Cryopreservation of jaguar (Panthera onca) sperm cells using different cryoprotectants and different thawing temperatures

The cryopreservation of jaguar semen must be improved to produce high-quality biobanking doses. Until now, the rare studies of semen freezing in the species have only evaluated glycerol, always with a significant reduction in sperm quality in thawed semen. The purpose of this study was to assess the efficacy of three cryoprotectants, dimethylsulfoxide (DMSO), glycerol (GLY), and methanol (MET), in the cryopreservation of jaguar semen in an LDL-based extender, as well as the effect of thawing temperature on dosage quality. Five mature males with a history of reproduction were used. On the males, an infrared thermal image (IRT) was captured, the spicules and testes were analyzed, and the CASA system was used to evaluate the quality of fresh and thawed sperm. The superficial IRT was 4.6 ± 1.2 °C cooler than the anal sphincter, and the semen measured between 27.3 and 28.7 °C shortly after exiting the urethra. The total motility of fresh sperm was 55.3 ± 22.6%, and progressive motility was 36.3 ± 18%. The total motility of thawed sperm was 5.28 ± 2.51%, 4.49 ± %2.49, and 0.51 ± 0.62% for DMSO, GLY, and MET, respectively. DMSO and GLY performed better than MET, and there was no difference in thawing temperature (37°C 30 s vs. 50°C 12 s). All animals exhibit a considerable level of morphological changes in sperm. Low amounts of total and progressive motility were found in the thawed sperm. Males with a high level of sperm morphological changes were found to be fertile, but the lone male with normospermia was infertile. Thus, we contest the applicability of the commonly used morphological classification for bovines to felid species.

Semen collection, evaluation, and cryopreservation in the bonobo (Pan paniscus)

Background

Captive breeding of bonobos (Pan paniscus) has proven to be successful, but maintaining genetic diversity remains a challenge. Cryopreservation of semen is an important potential tool to maintain genetic diversity by preserving current genetic material for future use, as well as facilitating the transport and exchange of genetic material. This study aimed to develop a protocol for semen collection and cryopreservation in the bonobo. Semen was collected from four healthy adult bonobos under general anesthesia during management translocation procedures. Semen collection utilizing urethral catheterization was not successful (n = 1), however, all males (n = 4) responded well to rectal probe electro-ejaculation. Immediately after collection, ejaculates were evaluated for color and admixtures, volume, motility, and concentration. Eosin-Nigrosin staining was prepared to evaluate morphology and viability. Ejaculates were split into two equal volumes and cryopreserved in two different extenders, using a one-step and a two-step approach. Ejaculates were gradually cooled to 4 °C in two hours, subsequently stored in liquid nitrogen vapor for twenty minutes (0.25 ml straws), and finally dropped into liquid nitrogen.

Results

Pre-freeze evaluation showed thick, white samples with an average ejaculate volume of 450 µl (100-1000 µl), total motility of 59% (40–80%), viability of 69% (38–85%) and 58% (46–72%) normal spermatozoa. Mainly head (22%) and tail (19%) defects were detected on the Eosin-Nigrosin stain. Ejaculates were highly concentrated, nevertheless, due to the coagulum that caused high viscosity and non-homogenous fractions, only estimations of concentration could be made (1000 million/ml). After 24 h of storage, the post-thaw evaluation showed a loss of quality with an average post-thaw total motility of 15% (5–25%) using the one-step freezing medium, and 19% (5–30%) using the two-step medium. Average post-thaw viability was 15% (4–24%) and 21% (15–29%), respectively.

Conclusions

This report on ejaculates from bonobos obtained by rectal probe electro-ejaculation shows that semen parameters of this species are not completely similar to those of its sibling species, the chimpanzee. Further studies are necessary to develop an optimal protocol for the processing and cryopreservation of bonobo spermatozoa.

Spermatic profile of captive giant anteaters (Myrmecophaga tridactyla): Knowing more to preserve better

The giant anteater (Myrmecophaga tridactyla) is being threatened by natural habitat destruction and fragmentation, illegal hunting and road kills. In this context, the generation of basic information on the reproductive parameters of this species is vital, aiming to improve reproductive management via, amongst others, assisted reproductive technologies. This study aimed to describe the morphological and functional features of semen collected from captive giant anteaters. Electroejaculation was performed in 13 animals housed in zoos located in São Paulo state, Brazil. Semen samples were collected from 13 animals in 16 procedures. Samples were evaluated for volume, motility, vigor, pH, concentration, sperm morphology, and functional tests. The following mean values were obtained: volume 1.28 ± 0.27 mL; motility 28.3 ± 6.2%; vigor 2.4 ± 0.25; concentration 129.4 ± 36.1 × 10⁶ sperm/mL; pH 7.4 ± 0.2. Total acrosome, head, midpiece, and tail sperm abnormalities were 3.2 ± 0.8%, 25.4 ± 3.6%, 20.7 ± 3.2%, and 14.7 ± 2.6%, respectively. Intact acrosome was found in 83.7 ± 3.1% and intact membrane in 81.1 ± 4.0% of all samples collected. Mitochondrial activity was 66.4 ± 6.0% (Class I), 18.7 ± 2.9% (Class II), 8.0 ± 2.0% (Class III), 3.9 ± 1.0% (Class IV), and 3.0 ± 0.9% (Class V). Sperm DNA fragmentation rate was 13.2 ± 3.7%. These results indicated that electroejaculation is a feasible method for semen collection in giant anteaters, allowing a more detailed description of the semen in this species.

Sperm evaluation and morphological description of male genitalia of meerkats (Suricata suricatta)

In ex situ conditions, little is known about the reproductive biology of meerkats. The aim of present study was to describe the morphological aspects of male genital organs and accessory glands using macroscopic evaluation, ultrasonography, and radiography, as well as describing semen characteristics post-electroejaculation. The results indicated anatomical characteristics of meerkats are very similar to those of cats, having a prostate, accessory bulbourethral glands, and an elongated and radiopaque structure in the penis, which is indicative of there being a baculum. The testicular volume was 0.81 cm³ (± 0.10) and the relative testis weight was 1.37 cm³/kg (± 0.15). Both testicles are present in the scrotum, which has an ellipsoidal shape, homogeneous texture, hypoechoic parenchyma and are encased in a hyperechoic tunica albuginea. Electroejaculation was effectively induced in all animals for semen collection with utilization of medetomidine and ketamine. The values semen samples variables were as follows for volume - 0.125 ± 0.193 mL, motility - 19.8 ± 18.6 %, vigor - 1.9 ± 1.0, concentration - 40.5 ± 25.2 × 10⁶ sperm/mL and morphologically normal sperm - 10.8 ± 6.6 %. This is the first study in which there is a description of morphological and imaging aspects of the male reproductive tracts of meerkats, as well as the seminal characteristics after using electroejaculation for semen collection. Knowledge of anatomical and seminal characteristics is essential for implementation of assisted reproduction programs, as well as reproductive management in the species.

Urethral catheterization as an alternative method for collecting sperm in the black-footed ferret (Mustela nigripes)

The endangered black-footed ferret (BFF; Mustela nigripes) is an important example of the benefits of assisted reproduction in species conservation with both semen evaluation and artificial insemination using fresh and frozen sperm being successfully incorporated into the breeding program. Currently, electroejaculation (EE) is routinely utilized for semen collection in BFFs, a technique that requires custom equipment and experienced operators, and does not consistently yield viable samples in this species. In this case study, we evaluated the feasibility of urethral catheterization (UC) for semen collection, a method predominately tested in domestic and non-domestic felids, on four occasions (three BFF males). After general anesthesia with a combination of ketamine, midazolam and α2-agonist dexmedetomidine (thought to promote semen release into the urethra), a lightly lubricated, flexible feeding tube was passed into the urethral opening and advanced ~7-8 cm into the urethra. A syringe attached to the feeding tube was used to apply mild negative pressure to collect sperm. Semen samples were successfully collected on all four attempts. Sperm characteristics ranged as follows: 10.5-26.0 × 10⁶ sperm/ml concentration, 50-90% motility and 36-61% normal sperm morphology. This is the first report of the use of UC as a potential alternative to EE in the BFF, a more field-friendly technique that is less invasive and more consistent for obtaining samples free of urine contamination.

Sperm handling in aquatic animals for artificial reproduction

Artificial reproduction involves collection and handling of gametes in a way that secures their quality and maximizes the fertilization outcome. In addition to initial sperm quality, numerous steps can affect the final result of fertilization, from the sperm collection process until gamete mixing (or co-incubation) when the spermatozoon enters or fuses with the oocyte. In this review, we summarize the whole process of sperm handling, from collection until fertilization for fish, penaeid shrimp, bivalve mollusks and marine mammals. To obtain sperm from captive animals, techniques vary widely across taxa, and include stripping by abdominal massage or testis surgical removal in fish, spermatophore collection in penaeid shrimps, gonadal scarification or temperature shock in bivalve mollusks, and voluntary collection via positive reinforcement in mammals. In most cases, special care is needed to avoid contamination by mucus, seawater, urine, or feces that can either activate sperm motility and/or decrease its quality. We also review techniques and extender solutions used for refrigerated storage of sperm across the aforementioned taxa. Finally, we give an overview of the different protocols for in vivo and in vitro fertilization including activation of sperm motility and methods for gamete co-incubation. The present study provides valuable information regarding breeder management either for animal production or species conservation.

Effectiveness of urethral catheterization under ultrasound guidance for semen collection from Asiatic black bears (Ursus thibetanus)

The Asiatic black bear (ABB; Ursus thibetanus ussuricus) is a globally endangered species, and measures to help increase their population are necessary. For the successful restoration of this species, artificial breeding as well as conservation translocation are considered important. The aims of the present study were to evaluate the feasibility and effectiveness of urethral catheterization (UC), which is effectively used in feline species, for semen collection from ABBs and establish the optimal protocol for semen collection via this technique. Seven clinically healthy, adult male ABBs (age, 6-13 years; weight, 130-180 kg) housed at the Species Restoration Technology Institute, Korea were included in this study. All study procedures were performed during the breeding season (June to August) over 3 consecutive years. Semen samples were collected once or three times from all bears by ultrasound-guided UC or electroejaculation (EE) under general anesthesia, and their characteristics, including sperm motility, were evaluated. The day of semen collection was defined as Day 0. The semen collected by the UC method was stored at 4 °C, and sperm motility was evaluated at the same time every day for 16 days. The successful collection rates for the UC and EE methods were 92.3% and 53.8%, respectively. The sperm concentration (4718.9 ± 1526.1 vs. 185.0 ± 34.2 × 10⁶/ml), total sperm count (1196.6 ± 955.5 vs. 100.9 ± 70.0 × 10⁶), sperm motility score (4.39 ± 0.78 vs. 3.00 ± 1.73), viability (98.2 ± 2.3 vs. 82.7 ± 19.6), and the proportion of spermatozoa with intact acrosomes (92.2% ± 9.3% vs. 75.6% ± 10.6%) were higher with the UC method than with the EE method, whereas the proportion of spermatozoa with an abnormal morphology (23.1% ± 4.6% vs. 45.6% ± 19.5%) was lower with the former than with the latter. Over the course of cool storage, there was an overall decrease in the total motility, progressive motility, and viability, although viability was >50% until Day 10. These findings suggest that ultrasound-guided UC is a useful and feasible tool for the collection of high-quality semen from ABBs. The collected semen remains viable for up to 10 days, with high sperm motility maintained for up to 7 days, when stored at 4 °C.