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

Case Studies in Polar Bear (Ursus maritimus) Sperm Collection and Cryopreservation Techniques

Simple Summary

Polar bears are threatened by habitat loss, decreased food availability, and reduced reproductive success due to climate change. Zoo populations can support species survival through preservation of genetic diversity and maintenance of insurance populations, but in the US, the zoo polar bear population is currently not sustainable. The development of sperm collection and cryopreservation can help to support the population by providing the biomaterial needed for assisted reproductive techniques, such as artificial insemination. However, these procedures are not well described for polar bears. Data from 38 opportunistic sperm collections, that were conducted between 2011 and 2021, were assessed to establish best practices to date for collecting and preserving polar bear sperm. The information gathered demonstrates that urethral catheterization is an efficient method of sperm collection, sperm can be rescued postmortem from the vasa deferentia and epididymides, and polar bear sperm collection appears to be most effective during the breeding season. Furthermore, polar bear sperm can survive cryopreservation. Further studies will optimize these techniques, but this summary provides information that is immediately applicable to enhancing sample collection and cryopreservation success that could support the long-term genetic management of polar bears in zoos.

Abstract

Assisted reproductive technologies can aid conservation efforts via support of ex situ population management and preservation of genetic material. Data from 38 sperm collection attempts from 17 polar bears (1–5 procedures/bear) were evaluated. Sample collections were attempted via electroejaculation (EEJ; n = 6), urethral catheterization (UC; n = 25), or sperm rescue (SR; n = 7) during the breeding season (Jan. 1-May 21; n = 27) and nonbreeding season (May 22-Dec. 31; n = 11). Sperm retrieval was successful in 1 EEJ (16.7%), 18 UC (72.0%) and 4 SR (57.1%) collections. Initial sperm motility and viability were 50.0% and 77.0% for EEJ, 64.3 ± 7.4% and 80.9 ± 3.8% for UC, and 56.7 ± 8.8% and 80.5 ± 0.5% for SR. UC and SR were more likely to be successful during the breeding season (84.2–100%) than the nonbreeding season (25.0–33.3%). Testicular tumors were observed in four males (57%) during SR. In total, 13 samples were cryopreserved (n = 1 EEJ, 9 UC, and 3 SR) with egg-yolk-based equine extender (EQ) or OptiXcell (OP). For both extenders, post-thaw motility and viability were reduced by 20–60% and 30–65%, respectively. Further efforts to optimize procedures are warranted, but this summary provides data useful for enhancing the success of polar bear sperm collection and cryopreservation.

Status of Sperm Functionality Assessment in Wildlife Species: From Fish to Primates

(1) Background: in order to propagate wildlife species (covering the whole spectrum from species suitable for aquaculture to endangered species), it is important to have a good understanding of the quality of their sperm, oocytes and embryos. While sperm quality analyses have mainly used manual assessment in the past, such manual estimations are subjective and largely unreliable. Accordingly, quantitative and cutting-edge approaches are required to assess the various aspects of sperm quality. The purpose of this investigation was to illustrate the latest technology used in quantitative evaluation of sperm quality and the required cut-off points to distinguish the differential grades of fertility potential in a wide range of vertebrate species. (2) Methods: computer-aided sperm analysis (CASA) with an emphasis on sperm motility, 3D tracking and flagellar and sperm tracking analysis (FAST), as well as quantitative assessment of sperm morphology, vitality, acrosome status, fragmentation and many other complimentary technologies. (3) Results: Assessing sperm quality revealed a great deal of species specificity. For example, in freshwater fish like trout, sperm swam in a typical tight helical pattern, but in seawater species sperm motility was more progressive. In amphibian species, sperm velocity was slow, in contrast with some bird species (e.g., ostrich). Meanwhile, in African elephant and some antelope species, fast progressive sperm was evident. In most species, there was a high percentage of morphologically normal sperm, but generally, low percentages were observed for motility, vitality and normal morphology evident in monogamous species. (4) Conclusions: Sperm quality assessment using quantitative methodologies such as CASA motility, FAST analysis, morphology and vitality, as well as more progressive methodologies, assisted in better defining sperm quality-specifically, sperm functionality of high-quality sperm. This approach will assist in the propagation of wildlife species.

The ART of bringing extinction to a freeze - History and future of species conservation, exemplified by rhinos

The ongoing mass extinction of animal species at an unprecedented rate is largely caused by human activities. Progressive habitat destruction and fragmentation is resulting in accelerated loss of biodiversity on a global scale. Over decades, captive breeding programs of non-domestic species were characterized by efforts to optimize species-specific husbandry, to increase studbook-based animal exchange, and to improve enclosure designs. To counter the ongoing dramatic loss of biodiversity, new approaches are warranted. Recently, new ideas, particularly the application of assisted reproduction technologies (ART), have been incorporated into classical zoo breeding programs. These technologies include semen and oocyte collection, artificial insemination, and in-vitro embryo generation. More futuristic ideas of advanced ART (aART) implement recent advances in biotechnology and stem-cell related approaches such as cloning, inner cell mass transfer (ICM), and the stem-cell-associated techniques (SCAT) for the generation of gametes and ultimately embryos of highly endangered species, such as the northern white rhinoceros (Ceratotherium simum cottoni) of which only two female individuals are left. Both, ART and aART greatly depend on and benefit from the rapidly evolving cryopreservation techniques and biobanking not only of genetic, but also of viable cellular materials suitable for the generation of induced pluripotent stem cells (iPSC). The availability of cryopreserved materials bridges gaps in time and space, thereby optimizing the available genetic variability and enhancing the chance to restore viable populations.