Comparative ovarian function and reproductive monitoring of endangered mammals

Development of a 3D in vitro model to study corpus luteum of felids based on luteinized cells from antral follicles

The study aimed to establish a long-term 3D cell culture model using luteinized follicular cells to investigate the functionality and life cycle of the CL in felids. A mixture of cell types from antral follicles was luteinized in vitro and cultured for up to 23 days. The method, initially applied to the domestic cat, was later extended to Persian and Clouded leopards. Antral follicles were isolated and digested with enzymes; then, the cells were subjected to culture. Experimental subsets were treated with/without 1 µg/mL cloprostenol to validate the cell culture model's suitability for functional studies. In domestic cat samples, microscopic evaluation indicated luteinization, which was confirmed by increased progestagen concentrations and IHC staining for HSD3B and CYP11A1. The gene expression of selected steroidogenic factors (HSD3B1, STAR, CYP11A1) and hormone receptors (LHCGR, PTGFR, PRLR) significantly increased, while CYP17A1 expression decreased. Cloprostenol treatment resulted in reduction of steroidogenic activity, proving its suitability for functional studies. Persian and Clouded leopards' cell cultures exhibited similar patterns in progestagen secretion and gene expression, compared to domestic cats. This model, with its defined luteinization, as well as high and stable progestagen production, allows future investigation of factors regulating CL life cycle and function.

Validating enzyme immunoassays for non-invasive reproductive hormone monitoring in Temminck's pangolin

Gonadal hormones play a central role in reproductive function and success. As such, quantifying reproductive hormones non-invasively in threatened, vulnerable and endangered wildlife species offers an ideal tool for assessing general and individual reproductive patterns in situ. Whilst the use of faeces as a hormone matrix is often preferred in these cases, the required enzyme immunoassays (EIAs) for measuring faecal androgen (fAM), oestrogen (fEM) and progestagen metabolite (fPM) concentrations must first be validated if a species gets investigated for the first time to ensure biologically relevant patterns can be observed. In this study we aimed to biologically validate the EIAs for monitoring fAM, fEM and fPM concentrations in Temminck's pangolin, Smutsia temminckii. Hormone metabolite concentrations derived from each EIA tested were compared between different age and sex classes. An epiandrosterone EIA effectively measured androgen levels in males, distinguishing between adult and juvenile individuals, as well as both female age classes. Similarly, the tested oestrogen EIA successfully distinguished between adult and juvenile female fEM concentrations, and both tested progestagen EIAs demonstrated adequate differences between fPM concentrations of adult and juvenile females. The now-validated EIAs offer robust tools for a non-invasive monitoring of reproductive activity in Temminck's pangolin. The development of such techniques will allow researchers to assess reproductive hormone patterns of the species in situ, whilst also paving the way for further studies in this field. Despite the small sample size due to the species' conservation status, the study provides a foundation for future research using a robust, validated, non-invasive monitoring tool. The latter can now be implemented in long-term monitoring with larger sample sizes to yield more comprehensive data, aiding in the conservation of Temminck's pangolin.

Monitoring egg fertility, embryonic morbidity, and mortality in an oviparous elasmobranch using ultrasonography

Ultrasonography is widely used to monitor pregnancy in viviparous species, but it is underutilized as a tool to characterize embryonic development in oviparous species. Currently, a multi-institutional effort is underway to re-wild the endangered zebra shark (Stegostoma tigrinum) to locations where this species was previously extirpated by leveraging the reproductive efforts of aquarium sharks as a source of brood stock. Zebra sharks are oviparous and fecund, but a large percentage of their yolked eggs do not result in hatchlings. Therefore, ultrasonography represents a potential tool for distinguishing fertile eggs with developing embryos from degrading eggs, and to diagnose changes in early embryonic development predictive of poor outcomes. The objectives of the current study were to use ultrasonography to assess egg fertility, monitor early embryonic development, and identify morphological indicators that may be predictive of early embryonic mortality. Freshly laid eggs from four female zebra sharks were collected and inventoried daily at Aquarium of the Pacific. Eggs were incubated undisturbed for 2 to 4 weeks and subsequently examined weekly via ultrasound to assess fertility and monitor embryo development. Among 120 fertile eggs, embryos were identified as early as 8 days post-oviposition, with average (±SD) time to first observation at 30 ± 7 days. Morphological and behavioral abnormalities were observed for most embryos (n = 84, 70%) as early as 16 days and up to 95 days post-oviposition. Common abnormalities included: bent or curled tails, vesicle(s) at the base of the yolk stalk, and slow or weak movement. Only one embryo survived to hatch during the study and was genetically-confirmed parthenogenetic, suggesting hatching success for parthenotes is low (<1%). Ultrasonography was demonstrated to be an effective and non-invasive method to determine egg fertility, identify embryos with developmental abnormalities, and monitor embryo growth.

Prolonged cold-preservation of domestic cat ovarian tissue is improved by extracellular solution but impaired by the fragmentation of ovary

For domestic cats ovaries, recommended cold-storage limit is 24 h in Phosphate Buffered Saline (PBS) or Dulbecco`s PBS (DPBS). Here, we attempted to verify wheatear cat ovaries may benefit from more complex solutions during prolonged cold-storage (>24 h). First, the preservation capabilities of extracellular (SP+), intracellular (UW) solutions and DPBS supplemented with glutathione (DPBS+GSH) were compared using ovary fragments from the same ovary (n=10). Intact ovary stored in DPBS served as a control. Ovaries were kept at 4 °C for 48 h, and 72 h. In the second experiment, first ovary was stored in DPBS, second in SP+ or UW solution for 48 h (n = 12). Ovaries pairs stored in DPBS for 24 h served as a control (n=8). Tissue samples were evaluated directly after cold-storage and after following 24 h in vitro culture. Ovarian follicle morphology, apoptosis rates (cleaved caspase-3, TUNEL), and follicular growth activation (Ki-67) were assessed. Ovary fragmentation impaired follicular morphology preservation upon cold-storage comparing to intact ovary. However, ovarian fragments stored in UW for 48 h and in SP+ for 72 h presented better morphology than DPBS+GSH group. Comparison of intact ovaries cold-storage for 48 h showed that SP+ provided superior follicular morphology over DPBS, and it was comparable to the outcome of 24-hour storage. No follicular activation after in vitro culture was observed. Nevertheless, tissue culture increased considerably caspase-3 cleavage and TUNEL detection. The ovary fragmentation prior to cold-storage is not recommended in domestic cats. Replacement of DPBS with SP+ solution for whole ovary and UW solution for ovarian tissue fragments improves follicular structure preservation during 48-hour cold-storage.

Scent detection dogs as a novel method for oestrus detection in an endangered species, the Tasmanian devil (Sarcophilus harrisii)

Captive breeding is a critical tool for conservation of endangered species. Identifying the correct time to pair males and females can be a major challenge for captive breeding programmes, with current methods often being invasive or slow. Detection dogs may provide a non-invasive way to determine female receptivity, but this has not been explored in captive wildlife. This exploratory study investigated the use of detection dogs as a novel method of oestrus detection in the endangered Tasmanian devil (Sarcophilus harrisii). Faecal samples were collected from 11 captive female devils during the breeding seasons of 2020 and 2021. Three dogs with prior detection experience were trained and subsequently assessed (n = 188 searches per dog), on their ability to discriminate between oestrus and non-oestrus devil faecal samples, in a one sample set-up. When assessed on training samples, dogs were able to correctly discriminate oestrus from non-oestrus with a mean sensitivity of 69.1% and mean specificity of 65.7%. When assessed on novel samples, their sensitivity to oestrus dropped (mean sensitivity of 48.6%). However, they were still able to correctly identify non-oestrus samples (mean specificity of 68.1%). This study is the first to explore detection dogs' ability to identify oestrus in a captive breeding programme for endangered wildlife, providing a promising tool for non-invasive monitoring of reproductive status in wildlife.

Non-invasive Assessment of Fecal Glucocorticoid and Androgen Metabolites in the Pygmy Hippopotamus (Choeropsis liberiensis)

The pygmy hippopotamus (Choeropsis liberiensis) is an endangered species endemic to the Upper Guinea Forest ecosystem in West Africa. We have limited information concerning the species' reproduction and well-being under managed care. We therefore developed non-invasive methods for characterizing gonadal androgen and adrenal hormone profiles in pygmy hippos using fecal samples collected from 12 males and 12 females housed in North American zoological institutions. We aimed to: 1) identify and validate enzyme immunoassays (EIAs) for measuring metabolites of corticosteroids and testosterone in feces; and 2) test whether gonadal activity is correlated with previous breeding history, season or type of housing. For glucocorticoids, several EIAs for measuring metabolites were investigated. A group-specific EIA exhibiting cross-reactivity with 11,17-dioxoandrostane (DOA) metabolites of cortisol most clearly reflected adrenocortical activity in response to ACTH¹ challenge in both males and females. However, day-to-day concentrations of this metabolite in the feces of pygmy hippos that did not undergo ACTH challenge were near the detection limits of the assay, making this EIA impractical for assessing glucocorticoid activity in this species. Another group-specific EIA, exhibiting cross-reactivity with 5α-pregnane-3β,11β,21-triol-20-one, produced biologically relevant data and evidence of an appropriate response to pharmacological challenge with exogenous ACTH. The testosterone metabolite assay C196 (Arbor Assays, Ann Arbor, Michigan, USA) also produced biologically coherent data: adult males exhibited the highest mean androgen metabolite concentrations (477 ng/g), followed by adult females (259 ng/g) and juvenile males (160 ng/g). Proven breeding males had higher, but not significantly different, mean concentrations (472 ng/g) to unproven males (352 ng/g; P = 0.400). Similarly, adult males housed outdoors year-round in subtropical climates exhibited higher, but not statistically different mean concentrations (554 ng/g) to males in temperate climates that were housed indoors at least part of the year (412 ng/g; P = 0.208). There were, however, significant differences in mean concentrations among seasons for adult males, with higher values in spring (546 ng/g) and summer (542 ng/g) than in autumn (426 ng/g) and winter (388 ng/g, P = 0.003). In conclusion, we identified EIAs for the measurement of fecal metabolites of androgens and glucocorticoids that can be used for further studies to monitor gonadal activity in male pygmy hippos and adrenocortical activity in both sexes. We also identified a seasonal trend in male gonadal activity in this species under managed care in North America. Finally, our findings highlight an important consideration when using non-invasive methods for evaluating fecal cortisol metabolites: ACTH used for pharmacological validation of an EIA does not necessarily equate to biological relevance.

Linking socio-sexual and vocal behaviour with faecal progesterone and oestrogen metabolite levels in Southern white rhinoceros females

Progesterone and oestrogen are the main gonadal steroid hormones that regulate the ovarian activity and induce the fertile oestrus period in females. The monitoring of this receptive phase is particularly decisive for captive breeding and is commonly based on the observation of female behavioural patterns that coincide with their hormonal oestrus. However, in the white rhinoceros (WR), a species that is well known for its impaired reproductive rate in captivity, the female behavioural and vocal indicators of receptivity have not been systematically investigated or linked to their hormonal states so far. In order to close this gap, we combined behavioural and acoustic recordings, conducted over an average period of 32 days, with the analysis of faecal progesterone and oestrogen metabolite concentrations (fPM and fEM) in 27 adult Southern white rhinoceros (Ceratotherium simum simum; SWR) females from 10 European zoos. For eight of the study females, we were able to detect a receptive period indicated by their acceptance of sexual behaviour from the bulls. The comparison of behaviour and vocalization between receptive and non-receptive periods in these females demonstrated that particularly presenting and marking behaviour distinctly peaked during the receptive period, indicating the significance of olfactory signalling for female reproductive behaviour. Based on the analysis of fPM profiles, we were able to identify different reproductive states (cycling, non-cycling, pregnant) in 21 of 27 study females. In contrast, fEM profiles proved to be unsuitable for the detection of ovarian activity. For the majority (five of six females for which behavioural receptivity and endocrine cyclicity were determined), a coincidence of their receptive period and the hormonal oestrus, indicated by a nadir in fPM levels, could be detected. Conclusively, this study revealed a comprehensive behavioural repertoire that reflects the hormonal oestrus in SWR females and can therefore be reliably used for non-invasive ex situ reproduction monitoring.

Use of a simplified non-invasive technic to monitor fecal progesterone metabolites and reproduction function in several zoo species: Efficacy of mini VIDAS® automate (bioMérieux)

Developing the zoos' ability to assess the reproductive status of the individuals they house is essential to improve the husbandry and management of these species. The use of non-invasive techniques such as fecal hormone analysis has been proven to be a simple and effective way to achieve this. Designed by bioMérieux, mini VIDAS® instrument is used in human and veterinary medicine to evaluate different endocrinological parameters, including serum or plasma progesterone. This study evaluates VIDAS® Progesterone (PRG) assay's efficacy to monitor fecal progestagens using a simple sample extraction protocol adapted to the zoo environment. We compared (1) VIDAS® PRG fecal profiles with established assays specifically designed for fecal progestagens analysis at the VetmedUni (Vienna, Austria) for okapis (Okapia johnstoni), greater one-horned rhinoceros (Rhinoceros unicornis), giraffes (Giraffa camelopardalis reticulata) and hippopotamus (Hippopotamus amphibius) (2) VIDAS® PRG fecal profiles with VIDAS® PRG serum profiles for African elephants (Loxodonta Africana), giant anteater (Myrmecophaga tridactyla) and white rhinoceros (Ceratotherium simum). Spearman mean correlations were: 0.6748 for African elephants (n = 2 animals), 0.7969 for giant anteater (n = 1 animal), 0.7926 for okapis (n = 2 animals), 0.6072 for greater one-horned rhinoceros (n = 4 animals), 0.6062 for giraffes (n = 4 animals) and 0.5740 for hippopotamus (n = 2 animals). Fecal progestagens analysis revealed estrous cycles in several species: 12.5 ± 0.5 weeks for African elephants (n = 2 cycles), 15.3 ± 1.1 days for okapis (n = 6 cycles), 44 ± 2.1 days for greater one-horned rhinoceros (n = 4 cycles) and 15.5 ± 0.5 days for giraffes (n = 4 cycles). We observed pregnancies in a giant anteater, an okapi and a hippopotamus. We observed a strong positive Spearman correlation (r > 0.60) for individuals exhibiting estrous cycles. These first results indicate that the mini VIDAS® can be used for monitoring of the reproductive status of non-domesticated species and can be a useful tool for the reproductive management through fecal progesterone analysis. A simple extraction protocol was suitable for sample preparation of fecal progesterone metabolite analysis. Further studies using a larger number of individuals per species at different reproductive stages could confirm the relevance of mini VIDAS® in the zoo community.

Recent Progress in Spermatology Contributing to the Knowledge and Conservation of Rare and Endangered Species

There is a remarkable diversity in the animal kingdom regarding mechanisms underlying the production, maturation, structure, and function of sperm cells. Spermatology studies contribute to the knowledge of species diversity and also provide information about individual or population fitness. Furthermore, this fundamental research is required before collected spermatozoa can be used for conservation breeding, including assisted reproduction and cryobanking. This article aims to (a) review the most recent knowledge on sperm morphology and function in wild animal species, (b) analyze how this knowledge can be used to save species in their natural habitat or ex situ, and (c) propose future scientific directions in wildlife spermatology that could positively impact animal conservation. Variations in sperm structure and performance within and between species have multiple origins and significance. This collective body of knowledge enables the design and implementation of conservation strategies and action plans that integrate several disciplines. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 10 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Multi-year progesterone profiles during pregnancy in baleen of humpback whales (Megaptera novaeangliae)

Understanding calving rates of wild whale populations is critically important for management and conservation. Reproduction of humpback whales (Megaptera novaeangliae) is difficult to monitor and, even with long-term sighting studies, basic physiological information such as pregnancy rates and calving intervals remain poorly understood in many populations. We hypothesized that pregnant whales have sustained elevations in baleen progesterone that temporally correlate with gestation. To test this hypothesis, baleen progesterone profiles from two adult female North Pacific humpbacks, both with extensive sighting records and documented pregnancies, were compared to those of a nulliparous female (adult female never seen with a calf) and a juvenile male. Baleen specimens recovered during necropsy were subsampled every 2 cm from the base to the tip of the plate, with each interval representing 30-45 days of growth. Homogenized baleen powder was assayed for progesterone using enzyme immunoassays. The date of growth of each sampling location on the baleen plate was estimated based on stable isotope analysis of annual δ¹⁵N cycles. Progesterone profiles from both pregnant whales showed sustained high progesterone content (>350 ng/g) in areas corresponding to known pregnancies, inferred from calf sightings and post-mortem data. The younger female, estimated to be 13 years old, had higher progesterone during pregnancy than the 44.5 year old, but levels during non-pregnancy were similar. The nulliparous female and the male had low progesterone throughout their baleen plates. Baleen hormone analysis can determine how progesterone concentrations change throughout gestation and has potential for estimating age at first reproduction, pregnancy intervals, failed pregnancies and early calf mortality. Understanding rates of calving and current and historic reproductive patterns in humpbacks is vital to continuing conservation measures in this species.

Luteinizing Hormone Effect on Luteal Cells Is Dependent on the Corpus Luteum Stage in Felids

Simple Summary

The corpus luteum is a transient endocrine gland on the mammalian ovary, and its main function is to produce progesterone. Knowledge about the corpus luteum in felids is very limited and luteolytic and luteotrophic factors which regulate its maintenance and regression are not extensively studied. Information about corpus luteum function is needed to understand breeding strategies and to successfully implement assisted reproductive techniques for felids, of which most of the species are threatened. The aim of this study was to reveal the effect of luteinizing hormone on cultured luteal cells from corpora lutea obtained from selected felids and to investigate the protein expression of steroidogenic enzyme 3β-hydroxysteroid dehydrogenase by immunohistology.

Abstract

The objective of this study was to investigate the effect of luteinizing hormone (LH) on steroidogenic luteal cells obtained from corpora lutea (CL) of the domestic cat and selected wild felids. Luteal cells were isolated enzymatically from CL at different developmental stages and cultured for two days in the presence and absence of 100 ng/mL LH, respectively. Functionality was assessed by progesterone (P4) accumulation in cell culture media determined by ELISA. In addition, steroidogenic function was confirmed using immunohistochemistry for 3β-hydroxysteroid dehydrogenase (HSD3B). The enzymatic method allowed for the isolation of mostly small luteal cells in all investigated felids. Treatment with LH resulted in an increase in P4 secretion of cultured luteal cells obtained from CL in the formation stage (African lion) and development/maintenance stage (domestic cat (p < 0.05), Javan leopard), whereas luteal cells from more advanced stages of luteal development (regression) responded moderately or not at all to LH stimulation (domestic cat, Asiatic golden cat, Asiatic lion). The protein signal for HSD3B on CL was visible until development/maintenance. In conclusion, this study shows that LH promotes P4 production in luteal cells only until the onset of regression, when morphological signs are visible on the CL of felids and HSD3B is no longer detectable.

Endometrial receptivity and embryo implantation in carnivores-commonalities and differences with other mammalian species

Endometrial receptivity and embryo implantation processes are a major point of pregnancy failure in many mammalian species, including humans. Although reproductive biology in many carnivore species remains enigmatic, the few that have been studied so far are invaluable comparative models. The goals of this review are to (1) summarize current data on the mechanisms involved in uterine receptivity and embryo implantation in carnivores, including commonalities and differences with other mammalian species and (2) identify research priorities to better understand a key phenomenon in a critical group of mammals. Besides unique reproductive traits in some carnivores (induced vs. spontaneous ovulation in cats, ovulation at the germinal vesicle stage in dogs), preimplantation embryo development is comparable with other orders. However, the timing of implantation varies, especially in species having an embryonic diapause. Mechanisms involved in endometrial receptivity and decidualization still remain to be fully understood, but specific markers have already been identified. Importantly, the use of endogenous hormones to control the ovarian activity may impact endometrial receptivity and subsequent embryo implantation. Next, research efforts should take advantage of advanced technologies to further study embryo implantation in carnivores and to provide more relevant models to reproductive medicine or for the conservation of rare and endangered species.

Understanding and Assisting Reproduction in Wildlife Species Using Microfluidics

Conservation breeding and assisted reproductive technologies (ARTs) are invaluable tools to save wild animal species that are on the brink of extinction. Microfluidic devices recently developed for human or domestic animal reproductive medicine could significantly help to increase knowledge about fertility and contribute to the success of ART in wildlife. Some of these microfluidic tools could be applied to wild species, but dedicated efforts will be necessary to meet specific needs in animal conservation; for example, they need to be cost-effective, applicable to multiple species, and field-friendly. Microfluidics represents only one powerful technology in a complex toolbox and must be integrated with other approaches to be impactful in managing wildlife reproduction.

Breakthroughs and new horizons in reproductive biology of rare and endangered animal species

Because of higher extinction rates due to human and natural factors, more basic and applied research in reproductive biology is required to preserve wild species and design proper strategies leading to sustainable populations. The objective of the review is to highlight recent, inspiring breakthroughs in wildlife reproduction science that will set directions for future research and lead to more successes in conservation biology. Despite new tools and approaches allowing a better and faster understanding of key mechanisms, we still know little about reproduction in endangered species. Recently, the most striking advances have been obtained in nonmammalian species (fish, birds, amphibians, or corals) with the development of alternative solutions to preserve fertility or new information about parental nutritional influence on embryo development. A novel way has also been explored to consider the impact of environmental changes on reproduction-the allostatic load-in a vast array of species (from primates to fish). On the horizon, genomic tools are expected to considerably change the way we study wildlife reproduction and develop a concept of "precision conservation breeding." When basic studies in organismal physiology are conducted in parallel, new approaches using stem cells to create artificial gametes and gonads, innovations in germplasm storage, and more research on reproductive microbiomes will help to make a difference. Lastly, multiple challenges (for instance, poor integration of new tools in conservation programs, limited access to study animals, or few publication options) will have to be addressed if we want reproductive biology to positively impact conservation of biodiversity.

Assisted reproductive technologies for endangered species conservation: developing sophisticated protocols with limited access to animals with unique reproductive mechanisms

Assisted reproductive technologies (ARTs) have been proposed as a means of overcoming the significant challenges of managing small, isolated populations of endangered species in zoos. However, efficient protocols for ARTs do not exist for most endangered species. This review will focus on research efforts to characterize unique reproductive mechanisms and develop species-specific ARTs. Central to these studies are assays to measure steroid metabolites in urine or feces and/or training programs to allow unrestrained blood collections and ultrasound evaluations. The resulting information about estrous cycle dynamics, combined with studies of semen collection and processing, provides the foundation for the development of artificial insemination (AI). In vitro fertilization and embryo transfer are also discussed in relation to the advantages these techniques could provide relative to AI, as well as the significant challenges involved with technologies that require oocytes and embryos. Finally, an argument is made for additional research of nontraditional model species (e.g., domestic cats and dogs) and the development of novel models representing unique taxa. Whether these species are studied by zoo-based researchers with the expressed intent of developing ARTs for conservation or academic scientists interested in basic biology, the resulting information will provide a unique, evolutionary perspective on reproduction that could have wide-reaching benefits. The more information we have available, the better our chances will be of developing effective ARTs and making a difference in conservation efforts for endangered species.

First assessment of hoary fox (Lycalopex vetulus) seasonal ovarian cyclicity by non-invasive hormonal monitoring technique

Reproduction is key to species survival, and reproductive physiology represents a high priority investigative area for conservation biology, as it provides a basic understanding of critical life-history traits, information that is helpful for the establishment of management strategies. Here, we generated knowledge about the reproductive endocrinology of the hoary fox (Lycalopex vetulus), a small canid (2.5-4 kg) endemic to open areas of the Brazilian Cerrado and listed in the Brazilian National List of Endangered species. Specifically, we utilized non-invasive hormone monitoring methods to assess oestrogen and progestagen metabolites from eight female hoary foxes housed in five zoological institutions in the state of São Paulo-Brazil. We observed the elevations of oestrogen and progestagen metabolites between July and September in six of the eight females. No significant evidence of ovarian activity was observed during other months. Two females, who shared the same enclosure, did not show a pattern of reproductive cyclicity. Based on these characteristics, we concluded that captive hoary foxes are seasonal monoestric, with the beginning of the oestrus cycle occurring mainly in July followed by 2 months of the luteal phase when conception does not occur. We suggest the dosage of faecal metabolites of estradiol and progesterone could be used to differentiate the reproductive period from a non-reproductive period in Lycalopex vetulus females, providing relevant information about their reproductive biology that may contribute to species conservation and management strategies, such as increased ex situ reproductive success.

Equilibration in freezing extender alters in vitro sperm-oviduct binding in the domestic cat (Felis catus)

For the preservation of endangered felid species, epididymal sperm may be received from valuable individuals after castration or death and they need to be cryopreserved for storage. However, pregnancy rates with epididymal or cryopreserved sperm are lower than with ejaculated and non-frozen semen even if insemination is surgically performed into the oviduct. To investigate whether equilibration, the first step of the cryopreservation procedure, has an impact on sperm-oviduct binding, we generated oviduct epithelial cell vesicles from isthmus segments of preovulatory domestic cats. Binding assays were performed with epididymal sperm in a cell culture medium (M199) without supplements, or after cooling to 15 °C in a freezing extender (TestG), supplemented with glycerol and the water-soluble fraction of hen's egg yolk mainly comprising LDL. The sperm-oviduct binding was assessed both quantitatively and qualitatively (head or tail binding of sperm with active or inactive mitochondria). Most of the bound sperm prepared in M199 had active mitochondria and were attached to the vesicles by their heads. In equilibrated samples, the proportion of bound sperm with active mitochondria and the proportion of head-bound spermatozoa were reduced. The total motility of the sperm after 1 h of incubation in the absence or presence of vesicles were also affected by the preparation (higher in equilibrated) and the incubation (lower in co-incubated), while mitochondrial activity was influenced just by the preparation. Obviously, LDL has a beneficial effect on sperm motility, but we suggest that it interferes with the molecular sperm-oviduct crosstalk and causes a reduced binding of "good" sperm.

Reproductive biology and biotechnologies in wild felids

Conservation strategies in natural habitats as well as in breeding centers are necessary for maintaining and reinforcing viable populations of wild felids. Among the fundamental knowledge that is required for conservation breeding, a solid understanding of reproductive biology is critical for improving natural breeding and enhance genetic diversity. Additionally, it offers the opportunity to develop assisted reproductive technologies (ARTs) in threatened and endangered species. Conservation breeding and reproductive biotechnologies of wild felids have advanced in the past decade. It has been clearly shown that female felids have species and individual patterns of reproductive cycles and respond differently to exogenous hormones. In males, several species still have poor semen quality often due to the loss of genetic diversity in small populations. To overcome the challenges of natural breeding (incompatibility between individuals or suboptimal environment) and mitigate inbreeding, artificial insemination, embryo production and embryo transfer have been further developed in 24 wild cat species. Major factors limiting ART success are inconsistent responses to ovarian stimulation, variable quality of gametes and embryos, and preparation of recipient females. Additional approaches including stem cell technologies have been explored for future medical applications. However, there still is a critical need for better knowledge of feline reproductive biology and improvement of ARTs efficiency to increase the genetic diversity and create sustainable populations of wild felids.

Can jaguar (Panthera onca) ovulate without copulation?

Threatened of extinction in Brazil, the jaguar is the largest predator in Latin America, playing an important role in the ecosystem where it is inserted. Despite of some important studies in this species, its reproductive physiology needs to be better understood for the development of more effective reproductive biotechnologies. One well studied biological aspect is the occurrence of ovulation following stimulation of the vaginal floor during copulation. This mechanical stimulation is responsible for the induction of ovulation in domestic and wild cats. Thus, the objective of the present study was to evaluate whether ovulation in captive jaguars can be induced by the above-mentioned mechanical stimulation but also by other forms of sensory stimulation. Nine jaguar (Panthera onca) females and six males were divided into three groups: Group 1 (four females), in which the females were close to the males, but with no possibility of copulation; Group 2 (three females), in which the females were in the same enclosure as the males, thereby being able to copulate; and Group 3 (two females), in which the females were completely isolated from any male of the species. Follicular growth was stimulated by administration of 800 IU of eCG, conducted three or five days before LOPU. In order to have certainty about the occurrence of ovulation, the ovaries were assessed by laparoscopy allowing the visualization of ovarian structures including follicles, recent ovulations, corpora hemorrhagica (CH) and corpora lutea (CL). Multiple CH were observed in the 2 females housed with males, as well as the two females kept in proximity of males, i.e. only visual contact (Group 1). None of the females in complete isolation from males showed CH or ovulation spots (Group 3). In summary, the seven females in contact or near proximity with males had multiple ovulations, regardless of copulation or not. Based on this evidence, we have established that jaguars are capable of two forms of induced ovulation: 1) the "mechanical" coitus-induced form that is traditional and thoroughly described for felines; 2) a "sensorial" form in which the nearby presence of a male can induce ovulation through the visual, olfactory and/or auditive senses. Further research is required for establishing the mechanisms and chemical mediators of sensorial stimulation. In addition, and consistent with expected results, we confirmed that females that received the same stimulation are incapable of ovulating when not exposed to any form of stimulation by males.

Managed wildlife breeding-an undervalued conservation tool?

Knowledge of and the technologies and resources applied to the ex situ care for wildlife have improved greatly in recent years. This has resulted in numerous successes bringing back populations from the brink of extinction by the reintroduction or restoration of animals from conservation breeding programmes. Controlled breeding of wildlife by humans is discussed controversially in society and in scientific circles and it faces a number of significant challenges. When natural breeding fails, Assisted Reproduction Technologies (ART) have been postulated to increase reproductive output and maintain genetic diversity. Furthermore, technical advances have improved the potential for successful collection and cryopreservation of gametes and embryos in many wildlife species. With the aim of creating a better understanding of why ex situ and in situ conservation of threatened species must complement each other, and under which circumstances ART provide additional tools in the rescue of a threatened population, we elucidate the current situation here by using as examples three different megavertebrate families: elephantidae, rhinoceridae and giraffidae. These mammal families consist of charismatic species, and most of their members are currently facing dramatic declines in population numbers. On the basis of these and other examples, we highlight the importance of captive zoo and other managed wildlife populations for species survival in a human dominated world. Without the possibility to study reproductive physiology in trained or habituated captive individuals, major advances made in wildlife ART during the past 20 years would not have been possible. This paper reviews the benefits and future challenges of large mammal conservation breeding and examines the role of assisted reproduction in such efforts.

A predictive model to diagnose pregnancy in guanacos (Lama guanicoe) using non-invasive methods

Pregnancy status is usually not included in ecological studies because it is difficult to evaluate. The use of non-invasive methods to determine pregnancy, without physically restraining individuals, would enable pregnancy to be included in population studies. In this study, we evaluated sex steroid hormones in plasma and fecal samples from pregnant and non-pregnant females to develop a pregnancy predictive model for guanacos (Lama guanicoe (Müller, 1776)). Samples were obtained during live-shearing management (i.e., capture, shear, and release) of guanacos. Enzyme immunoassays were used to evaluate progesterone (P4) and estradiol (E2) concentrations in plasma and pregnanediol glucuronides (PdG) and conjugated estrogens (EC) in feces. Mean hormonal and fecal metabolite concentrations were significantly higher in pregnant females than in non-pregnant females. A linear relationship was found between each hormone and its fecal metabolite. Finally, hormonal data were combined with an independent source of pregnancy diagnosis such as abdominal ballottement to develop a logistic regression model to diagnose pregnancy in non-handled individuals. The use of predictive models and non-invasive methods might be suitable to incorporate pregnancy information in large-scale population studies on guanaco and other free-ranging ungulates.

Urinary estrogens as a non-invasive biomarker of viable pregnancy in the giant panda (Ailuropoda melanoleuca)

Female giant pandas show complex reproductive traits, being seasonally monoestrus, displaying a variable length embryonic diapause and exhibiting pseudopregnancy. Currently, there is no confirmatory non-invasive biomarker of blastocyst implantation or pregnancy. This study aimed to monitor urinary estrogens across gestation in pregnancy (n = 4), pseudopregnancy (n = 4) and non-birth cycles (n = 5) in the giant panda. A pregnancy-specific profile of estrogens corrected for urinary specific gravity was identified during the gestation period. Pregnant females showed increasing concentrations of estrogens for 29 days until birth, no increase was observed during pseudopregnancy and the two profiles were distinguishable from each other for the final 2 weeks of the cycle suggesting the estrogens are of placental origin. This allowed a nomogram, starting at a known fixed point during the cycle, to be created and tested with cycles of known outcome, and cycles which were inseminated but did not result in a birth. Non-birth profiles showed deviations from that of pregnancy. We believe these deviations indicate the point of failure of the placenta to support a developing cub. Non-invasive longitudinal monitoring of estrogen concentrations therefore has the potential to be developed as a panda pregnancy test to predict viable cub development.

Evaluation of fecal hormones for noninvasive research on reproduction and stress in humpback whales (Megaptera novaeangliae)

Fecal hormone analysis shows high potential for noninvasive assessment of population-level patterns in stress and reproduction of marine mammals. However, the marine environment presents unique challenges for fecal sample collection. Data are still lacking on collection methodology and assay validations for most species, particularly for those mysticete whales that have variable diets. In this study we tested collection techniques for fecal samples of free-swimming humpback whales (Megaptera novaeangliae), and validated immunoassays for five steroid and thyroid hormones. Resulting data were used for preliminary physiological validations, i.e., comparisons to independently confirmed sex and reproductive state. Pregnant females had significantly higher fecal progestins and glucocorticoids than did other demographic categories of whales. Two possible cases of previously undetected pregnancies were noted. Males had significantly higher fecal testosterone metabolites than nonpregnant females. Fecal glucocorticoids were significantly elevated in pregnant females and mature males compared to nonpregnant females. Calf fecal samples had elevated concentrations of all fecal hormones. Fecal thyroid hormones showed a significant seasonal decline from spring to summer. Though sample sizes were small, and sampling was necessarily opportunistic, these patterns indicate that noninvasive fecal hormone analysis may facilitate studies of reproduction, stress and potentially energetics in humpback whales.

Identification of feline Kiss1 and distribution of immunoreactive kisspeptin in the hypothalamus of the domestic cat

In recent years, the Kiss1 gene has been reported in a number of vertebrate species, and a substantial dataset has been acquired to demonstrate the critical role of kisspeptins in the reproductive system; yet limited information is available for carnivores. In the present study, we identified and characterized feline Kiss1 by isolating and cloning its full-length cDNA in the domestic cat hypothalamus and caracal testis, using the method of rapid amplification of cDNA ends. Additionally, we isolated and cloned the 3′ end of Kiss1 cDNA, containing kisspeptin-10 (Kp10), from the ovaries of a clouded leopard and Siberian tiger. Nucleotide sequencing revealed that domestic cat Kiss1 cDNA is of 711 base pairs and caracal Kiss1 cDNA is of 792 base pairs, both having an open reading frame of 450 base pairs, encoding a precursor protein Kiss1 of 149 amino acids. The core sequence of the feline kisspeptin Kp10 was found to be identical in all species analyzed here and is highly conserved in other vertebrate species. Using an anti-Kp10 antibody, we found the immunoreactive kisspeptin to be localized in the periventricular and infundibular nuclei of the cat hypothalamus. The results show that kisspeptin is highly conserved among different feline families, and its immunoreactive distribution in the hypothalamus may indicate its physiological function in the domestic cat.

Opportunities and challenges associated with fecal progesterone metabolite analysis

Conventionally, plasma or milk progesterone evaluations are used to determine the reproductive status of female animals. Collection of such samples is often associated with difficulties of animal handling and restraint. Measurable quantities of progesterone metabolites are found in feces of animals. Their concentrations are known to be well correlated to plasma progesterone levels and are, therefore, used as non-invasive samples for assessing reproductive function in a wide range of animal species. Although the analysis of fecal progesterone metabolites has been widely accepted in many laboratories, several factors are known to affect the results from this valuable analytical technique. Some of these factors include storage/transportation media for fecal samples, type of solvent that is used for extraction of progesterone metabolites from feces, and the type and sensitivity of an assaying technique employed. Although fecal progesterone metabolites analysis is associated with some difficulties, it can effectively be used to monitor reproductive function in a wide range of animal species. This review aims to highlight the usefulness of fecal progesterone metabolite analysis as a non-invasive technique in monitoring reproductive function in animals. The article mainly focuses on the many opportunities and challenges associated with this analytical technique.

The mutual benefits of research in wild animal species and human-assisted reproduction

Studying the reproductive biology of wild animal species produces knowledge beneficial to their management and conservation. However, wild species also share intriguing similarities in reproductive biology with humans, thereby offering alternative models for better understanding the etiology of infertility and developing innovative treatments. The purpose of this review is to raise awareness in different scientific communities about intriguing connections between wild animals and humans regarding infertility syndromes or improvement of fertility preservation. The objectives are to (1) highlight commonalities between wild species and human fertility, (2) demonstrate that research in wild species-assisted reproductive technologies can greatly enhance success in human reproductive medicine, and (3) recognize that human fertility preservation is highly inspiring and relevant to wild species conservation. In addition to having similar biological traits in some wild species and humans, the fact of sharing the same natural environment and the common needs for more options in fertility preservation are strong incentives to build more bridges that will eventually benefit both animal conservation and human reproductive medicine.