Cryopreservation and other assisted reproductive technologies for the conservation of threatened amphibians and reptiles: bringing the ARTs up to speed

Abstract

Amphibians and reptiles are experiencing serious declines, with the number of threatened species and extinctions growing rapidly as the modern biodiversity crisis unfolds. For amphibians, the panzootic of chytridiomycosis is a major driver. For reptiles, habitat loss and harvesting from the wild are key threats. Cryopreservation and other assisted reproductive technologies (ARTs) could play a role in slowing the loss of amphibian and reptile biodiversity and managing threatened populations through genome storage and the production of live animals from stored material. These vertebrate classes are at different stages of development in cryopreservation and other ARTs, and each class faces different technical challenges arising from the separate evolutionary end-points of their reproductive biology. For amphibians, the generation of live offspring from cryopreserved spermatozoa has been achieved, but the cryopreservation of oocytes and embryos remains elusive. With reptiles, spermatozoa have been cryopreserved in a few species, but no offspring from cryopreserved spermatozoa have been reported, and the generation of live young from AI has only occurred in a small number of species. Cryopreservation and ARTs are more developed and advanced for amphibians than reptiles. Future work on both groups needs to concentrate on achieving proof of concept examples that demonstrate the use of genome storage and ARTs in successfully recovering threatened species to increase awareness and support for this approach to conservation.

Island of opportunity: can New Guinea protect amphibians from a globally emerging pathogen?

“…2014b). Effective safeguarding of populations requires action before chytrid arrives in New Guinea, such as establishing and understanding captive breeding of frog species, and gene banking a representative sample to preserve and store genetic diversity (Clulow and Clulow ).…”

New Weapons in the Toad Toolkit: A Review of Methods to Control and Mitigate the Biodiversity Impacts of Invasive Cane Toads (Rhinella Marina)

“…Although the ideal solution for managing declining populations is to arrest the cause(s) of decline, this is not always possible in the time frame required to prevent the erosion of genetic diversity. In such cases, genome banking and assisted reproductive technologies could play a pivotal role in preventing genetic diversity loss, and in reversing the effects of inbreeding and genetic bottlenecks through the production of live animals from genetic material stored prior to decline (Clulow and Clulow 2016).…”

“…Encouragingly, work has already begun to develop protocols for collection and cryopreservation of varanid spermatozoa (one of the taxa most heavily impacted by toads, and a logical starting point for reptile genome storage; see Clulow and Clulow 2016) and on the AI procedures required to use cryopreserved sperm to restore genes. Targeted collection and storage of spermatozoa is a realistic goal in the short to medium time frame available before toads cause further loss of genetic diversity in many wild populations of predatory reptiles and marsupials (Clulow and Clulow 2016). Preliminary studies have successfully collected spermatozoa from live animals via electroejaculation, and from animals postmortem.…”

“…Optimization of these techniques in the near future will enable collection and permanent storage of spermatozoa from wild populations in advance of the toad-invasion front, in facilities that are now available in Australia and elsewhere. This material will then be available to restore genetic diversity postdecline via AI into wild females, potentially providing genetic rescue (Clulow and Clulow 2016).…”

Biomaterials repositories: the science and business of biobanking

“…The second session, 'Biobanking in Practice,' provided an interesting contrast between oocyte vitrification for the treatment of human infertility and the application of sperm cryopreservation to endangered species conservation (Santymire 2016). The third session, 'Unique Challenges to Cryopreservation,' highlighted the diversity of reproductive mechanisms between fish (Torres et al 2016), reptiles and amphibians (Clulow and Clulow 2016), and mammals (Pukazhenthi 2016) and the importance of tailoring cryopreservation protocols for each taxa. The fourth and final session, 'Management of Biospecimens,' addressed the significant logistical challenges for maintaining these large repositories of genetic material and transporting these samples between countries in the context of the Nagoya Protocol (Comizzoli and Holt 2016).…”