of the bulbocavernosus muscle were feminized in males exposed to anti-androgen in utero.

Evidence of natural bluetongue virus infection among African carnivores.

Bluetongue is an International Office of Epizootics List A disease described as the century's most economically devastating affliction of sheep. Bluetongue (BLU) viruses were thought to infect only ruminants, shrews, and some rodents, but recently, inadvertent administration of BLU virus-contaminated vaccine resulted in mortality and abortion among domestic dogs. We present evidence of natural BLU virus infection among African carnivores that dramatically widens the spectrum of susceptible hosts. We hypothesize that such infection occurred after ingestion of meat and organs from BLU virus-infected prey species. The effect of BLU virus on endangered carnivores such as the cheetah and African wild dog requires urgent investigation. Also, the role of carnivores in the epizootiology of this disease needs elucidation.

A mechanism for virilization of female spotted hyenas in utero.

Female spotted hyenas exhibit male-like genitalia and dominance over males. Hyena ovarian tissues incubated in vitro produced large quantities of the steroid hormone precursor androstenedione. The activity of aromatase, which converts androstenedione to estrogen, was one-twentieth as great in hyena versus human placental homogenates. In comparison, the activity of 17 beta-hydroxysteroid dehydrogenase, which converts androstenedione to testosterone, was equal in the two homogenates. The limited aromatase activity may allow the hyena placenta to convert high circulating concentrations of androstenedione to testosterone, which results in virilization of the fetal external genitalia and possibly destruction of fetal ovarian follicles. Androstenedione production by residual ovarian stromal cells during reproductive life accounts for the epigenetic transmission of virilization in female spotted hyenas.

Hormonal correlates of 'masculinization' in female spotted hyaenas (Crocuta crocuta). 1. Infancy to sexual maturity.

This report is concerned with hormone concentrations accompanying sexual maturation in a highly 'masculinized' female mammal, the spotted hyaena, Crocuta crocuta. Plasma concentrations of testosterone, androstenedione and oestrogen were determined by radioimmunoassay in a longitudinal study of 12 female and eight male hyaenas 2.5-62.5 months old. Concentrations of testosterone were significantly higher in males than in females after 26.5 months of age, but earlier measurements did not differ between sexes. Mean testosterone concentrations in adult female hyaenas (0.4-0.5 ng ml-1) were similar to those in several other female mammals that do not display a 'masculine' profile, but mean concentrations of androstenedione (2.5-5.5 ng ml-1) in female hyaenas were significantly higher than in males (1.0-2.0 ng ml-1), at most ages. Oestrogen could not be detected (less than 0.03 ng ml-1) in females until about 14 months of age and then increased (to approximately 0.13 ng ml-1) between 18 and 30 months; oestrogen remained undetectable in males. This rise in oestrogen in females corresponded to nipple enlargement and to changes in the size and elasticity of the urogenital meatus, permitting copulation and parturition through the clitoris. Gonadectomy (two males and four females) at 4-7 months resulted in nondetectable concentrations of testosterone and oestrogen and a marked attenuation in androstenedione (to approximately 0.39 ng ml-1), indicating that the gonads are the major source of these three steroids. Gonadectomy also eliminated sex differences in weight, nipple development and elasticity of the urogenital meatus.

Hormonal correlates of 'masculinization' in female spotted hyaenas (Crocuta crocuta). 2. Maternal and fetal steroids.

Concentrations of androgens (androstenedione, testosterone, 5 alpha-dihydrotestosterone), oestrogen and progesterone were measured in relation to pregnancy in the spotted hyaena (Crocuta crocuta). The gestation period was estimated to be about 110 days. There was a marked progressive rise in all the steroids starting in the first third of gestation. Chromatographic separation of plasma showed that much of the oestrogen is not oestradiol (only 12% of total measured) and that a significant fraction of the 'testosterone' may be dihydrotestosterone. In the final third of pregnancy, concentrations of androgen (especially testosterone plus dihydrotestosterone) in the female circulation reached the maximal values of adult males; the percentage of dihydrotestosterone relative to total testosterone plus dihydrotestosterone was higher in females (44 +/- 3.9%, n = 20) than in males (29.5 +/- 3.5%, n = 17). Plasma androstenedione was also significantly higher in females, but the increment was less than for oestrogen, testosterone and progesterone, and the temporal pattern was less clear. Samples from the maternal uterine and ovarian circulation showed that androstenedione is largely of ovarian origin and metabolized by the placenta, while testosterone, progesterone and oestrogen are primarily of placental or uterine origin. Fetal samples were taken from two mixed-sex sets of twins and one male singleton. Gradients across the placenta measured in the fetal circulation confirmed that the placenta metabolizes androstenedione and is a source of testosterone for the female fetus; there were no consistent differences in androgens between male and female fetuses. It is suggested that the conspicuous masculinization of the female spotted hyaena, especially evident in the external genitalia at birth, is a result, at least in part, of high placental production of testosterone or dihydrotestosterone derived from the metabolism of high maternal androstenedione.

Fatal sibling aggression, precocial development, and androgens in neonatal spotted hyenas.

Fatal neonatal sibling aggression is common in predatory birds but has not been previously reported in wild mammals. Spotted hyena females are strongly masculinized, both anatomically and behaviorally, apparently by high levels of androgens during ontogeny. Neonates display elevated androgen levels, precocial motor development, and fully erupted front teeth. Litters are usually twins, and siblings fight violently at birth, apparently leading to the death of one sibling in same-sex litters, whereas in mixed-sex litters both siblings usually survive.

Scent marking (pasting) in a colony of immature spotted hyenas (Crocuta crocuta): a developmental study.

Pasting, a stereotypic form of anal gland scent marking, was studied in 2 cohorts (N = 20) of captive spotted hyenas (Crocuta crocuta). A significant increment in the frequency of pasting occurred in both cohorts as the animals approached sexual maturity; however, gonadectomy during the early juvenile age period had no significant effects on subsequent pasting frequency. Dominant hyenas in both cohorts tended to scent-mark more frequently than subordinates during the late subadult period. Pasting was facilitated by the immediately preceding pasting activities of other hyenas, as has been reported to occur in nature, and olfactory investigation was the most common behavior preceding pasting.

Routine application of the omental pedicle graft in 50 consecutive patients at risk for sternal wound infection.

After cardiac surgery, healing can be delayed by sternal wound infection, particularly if mediastinitis develops. Because of the technical simplicity of omentopexy, we recommend the use during open-heart surgery of an omental pedicle graft in selected cases to prevent postoperative complications. This article describes our experience over a 4-month period (from 30 March 1989 through 2 August 1989) with this technique in 50 consecutive patients at moderate-to-high risk for postoperative sternal and mediastinal problems. The patients included 39 men (78%) and 11 women (22%), whose ages ranged from 22 to 83 years (mean, 55 years). Preoperative risk factors included extreme obesity, 13 patients (26%); chronic obstructive pulmonary disease, 13 patients (26%); diabetes mellitus, 6 patients (12%); obesity and diabetes, 8 patients (16%); and obesity, diabetes, and chronic obstructive pulmonary disease, 3 patients (6%). Operative risk factors included cardiac reoperation involving prolonged surgery, 6 patients (12%); bilateral mammary grafting, 17 patients (34%); and the need for prolonged (greater than 72-hour) mechanical respiratory assistance, 2 patients (4%). Three of the 50 patients (6%) were considered to be at moderate risk due to an increase in nosocomial infections at the time of their surgical procedures. Although the omentopexy itself caused no complications, 5 patients had major complications related to the cardiac procedure. Two of these patients died, for an operative mortality of 4%; death was caused by progressive peritonitis in 1 case and by cardiac tamponade in the other case. At least 2 of the remaining 3 patients withstood localized mediastinal infection and had thereafter an extremely benign postoperative course. We conclude that an omental pedicle graft, placed prophylactically in patients at risk for sternal wound infection, can serve as a valuable adjunct to healing after cardiac surgery.

Sex differences in the play behavior of immature spotted hyenas, Crocuta crocuta.

Social, locomotor, and object play were studied in a colony of five male and five female peer-reared spotted hyenas during 12 1-hr tests while the animals were 13-19 months of age. Animals were tested in both same-sex and mixed-sex groups and were stimulated to play by the introduction of fresh straw and sawdust bedding. Each test was videotaped and the frequency of each type of play was determined by a time sampling procedure. Females played more frequently than males, however, the category of play which was elevated depended upon the social context during testing. In same-sex tests the frequency of vigorous social play displayed by females markedly exceeded that by males, but no comparable sex difference appeared in mixed-sex tests. Females engaged in locomotor play more frequently than males in mixed-sex tests, but no comparable sex difference appeared in same-sex tests. No sex difference in object play was observed. Two male and two female hyenas were gonadectomized prior to the initiation of the present sequence of tests. The results suggest that gonadectomy during the prepubertal period does not affect the frequency of play behavior. However, the small sample sizes preclude any conclusive determination of the effects of these gonadectomies on play.

Androstenedione may organize or activate sex-reversed traits in female spotted hyenas.

Spotted hyenas (Crocuta crocuta Erxleben) present a unique syndrome of reversal in behavioral and anatomical distinction between the sexes: females are heavier and more aggressive than males and dominant over them. The female's external genitalia include a false scrotum and a fully erectile pseudopenis through which mating and birth take place. Results of studies of circulating testosterone levels in wild spotted hyenas do not account for the "male-like" characteristics of the female. Androstenedione, however, is consistently higher in females than in males, particularly during early infancy. Experiments on rodents show that androstenedione can be a potent organizer of anatomical and behavioral differentiation. This study suggests that it may also produce the profound virilization of female spotted hyenas.