Semen cryopreservation in the Indian rhinoceros (Rhinoceros unicornis)

Genetic load and viability of a future restored northern white rhino population

As biodiversity loss outpaces recovery, conservationists are increasingly turning to novel tools for preventing extinction, including cloning and in vitro gametogenesis of biobanked cells. However, restoration of populations can be hindered by low genetic diversity and deleterious genetic load. The persistence of the northern white rhino (Ceratotherium simum cottoni) now depends on the cryopreserved cells of 12 individuals. These banked genomes have higher genetic diversity than southern white rhinos (C. s. simum), a sister subspecies that successfully recovered from a severe bottleneck, but the potential impact of genetic load is unknown. We estimated how demographic history has shaped genome-wide genetic load in nine northern and 13 southern white rhinos. The bottleneck left southern white rhinos with more fixed and homozygous deleterious alleles and longer runs of homozygosity, whereas northern white rhinos retained more deleterious alleles masked in heterozygosity. To gauge the impact of genetic load on the fitness of a northern white rhino population restored from biobanked cells, we simulated recovery using fitness of southern white rhinos as a benchmark for a viable population. Unlike traditional restoration, cell-derived founders can be reintroduced in subsequent generations to boost lost genetic diversity and relieve inbreeding. In simulations with repeated reintroduction of founders into a restored population, the fitness cost of genetic load remained lower than that borne by southern white rhinos. Without reintroductions, rapid growth of the restored population (>20-30% per generation) would be needed to maintain comparable fitness. Our results suggest that inbreeding depression from genetic load is not necessarily a barrier to recovery of the northern white rhino and demonstrate how restoration from biobanked cells relieves some constraints of conventional restoration from a limited founder pool. Established conservation methods that protect healthy populations will remain paramount, but emerging technologies hold promise to bolster these tools to combat the extinction crisis.

Increasing the Yield and Cryosurvival of Spermatozoa from Rhinoceros Ejaculates Using the Enzyme Papain

Simple Summary

Efficient collection and cryosurvival of semen from threatened wildlife species is key for the success of artificial reproductive technologies (ARTs). The viscous nature of ejaculates often collected from species such as rhinoceros, elephant, hippopotamus and primate, render the majority of spermatozoa collected useless and is therefore wasted. The enzyme papain has been used to reduce the viscosity of camelid semen but has yet to be tested in wildlife species. Therefore, the current study investigated the ability of papain to improve the yield and quality of spermatozoa collected from viscous fractions of the rhinoceros ejaculate during cryopreservation. Papain increased the quantity of useable spermatozoa collected from ejaculates, as well as the motility prior to freezing. It also improved the post-thaw motility, velocity, linearity and straightness of samples compared to spermatozoa frozen from the sperm-rich fraction of the ejaculate. There was no detrimental effect on membrane characteristics or DNA integrity. These results show that treating rhinoceros ejaculates with papain is able to salvage valuable spermatozoa and improve survival post-thaw, ultimately increasing the success of ARTs and creation of biobanks for the maintenance and survival of threatened species.

Abstract

The preservation of rhinoceros semen is vital for captive breeding programs. While successful collection and cryopreservation of rhinoceros semen has been reported, the volume and quality of semen produced is often low due to the high viscosity associated with ejaculates collected via electroejaculation. Reducing semen viscosity would enable access to previously unusable spermatozoa from viscous fractions and could improve quality post-thaw. The enzyme papain successfully reduced the viscosity of camelid semen but has yet to be tested in wildlife species. This study assessed the influence of papain on the in vitro quality of rhinoceros spermatozoa during cryopreservation using advanced semen assessment. In experiment 1, the motility of spermatozoa from the viscous fraction of an ejaculate, either untreated or treated with papain and its inhibitor E-64 prior to cryopreservation, was assessed post-thaw. In experiment 2, spermatozoa from papain-treated viscous fractions were compared to spermatozoa frozen from untreated sperm-rich fractions pre-freeze, as well as after 0, 1.5 and 3 h of incubation post-thaw (37 °C). Papain significantly increased the quantity of spermatozoa collected from ejaculates, as well as the motility prior to freezing. Papain also improved the post-thaw motility, velocity, linearity and straightness of samples compared to sperm-rich samples, with no detriment to sperm viability, lipid membrane disorder, production of ROS or DNA integrity (p < 0.05). Results show the benefit of supplementing rhinoceros spermatozoa with papain prior to cryopreservation on sperm cryosurvival and demonstrates the potential of using papain to improve the success of cryopreservation protocols, not only for the rhinoceros, but also for other wildlife species.

Anti-Müllerian hormone in managed African and Asian rhino species

Serum collected across the lifespan of four managed rhino species: black (Diceros bicornis, n = 16), white (Ceratotherium simum simum, n = 19), greater one-horned (GOH, Rhinoceros unicornis, n = 11) and Sumatran (Dicerorhinus sumatrensis, n = 6) were validated and analyzed in an anti-Müllerian hormone (AMH) enzyme- linked immunoassay. Concentrations of AMH were examined over time, between sexes and throughout different reproductive states which included n = 3 female white rhinos immunocontracepted with porcine zona pellucida (pZP). Across species, males produced higher AMH concentrations compared to females. Among males, AMH concentrations varied by species aside from comparable values secreted between black and white rhinos. The GOH and Sumatran rhino secreted the highest and lowest male AMH concentrations, respectively. However, within each species, AMH concentrations were similar across male age categories. Preliminary insight into male AMH changes from birth to sexual maturity suggest its potential as a marker for onset of testicular maturation. Female black, GOH and Sumatran rhinos secreted comparable AMH concentrations which were higher than those in white rhino. Within each species, inter-individual variation in AMH secretion occurred among females of similar age. While AMH secretion did not differ across the ages sampled for female white (4->26 yr) and GOH (4-26 yr) rhinos, black and Sumatran rhinos >26 and <4 yr, respectively secreted lower AMH compared to conspecific females 7-26 yr of age. Two idiopathic infertility cases corresponded to low (outside species range) AMH values. The establishment of normative AMH concentrations in managed African and Asian rhinos provides an additional metric beyond traditional sex steroids to assess gonadal function. Further work is needed to determine if AMH can predict fertility potential in rhinos.

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.

Animal protein-free OptiXcell and shortened equilibration periods can replace egg yolk-based extender and slow cooling for rhinoceros semen cryopreservation

OptiXcell (OP) was tested as an animal protein-free alternative to an egg yolk-based extender for rhinoceros semen cryopreservation and shorter chilling/equilibration periods were evaluated. Semen was collected from three rhinoceros species: black (Diceros bicornis; n = 2), white (Ceratotherium simum; n = 2), and greater one-horned (GOH; Rhinoceros unicornis; n = 3). Controls were diluted with equine extender (EQ) or OP and equilibrated for 1 h. Treatments were diluted with extender and cooled for 15 min (fast: FEQ; FOP) or not cooled (immediate: IEQ; IOP), prior to cryopreservation. Motility decreased post-thaw (EQ: 50.7 ± 5.2%; OP: 52.9 ± 3.4%) from fresh (82.9 ± 2.9%), was higher in OP than IOP (38.6 ± 4.9%; P ≤ 0.05) and decreased over time (P ≤ 0.05). Post-thaw acrosomal integrity was lower in EQ, FEQ, and IEQ (56.9 ± 0.7; 56.6 ± 4.5; 54.9 ± 2.9%) than OP, FOP, IOP (71.8 ± 4.7; 71.9 ± 3.8; 69.9 ± 4.5%) and fresh (72.6 ± 1.4%; P ≤ 0.05). Progression and viability were lower in EQ (2.8 ± 0.2; 61.9 ± 7.4%) and OP (3.1 ± 0.2; 53.4 ± 6.9%) than fresh (3.7 ± 0.2; 87.2 ± 1.3%), decreased over time (P ≤ 0.05) but not different among treatments (P > 0.05). Morphology did not differ between fresh (75.0 ± 4.9% normal) and any treatment group (70.0-77.8%) or over time (P > 0.05). OptiXcell is comparable to egg yolk-based EQ when used for rhinoceros semen cryopreservation. Furthermore, chilling/equilibration can be reduced with little impact on sperm characteristics.

Strong Heterogeneity in Advances in Cryopreservation Techniques in the Mammalian Orders

Between 1970 and 2012, vertebrate abundance has declined by 58% with an average annual decline of 2%, calling for serious action to prevent a mass extinction and an irreversible loss of biodiversity. Cryobanks and cryopreservation have the potential to assist and improve ex situ and in situ conservation strategies by storing valuable genetic material. A great deal of studies concerning cryopreservation have been performed within the class Mammalia, although no systematic overview has previously been presented. The objective of this study is therefore to evaluate the status, pattern and future of cryopreservation within Mammalia. A strong disproportional distribution of studies in examined orders is displayed. For the majority of examined orders less than 10% of species has been examined. However, the cryopreservation of germplasm has in several cases been successful and resulted in successful applications of assisted reproductive techniques (ARTs). Various obstacles are associated with the development of cryopreservation protocols, and among them the most prominent is interspecific differences in cryotolerance. Extrapolation of protocols in closely related species is considered the most applicable procedure, and a future supplement to overcome this problem is the examination and comparison of cryobiological traits. Successful protocols have been developed for the vast majority of domesticated mammals, which gives incentive for the further extrapolation of protocols in threatened species.

Comparison of soy lecithin, coconut water, and coconut milk as substitutes for egg-yolk in semen cryodiluent for black rhinoceros (Diceros bicornis) and Indian rhinoceros (Rhinoceros unicornis)

Semen cryopreservation for the black rhinoceros (Diceros bicornis) and Indian rhinoceros (Rhinoceros unicornis) relies on extenders containing egg-yolk (EY). Use of such media is not ideal as inter-batch composition varies and there is risk of pathogenic contamination. The goal of this study was to test animal protein-free extenders. Semen collected via electroejaculation from 10 rhinoceros (6 black, 4 Indian) was diluted with extender containing EY, 1% or 2% soy lecithin (1%SL; 2%SL), coconut water (CW), or coconut milk (CM), cryopreserved and evaluated for sperm motility, viability, morphology, progression, and acrosomal integrity at 0, 1, 3, 6 and 24 h post-thaw. Mean ± SD fresh ejaculate motility was 84.5 ± 7.6%, progression: 3.6 ± 0.6 (scale 0-5), viability: 83.4 ± 7.1%, intact acrosomes: 71.3 ± 6.9%, and morphologically normal: 78.8 ± 13.6%. Motility and progression decreased in all groups post-thaw, were greatest in EY, and decreased over time (P ≤ 0.05). Motility and progression did not differ (P > 0.05) between 1%SL and 2%SL, but were lower (P ≤ 0.05) in CM and CW, and acrosomal integrity was higher (P ≤ 0.05) in EY, 1%SL and 2%SL than in CM and CW. Post-thaw viability was greatest in EY and 2%SL followed by 1%SL, then CM and CW (P ≤ 0.05). Morphology did not differ among treatments (P > 0.05). Morphology, acrosomal integrity, and viability were maintained over time (P > 0.05). Although some rhinoceros sperm survived cryopreservation in SL treatments, reduced post-thaw motility rendered all treatments inadequate substitutes for EY-based extenders.

Cryopreservation in rhinoceros-Setting a new benchmark for sperm cryosurvival

At times when rhinoceros are fiercely poached, when some rhinoceros species are closer than ever to extinction, and when the scientific community is in debate over the use of advanced cell technologies as a remaining resort it is time to simplify and improve existing assisted reproduction techniques to enhance breeding and genetic diversity in the living populations under our care. Semen cryopreservation has been performed in all captive rhinoceros species with limited degree of success. Here we tested three freezing extenders, containing different cryoprotectants and various freezing rates for the cryopreservation of rhinoceros sperm from 14 bulls. In experiment I, semen from 9 bulls was used to determine the most suitable diluent, cryoprotectant and freezing rate for the successful cryopreservation of rhinoceros sperm. In experiment II, semen from 5 bulls was used to assess whether the removal of seminal plasma could further improve post thaw sperm quality following cryopreservation with conditions identified in Experiment I. Semen was diluted with Berliner Cryomedia, ButoCrio® or INRA Freeze®, packaged in 0.5 mL straws and frozen 3, 4, and 5 cm over liquid nitrogen (LN) vapour or directly in a dryshipper. It was found that semen extended with ButoCrio® (containing glycerol and methylformamide) and frozen 3cm over LN vapour provided the best protection to rhinoceros spermatozoa during cryopreservation. When pooled over treatments, total and progressive post thaw motility was 75.3 ± 4.2% and 68.5 ± 5.7%, respectively marking a new benchmark for the cryopreservation of rhinoceros sperm. Post thaw total and progressive motility, viability and acrosome integrity of semen diluted in ButoCrio® was significantly higher than semen extended in Berliner Cryomedia or INRA Freeze®. The removal of seminal plasma did not improve post thaw sperm survival (p > 0.05). In conclusion, the cryosurvival of rhinoceros spermatozoa was significantly improved when using a mixture of glycerol and methylformamide in combination with a fast freezing rate at 3 cm. These results describe a new protocol for the improved cryosurvival of rhinoceros spermatozoa and will enable a more successful preservation of genetic diversity between males, especially in donors whose spermatozoa may already be compromised prior to or during collection. The successful reduction of glycerol concentration in favour of methylformamide as a cryoprotectant could be a novel suggestion for the improvement of cryopreservation techniques in other wildlife species.

Enhancing captive Indian rhinoceros genetics via artificial insemination of cryopreserved sperm

The objective of this study was to design an artificial insemination (AI) protocol using cryopreserved spermatozoa to obtain pregnancies in captive Indian rhinoceroses (Rhinoceros unicornis). Four methods developed varied by timing and approach, as follows; Method 1: females (n=2) were inseminated pre- and post-ovulation under general anesthesia, Method 2: females (n=2) were inseminated pre-ovulation without anesthetic via endoscopy, Method 3: females (n=1) were inseminated pre-ovulation without anesthetic via manual insertion of an insemination catheter, Method 4: females (n=2) were inseminated same as Method 3 with the addition of standing sedation. Semen deposition site varied as a result of changes in AI technology and experience. All females conceived following intrauterine AI using three methods. Four pregnancies (n=3 females) produced via Method 3 and 4 resulted in term births (n=2 male calves, n=2 female calves) at 481.8±12.8days post-AI. Unfortunately, two early pregnancy losses were documented in a fourth female conceiving via Method 2. Pregnancy rates were 0%, 22%, 17%, and 50% for Method 1-4, respectively. Method 3 and 4 rates improved to 29% and 67%, respectively when accounting for AI's conducted only on ovulatory estrous cycles. Spermatozoa (n=5 males) were cryopreserved 0.3-9.3 y prior to successful AI procedures. The lowest dose of frozen-thawed sperm resulting in conception was 500×10(6) motile sperm. Mean time from AI to ovulation in conceptive and non-conceptive cycles was 26±11.8h and 66±80.7h, respectively.

Biobanking efforts and new advances in male fertility preservation for rare and endangered species

Understanding and sustaining biodiversity is a multi-disciplinary science that benefits highly from the creation of organized and accessible collections of biomaterials (Genome Resource Banks). Large cryo-collections are invaluable tools for understanding, cataloging, and protecting the genetic diversity of the world's unique animals and plants. Specifically, the systematic collection and preservation of semen from rare species has been developed significantly in recent decades with some biobanks now being actively used for endangered species management and propagation (including the introduction of species such as the black-footed ferret and the giant panda). Innovations emerging from the growing field of male fertility preservation for humans, livestock species, and laboratory animals are also becoming relevant to the protection and the propagation of valuable domestic and wild species. These new approaches extend beyond the “classical” methods associated with sperm freezing to include testicular tissue preservation combined with xenografting or in vitro culture, all of which have potential for rescuing vast amounts of unused germplasm. There also are other options under development that are predicted to have a high impact within the next decade (stem cell technologies, bio-stabilization of sperm cells at ambient temperatures, and the use of genomics tools). However, biobanking efforts and new fertility preservation strategies have to expand the way beyond mammalian species, which will offer knowledge and tools to better manage species that serve as valuable biomedical models or require assistance to reverse endangerment.

Saving wild ungulate diversity through enhanced management and sperm cryopreservation

Wild ungulates throughout the world face the impending risk of extinction. Small founding population size, lack of interest in exhibiting wild ungulates and declining space in zoos are not sustaining ex situ populations. Animals managed in ex situ collections continue to experience >20% neonate loss globally. To ensure population sustainability there is a critical need to: (1) manage ungulates in large herds, increasing mate choice and reproductive efficiency; (2) improve husbandry and genetic management; and (3) develop consistent assisted reproductive technologies, including sperm cryopreservation and AI. Recently, new models in the management of ungulates have begun to emerge. Animal managers and researchers are also beginning to exploit advances in genomics to improve genetic management of their collections. Furthermore, the past decade has witnessed significant advances particularly in semen collection and cryopreservation in numerous species. Advances in gonadal tissue cryopreservation now offer additional opportunities to preserve male genomes. The new knowledge generated is enabling the creation of genetic (sperm) banks to rescue and enhance reproductive management of wild ungulates. The present paper reviews the threats to ungulate populations, the status and relevance of animal management and biomaterial banking efforts to ensure long-term survival of these charismatic species.

Sperm sex-sorting and preservation for managing the sex ratio and genetic diversity of the southern white rhinoceros (Ceratotherium simum simum)

White rhinoceros ejaculates (n=9) collected by electroejaculation from four males were shipped (10°C, 12h) to develop procedures for the production of chilled and frozen-thawed sex-sorted spermatozoa of adequate quality for artificial insemination (AI). Of all electroejaculate fractions, 39.7% (31/78) exhibited high quality post-collection (≥70% total motility and membrane integrity) and of those, 54.8% (17/31) presented reduced in vitro quality after transport and were retrospectively determined to exhibit urine-contamination (≥21.0μg creatinine/ml). Of fractions analyzed for creatinine concentration, 69% (44/64) were classified as urine-contaminated. For high quality non-contaminated fractions, in vitro parameters (motility, velocity, membrane, acrosome and DNA integrity) of chilled non-sorted and sorted spermatozoa were well-maintained at 5°C up to 54h post-collection, whereby >70% of post-transport (non-sorted) or post-sort (sorted) values were retained. By 54h post-collection, some motility parameters were higher (P<0.05) for non-sorted spermatozoa (total motility, rapid velocity, average path velocity) whereas all remaining motion parameters as well as membrane, acrosome and DNA integrity were similar between sperm types. In comparison with a straw method, directional freezing resulted in enhanced (P<0.05) motility and velocity of non-sorted and sorted spermatozoa, with comparable overall post-thaw quality between sperm types. High purity enrichment of X-bearing (89±6%) or Y-bearing (86±3%) spermatozoa was achieved using moderate sorting rates (2540±498X-spermatozoa/s; 1800±557Y-spermatozoa/s). Collective in vitro characteristics of sorted-chilled or sorted-frozen-thawed spermatozoa derived from high quality electroejaculates indicate acceptable fertility potential for use in AI.

Mammalian fertility preservation through cryobiology: value of classical comparative studies and the need for new preservation options

Human-related fertility preservation strategies have enormous potential for helping sustain and protect other species, especially to assist managing or 'rescuing' the genomes of genetically valuable individuals, including endangered species. However, wider-scale applications are limited by significant physiological variations among species, as well as a lack of fundamental knowledge of basic reproductive traits and cryosensitivity. Systematic and comparative cryopreservation studies (e.g. on membrane biophysical properties and resilience to freezing temperatures) are required to successfully recover gametes and gonadal tissues after thawing and eventually produce healthy offspring. Such data are currently available for humans and a few laboratory and livestock animals, with virtually all other species, including wildlife, having gone unstudied. Interestingly, there also are commonalities among taxa that allow a protocol developed for one species to provide useful information or guidance for another. However, when a rare animal unexpectedly dies there is no time for a prospective understanding of that species' biophysical traits. Because the odds of success will be much lower in such instances, it is essential that more fundamental studies be directed at more species. But also worthwhile is thinking beyond these systematic characterisations to consider the potential of a 'universal preservation protocol' for animal biomaterials.

Recent advances and prospects in germplasm preservation of rare and endangered species

Fertility preservation strategies using cryopreservation have enormous potential for helping sustain and protect rare and endangered species, especially to assist managing or 'rescuing' the genomes of genetically valuable individuals. However, wide-scale applications are still limited by significant physiological variations among species and a sheer lack of fundamental knowledge about basic reproductive traits as well as in germplasm cryobiology. Cryo-studies have been conducted in more species (mainly vertebrates) in the recent years but a vast majority still remains un-studied. Semen cryopreservation represents the most extensive effort with live births reported in more and more species after artificial insemination. Oocyte freezing remains challenging and unsuccessful in wild species and will require more research before becoming a standard procedure. As an alternative to fully grown gametes, gonadal tissue preservation has become a promising option in vertebrates. Yet, more fertility preservation options are necessary to save species so a change in strategy might be required. It is worthwhile thinking beyond systematic characterizations and considering the application of cutting edge approaches to universally preserve the fertility of a vast array of species.

Fresh semen quality in ejaculates produced by nocturnal emission in men with idiopathic anejaculation

OBJECTIVE

To compare the quality of fresh semen samples collected by nocturnal emission (NE), penile vibratory stimulation (PVS), or electroejaculation (EEJ) from idiopathic anejaculation patients with those collected by masturbation from healthy control subjects.

DESIGN

Retrospective clinical study.

SETTING

University medical center.

PATIENT(S)

Ninety-one men with idiopathic anejaculation.

INTERVENTION(S)

NE, PVS, EEJ, computer-assisted semen analysis system.

MAIN OUTCOME MEASURE(S)

Sperm volume, concentration, motility, and morphology.

RESULT(S)

The mean percentage of motile sperm in the NE group was 30.6% ± 3.5% (range 11.2%-50.9%), which is 1.5- and 1.9-fold higher than that of the PVS (20.5% ± 1.3%, range 6.9%-40.2%) and EEJ (16.1% ± 0.9%, range 3.7%-27.3%) groups, respectively. The percentage of sperm that have normal morphology in the NE group was 61.4% ± 4.8%, which is significantly higher than that in the PVS (38.4% ± 2.8%) and EEJ groups (29.5% ± 1.7%), respectively. However, compared with the healthy control group, the sperm motility and normal morphology in the NE, PVS, and EEJ groups were significantly lower. The sperm concentration in the NE group (149.4 ± 16.3 × 10(6) mL(-1)) was similar to that of the PVS group (143.8 ± 13.1 × 10(6) mL(-1)) but was higher than in the EEJ group (96.3 ± 8.6 × 10(6) mL(-1)) and lower than in the control group (225.0 ± 15.0 × 10(6) mL(-1)). Furthermore, the semen volume in the NE group (2.6 ± 0.2 mL) was lower than that of the control group (3.0 ± 0.1 mL).

CONCLUSION(S)

This study is the first to report on the quality of fresh semen obtained by NE in patients with idiopathic anejaculation. Sperm motility and normal morphology were higher in patients who collected sperm by NE than in those who collected sperm by PVS and EEJ.

Comparative cryobiological traits and requirements for gametes and gonadal tissues collected from wildlife species

A major challenge to retaining viability of frozen gametes and reproductive tissues is to understand and overcome species-specificities, especially because there is substantial diversity in cryobiological properties and requirements among cell types and tissues. Systematic studies can lead to successful post-thaw recovery, especially after determining: 1) membrane permeability to water and cryoprotectant, 2) cryoprotectant toxicity, 3) tolerance to osmotic changes, and 4) resistance to cooling and freezing temperatures. Although species-dependency ultimately dictates the ability of specific cells and tissues to survive freeze-thawing, there are commonalities between taxa that allow a protocol developed for one species to be useful information for another. This is the reason for performing comparative cryopreservation studies among diverse species. Our laboratory has compared cellular cryotolerance, especially in spermatozoa, in a diverse group of animals-from corals to elephants-for more than 30 yrs. Characterizing the biophysical traits of gametes and tissues is the most efficient way to develop successful storage and recovery protocols, but, such data are only available for a few laboratory, livestock, and fish species, with virtually all others (wild mammals, birds, reptiles, and amphibians) having gone unstudied. Nonetheless, when a rare animal unexpectedly dies, there is no time to understand the fundamentals of biophysics. In these emergencies, it is necessary to rely on experience and the best data from taxonomically-related species. Fortunately, there are some general similarities among most species, which, for example, allow adequate post-thaw viability. Regardless, there is a priority for more information on biophysical traits and freezing tolerance of distinctive biomaterials, especially for oocytes and gonadal tissues, and even for common, domesticated animals. Our colleague, Dr John Critser was a pioneer in cryobiology, earning that moniker because of his advocacy and devotion to understanding the differences (and similarities) among species to better store living genetic material.

Alkaline phosphatase as an indicator of true ejaculation in the rhinoceros

The objective was to determine if seminal alkaline phosphatase (ALP) can serve as an indicator of true ejaculation in the rhinoceros. Concentrations of ALP activity were determined in seminal fractions collected from African black rhinos (Diceros bicornis), an African white rhino (Ceratotherium simum), and an Indian rhino (Rhinoceros unicornis) during electroejaculation. In addition, seminal fractions collected during penile massage of a Sumatran rhino (Dicerorhinus sumatrensis) were assessed. Correlations between ALP activity and sperm concentration, fraction pH, and fraction osmolality were evaluated in the Indian rhino and black rhino. Concentrations of ALP activity in rhino ejaculate fractions ranged from < 5 to 11,780 U/L and were positively correlated (P < 0.05) with sperm concentration for both Indian rhino (r = 0.995) and black rhino (r = 0.697), but did not exhibit a strong correlation with either pH or osmolality (P > 0.05). Data were insufficient for establishing meaningful correlation coefficients in the Sumatran rhino and white rhino, but preliminary results were in accordance with findings in the Indian rhino and black rhino. We concluded that ALP was present in rhinoceros semen, likely originated from the epididymides and/or testes, and could serve as a useful tool for assessing the production of ejaculatory versus pre-ejaculatory fluid in the rhinoceros.