The common goal of preventing endangered species from reaching extinction unites zoo staff and conservationists. Although their approaches might differ, both aim to maximize male fertility potential, either through semen collection and biobanking or in terms of managing natural habitat (in situ) or captive (ex situ) breeding programs. Comizzoli (2015) explores the reproductive technology advances available that enable increased participation from biobanks in endangered species conservation through preservation of male fertility.1
One of the main aims of endangered species conservation is to preserve diversity within populations and within banked genetic materials. Collecting and preserving viable semen from as many males as possible is one approach. Advances in reproductive technology in humans and domestic species, such as testicular tissue preservation, mean that other modalities are also available to scientists. By employing as many approaches as possible in both population conservation and biobanking, researchers hope to preserve diversity for sustainable repopulation efforts.
Genetic resource banks, in addition to maintaining population diversity, also assist breeding programs through the transfer of genetic materials rather than individual animals between facilities. However, the lack of information regarding reproduction in many endangered species hampers successful programs. Without detailed knowledge of reproductive hormonal cycles or optimal processing and storage protocols for harvested semen, efforts to preserve male genetic material for successful impregnation by artificial insemination (AI) may be futile.
Using details from domestic species where semen collection, storage and AI are successful, researchers can use comparative sperm cryobiology to predict optimal conditions for endangered species. Sperm concentrations and semen characteristics vary among species; this requires researchers to select the correct buffers, extenders and preservatives for viable storage. Extending cryopreservation techniques from other mammals such as bulls has seen success in AI for the black-footed ferret and in the establishment of semen banks for the giant panda. Unfortunately, AI in marsupials has not been as successful since the freezing process damages sperm motility, and even less is known about semen preservation in reptiles and birds.
Newer advances in reproductive technology for fertility preservation may hold more options. Harvesting genetic materials in its early stages as germ cells might facilitate storage more easily. Techniques such as stem cell isolation for storage or in vitro culture, and using a host for in vivo grafting, might be appropriate for banking testicular tissue for future fertility. The author notes that induction of pluripotency has been successful in male fertility preservation of snow leopards.
Considering alternative storage conditions could also benefit biobanking for endangered species conservation. Comizzoli notes that lyophilization or desiccation by freeze-drying may be easier to apply and more cost-effective in the field. Furthermore, researchers can store dried semen samples at room temperature instead of using expensive and complicated cryostorage.
Crossover from research in human biology could also benefit endangered species conservation through male fertility preservation and biobanking. As genomics and other –omics technologies advance, procedures such as cloning become more available, thus suggesting the value of preserving as wide a variety of biomaterials as possible. Zoos and conservationists thus need to work together to ensure that new techniques can be applied as quickly as possible in emergency situations. Biobanks show great potential in being part of fertility preservation networks for endangered species conservation, especially with regard to male fertility preservation.
1. Comizzoli, P. (2015) “Biobanking efforts and new advances in male fertility preservation for rare and endangered species,” Asian Journal of Andrology, 17(4) (pp. 640–645), doi: 10.4103/1008-682X.153849.