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

Relaxin as a hormonal aid to evaluate pregnancy and pregnancy loss in bottlenose dolphins (Tursiops truncatus)

This study was conducted to critically evaluate weekly and monthly circulating concentrations of immunoreactive relaxin throughout pregnancies that resulted in live births, stillbirths, and abortions in aquarium-based bottlenose dolphins. A relaxin RIA was used to analyze serum collected during 74 pregnancies involving 41 dolphins and 8 estrous cycles as well as 8 non-pregnant dolphins. Pregnancies resulted in live births (n=60), stillbirths (n=7), or abortions (n=7). Relative to parturition (Month 0), monthly changes (P<0.0001) in relaxin was indicated by relatively low concentrations during early pregnancy (Months -12 to -9) which subsequently increased (P<0.05) during mid- (Months -8 to -5) to late (Months -4 to -1) pregnancy; relaxin was highest (P<0.05) at the time of parturition. Post-parturition (Month 1), concentrations decreased (P<0.05). During the first 4weeks post-ovulation, relaxin concentrations were not different between pregnant and non-pregnant dolphins (status-by-week interaction, P=0.59). Status-by-month interaction (P<0.0002) involving different pregnancy outcomes was due, impart, to an increase in relaxin during early pregnancy (P<0.05) that was comparable among dolphins with live births, stillbirths, and abortions except concentrations were lower (P<0.05; 52%) at mid-pregnancy in association with pregnancy loss. Thereafter, concentrations increased (P<0.05) during late pregnancy in dolphins with stillbirths but not in dolphins with abortions. In conclusion, this study provided new information on the pregnancy-specific nature of relaxin, critical evaluation of the fundamental characteristics of relaxin during pregnancy and pregnancy loss, and clarification on the strengths and limitations of relaxin as a diagnostic aid to determine pregnancy status and assess maternal-fetal health in bottlenose dolphins.

Relaxin: a hormonal aid to diagnose pregnancy status in wild mammalian species

In the beginning of 1960s, seminal studies characterizing circulating concentrations of immunoreactive relaxin in companion dogs and evaluating the differences in concentrations among pregnant, nonpregnant, and pseudopregnant bitches indicated the potential for relaxin to be applied clinically as a diagnostic aid to detect pregnancy status in wild animal species. A brief historical overview of the nature of relaxin and early work to develop and validate immunologic methods to analyze relaxin in the blood of rodents and pigs is initially discussed, which is followed by a summary of the development and validation of relaxin immunoassays to diagnose pregnancy in companion dogs and cats. Thereafter, observation of the pregnancy-specific increase in circulating concentrations of relaxin in laboratory, companion, and farm animal species leads to discussion on the application of radioimmunoassays, enzyme immunoassays, and a rapid immunomigration assay to diagnose pregnancy in wild terrestrial (e.g., wolves, lions, elephants, rhinoceros, panda) and marine (e.g., seals, dolphins) mammal species. A reference table is included with a comprehensive list of numerous species and essential reagents that have been used in various in-house and commercial immunoassays to successfully analyze relaxin quantitatively and qualitatively in blood (serum or plasma) and to some extent in urine. Although the detection of relaxin concentrations has the potential to aid in the diagnosis of pregnancy in many wild animal species, there are challenges in other species. Future efforts should focus on validation of nonradiolabeled relaxin immunoassays for broader application among species and improving techniques (e.g., extraction, purification) to analyze relaxin in samples other than blood (e.g., urine, feces, saliva, blow, skin, blubber) that can be collected in a less-invasive or -stressful manner and processed accordingly for basic and applied purposes, especially with application toward conservation of threatened or endangered species.

Development of the external genitalia: perspectives from the spotted hyena (Crocuta crocuta)

This review/research paper summarizes data on development of the external genitalia of the spotted hyena, a fascinating mammal noted for extreme masculinization of the female external genitalia. The female spotted hyena is the only extant mammal that mates and gives birth through a pendulous penis-like clitoris. Our studies indicate that early formation of the phallus in both males and females is independent of androgens; indeed the phallus forms before the fetal testes or ovaries are capable of synthesizing androgens. Likewise, pre- and postnatal growth in length of the penis and clitoris is minimally affected by "androgen status". Nonetheless, several internal morphologies, as well as external surface features of the phallus, are androgen-dependent and thus account for dimorphism between the penis and clitoris. Finally, estrogens play a critical role in penile and clitoral development, specifying the position of the urethral orifice, determining elasticity of the urethral meatus, and facilitating epithelial-epithelial fusion events required for proper formation of the distal urethra/urogenital sinus and prepuce. Accordingly, prenatal inhibition of estrogen synthesis via administration of letrozole (an aromatase inhibitor) leads to malformations of the glans as well as the prepuce (hypospadias). The effects of prenatal androgens, anti-androgens and impaired estrogen synthesis correlated with the tissue expression of androgen and estrogen receptors.

Pregnancy diagnosis in wild canids using a commercially available relaxin assay

Accurate detection of pregnancy is a useful tool in zoo management and husbandry, conservation breeding programs and research settings. Our study evaluated the ability of a commercial relaxin hormone assay used in domestic dogs (ReproCHEK(TM)) to accurately detect pregnancy through plasma analysis in two wolf and two fox species. The relaxin assay detected all of the pregnancies greater than 25 days gestation for island foxes, fennec foxes, gray wolves, and Mexican gray wolves. For island foxes, three negative relaxin results were attributed to using the test earlier postconception than manufacturer recommendation (before day 20). Five other negative results were found for females estimated at 15-25 days gestation, spanning the early and intermediate period (21-30 days gestation) when relaxin may be detected but less reliably. There were no false-positive results in nonmated negative control animals. Relaxin assay results were highly correlated with ultrasound results and the intra-assay replicate agreement was 100%. Our results show that the ReproCHEK(TM) commercial relaxin assay is a minimally invasive and reliable method for pregnancy detection in these wild species when used after 25 days gestation and might be applied to other canids as well. Furthermore, this assay is easy to run and requires no specialized equipment, making it extremely useful for zoo and field research applications. Zoo Biol 27:406-413, 2008. (c) 2008 Wiley-Liss, Inc.

Relaxin and progesterone during pregnancy and the post-partum period in association with live and stillborn calves in bottlenose dolphins (Tursiops truncatus)

The objectives of this study were to validate a relaxin and progesterone RIA for use in bottlenose dolphins, and quantify and characterize both hormones in extracts of placental tissue and serum collected during pregnancy and the post-partum period, and compare the results between dolphins with live and stillborn calves. In Experiment 1, validation of a heterologous relaxin and progesterone RIA involved specific displacement of antibody-bound radiolabeled human relaxin or progesterone in response to increasing volumes of pooled pregnant dolphin serum and amounts of respective hormone standards added to a fixed volume of serum. The displacement curves were considered parallel and additive relative to respective standard curves. In Experiment 2, immunoreactive relaxin and progesterone were detected in placental extracts and, in corresponding serum samples, concentrations of both hormones were higher during the pre-partum than post-partum periods. Circulatory concentrations of progesterone decreased (P < 0.05) from relatively high concentrations during early and mid-pregnancy to intermediate concentrations by late pregnancy (month effect, P < 0.0001) in dolphins with live births, whereas, in dolphins with stillbirths, the decrease in progesterone began earlier (month-by-birth status interaction, P < 0.007); mean concentrations were lower at mid- (37%, P < 0.06) and late (25%) pregnancy. Temporally, relaxin increased (P < 0.05) progressively from relatively low concentrations during early pregnancy to high concentrations during late pregnancy (month effect, P < 0.0001) and was not different between birth statuses (birth status effect, P = 0.76; month-by-birth status interaction, P = 0.17). Even though the interaction did not reach significance, mean relaxin concentrations were 42%, 29%, and 34% lower at early, mid-, and late pregnancy, respectively, in dolphins with stillbirths than in those with live births. In conclusion, the pregnancy-specific increase in serum concentrations of relaxin and lower concentrations of both relaxin and progesterone in association with stillbirths suggest the potential for relaxin to be used diagnostically to determine pregnancy status, and one or both hormones to be used to assess placental function, and, perhaps, fetal well-being in bottlenose dolphins and other cetaceans.

Validation of a homologous canine relaxin radioimmunoassay and application with pregnant and non-pregnant Northern fur seals (Callorhinus ursinus)

The primary objectives of this study were to validate a canine relaxin RIA for use in otariids and phocids and consider practical applications. For 6 captive Northern fur seal females, serum samples were grouped and examined according to pregnancy (n=13), post-partum (n=8) and non-pregnancy (n=6), and, for 2 captive Northern fur seal males, serum samples were grouped and examined together regardless of age (2 mo-15 yrs, n=6). Placental tissue was available for examination from one Northern fur seal, Steller sea lion and harbor seal. The validation process involved several steps using an acid-acetone extraction process to isolate a relaxin-containing fraction in pools of serum from each group of fur seals and placental tissue from each seal species. A relaxin-like substance was detected in extracts of pregnant, non-pregnant and male serum and placental tissue in a dose-responsive manner as increasing volumes of respective extracts or amounts of canine relaxin were introduced into the assay. In raw serum samples, mean immuno-reactive relaxin concentrations were higher (P<0.05) during pregnancy than post-partum and non-pregnancy, and lower (P<0.05) in male than female fur seals. During pregnancy, mean serum concentrations of relaxin progressively increased (P<0.05) over Months 4-10 and, in serial samples collected from the same fur seals before and after parturition, mean concentrations were higher (P<0.06) pre-partum than post-partum. In conclusion, validation of a homologous canine relaxin RIA for use in otariids and phocids resulted in the discovery of a relaxin-like substance in extracted and raw serum and placental tissue from Northern fur seals, a Steller sea lion and harbor seal. Distinctly higher immuno-reactive concentrations during pregnancy indicated the potential for relaxin to serve as a hormonal marker to differentiate between pregnant and non-pregnant or pseudopregnant pinnipeds.

External genital morphology of the ring-tailed lemur (Lemur catta): females are naturally "masculinized"

The extravagance and diversity of external genitalia have been well characterized in male primates; however, much less is known about sex differences or variation in female form. Our study represents a departure from traditional investigations of primate reproductive anatomy because we 1) focus on external rather than internal genitalia, 2) measure both male and female structures, and 3) examine a strepsirrhine rather than an anthropoid primate. The subjects for morphological study were 21 reproductively intact, adult ring-tailed lemurs (Lemur catta), including 10 females and 11 males, two of which (one per sex) subsequently died of natural causes and also served as specimens for gross anatomical dissection. Male external genitalia presented a typical masculine configuration, with a complex distal penile morphology. In contrast, females were unusual among mammals, presenting an enlarged, pendulous external clitoris, tunneled by the urethra. Females had a shorter anogenital distance and a larger urethral meatus than did males, but organ diameter and circumference showed no sex differences. Dissection confirmed these characterizations. Noteworthy in the male were the presence of a "levator penis" muscle and discontinuity in the corpus spongiosum along the penile shaft; noteworthy in the female were an elongated clitoral shaft and glans clitoridis. The female urethra, while incorporated within the clitoral body, was not surrounded by erectile tissue, as we detected no corpus spongiosum. The os clitoridis was 43% the length and 24% the height of the os penis. On the basis of these first detailed descriptions of strepsirrhine external genitalia (for either sex), we characterize those of the female ring-tailed lemur as moderately "masculinized." Our results highlight certain morphological similarities and differences between ring-tailed lemurs and the most male-like of female mammals, the spotted hyena (Crocuta crocuta), and call attention to a potential hormonal mechanism of "masculinization" in female lemur development.

Mammalian sexual differentiation: lessons from the spotted hyena

Female spotted hyenas (Crocuta crocuta) are the only female mammals that lack an external vaginal opening. Mating and birth take place through a urogenital canal that exits at the tip of a hypertrophied clitoris. This 'masculine' phenotype spurred a search for an alternate source of fetal androgens. Although androstenedione from the maternal ovary is readily metabolized to testosterone by the hyena placenta, formation of the penile clitoris and scrotum appear to be largely androgen independent. However, secretions from the fetal testes underlie sex differences in the genitalia and central nervous system that are essential for male reproduction. Naturally circulating androgens, acting prenatally, reduce reproductive success in adult female spotted hyenas. Effects on aggression and dominance might offset these reproductive 'costs' of female androgenization in utero.

Sexual differentiation in three unconventional mammals: spotted hyenas, elephants and tammar wallabies

The present review explores sexual differentiation in three non-conventional species: the spotted hyena, the elephant and the tammar wallaby, selected because of the natural challenges they present for contemporary understanding of sexual differentiation. According to the prevailing view of mammalian sexual differentiation, originally proposed by Alfred Jost, secretion of androgen and anti-Mullerian hormone (AMH) by the fetal testes during critical stages of development accounts for the full range of sexually dimorphic urogenital traits observed at birth. Jost's concept was subsequently expanded to encompass sexual differentiation of the brain and behavior. Although the central focus of this review involves urogenital development, we assume that the novel mechanisms described in this article have potentially significant implications for sexual differentiation of brain and behavior, a transposition with precedent in the history of this field. Contrary to the "specific" requirements of Jost's formulation, female spotted hyenas and elephants initially develop male-type external genitalia prior to gonadal differentiation. In addition, the administration of anti-androgens to pregnant female spotted hyenas does not prevent the formation of a scrotum, pseudoscrotum, penis or penile clitoris in the offspring of treated females, although it is not yet clear whether the creation of masculine genitalia involves other steroids or whether there is a genetic mechanism bypassing a hormonal mediator. Wallabies, where sexual differentiation occurs in the pouch after birth, provide the most conclusive evidence for direct genetic control of sexual dimorphism, with the scrotum developing only in males and the pouch and mammary glands only in females, before differentiation of the gonads. The development of the pouch and mammary gland in females and the scrotum in males is controlled by genes on the X chromosome. In keeping with the "expanded" version of Jost's formulation, secretion of androgens by the fetal testes provides the best current account of a broad array of sex differences in reproductive morphology and endocrinology of the spotted hyena, and androgens are essential for development of the prostate and penis of the wallaby. But the essential circulating androgen in the male wallaby is 5alpha androstanediol, locally converted in target tissues to DHT, while in the pregnant female hyena, androstenedione, secreted by the maternal ovary, is converted by the placenta to testosterone (and estradiol) and transferred to the developing fetus. Testicular testosterone certainly seems to be responsible for the behavioral phenomenon of musth in male elephants. Both spotted hyenas and elephants display matrilineal social organization, and, in both species, female genital morphology requires feminine cooperation for successful copulation. We conclude that not all aspects of sexual differentiation have been delegated to testicular hormones in these mammals. In addition, we suggest that research on urogenital development in these non-traditional species directs attention to processes that may well be operating during the sexual differentiation of morphology and behavior in more common laboratory mammals, albeit in less dramatic fashion.

Urogenital system of the spotted hyena (Crocuta crocuta Erxleben): a functional histological study

The unique urogenital anatomy and histology of female spotted hyenas (Crocuta crocuta Erxleben) was reexamined to identify adaptations of "structure" that enable/facilitate urination, mating, and parturition through the clitoris. Unusual features of penile anatomy required for meeting ceremonies and successful mating through a clitoral point of insertion were also examined. As reported previously, the upper urogenital tract of the female spotted hyena is typical of other carnivores and consists of the oviducts, uterine horns, uterine body, and vagina. An anatomically defined cervix is absent, even though a histologically defined transition zone between the uterine body and vagina was demonstrated. Adaptive features of the upper genital tract were a helical-shaped uterine cavity, extensive smooth muscle in the uterus and vagina, and a newly discovered submucosal mucous urogenital gland (SMUG) located immediately caudal to the vagina. The extensive smooth muscle facilitates the expulsion of the large pups at parturition through the recurved birth canal. Secretions of the SMUG provide lubrication and protection for the urogenital mucosa during mating and parturition. Two types of "erections" are suggested by behavioral observations: the common hemodynamic erection required for insertion and thrusting by the male, and phallic "flipping" that commonly occurs earlier in the mating sequence and is sometimes seen during meeting ceremonies. Phallic "flipping" appears to be accomplished by the coordinated contractions of the large ischiocavernosus and retractor muscles acting on the semirigid organ. The extremely thick tunica albuginea and interstitial collagen of the common corporal body of the penis and clitoris gives the flaccid phallus some degree of rigidity even in the resting state in males and nulliparous females. Phallic "flipping" implies a hinge region in which flexibility is the key feature. Such a proximal hinge region of the male and female phallus was defined and was notable for its diminished collagen content. The urogenital sinus traversing the clitoris was specialized for distensibility, thus facilitating receipt of the penis during mating and for passage of the infant to the tip of the glans clitoris, where it emerges at parturition. The morphology of the glans penis is notable for the tapered common corporal body that extends to the distal tip of the glans. This adaptation is suggested to be required for a clitoral (as opposed to a vaginal) point of insertion during mating. Finally, additional segments of erectile tissue devoid of a thick collagenous capsule were demonstrated in the glans penis and glans clitoris, which appear to account for the "partially-locking" of the male into the female during the late stages of a mating sequence. Taken together, it is evident that the unusual sexual behaviors of the male and female spotted hyenas are facilitated by unique structural modifications of the relevant organs.

The story of the spotted hyena and the hermaphrodite: biological order and enigma

The complex problem of genital masculinization is illustrated in this article from the perspectives of comparative zoology, and pediatric plastic surgery on intersex children. In addition, criticism and recommendations coming from patient internet communications are introduced into the medical community.