Conservation rationale, research applications and techniques in the cryopreservation of lower vertebrate biodiversity from marine and freshwater environments

The conservation benefits of cryopreserving cells and tissues from species at risk are well illustrated in the case of fishes and amphibians. These are the most threatened vertebrate groups worldwide, with over 30% of species so far assessed being listed as threatened by the International Union for Conservation of Nature. Cryopreservation technologies now provide opportunities for the long-term storage in cryobanks of cells and tissues from these lower vertebrate taxa. Material maintained in cryobanks can be used to complement other in situ and ex situ conservation approaches. Cryobanks have been established in the United Kingdom for fishes and amphibians, drawing on specimens from zoos and aquariums, and also specimens collected in the field. Cryobanked material has to be of the highest quality to enable future exploitation in such areas as genomics, proteomics and managed breeding programmes. Currently, these cryobanks can hold viable sperm in the form of testes macerates, and material suitable for long-chain DNA mapping and cell-culturing, from somatic tissue and embryos. Successful cryobanking procedures are described here in detail. Viable oocytes and embryos have not yet been cryopreserved for fishes or amphibians. Hence, this is currently a key research area, which, if it delivers viable products for these taxa, would potentially bring major conservation and research benefits.