Cryobanking in aquatic species: applications and perspectives in fish germ cells

Germplasm cryobanking has a direct application in reproductive practices in marine and freshwater cultured fish species by simplifying broodstock management, and its potential has been evident also in laboratory model fish species to maintain important strains or even to reproduce them as a unique choice. This is the case of zebrafish, where several protocols have been used to preserve spermatozoa and other germ cells. Cryobanking has been also a valuable tool to preserve the genetic resources of a wide range of species and with the help of reproductive biotechnologies, such as germ cell xenotransplantation, plays an important role in genetic selection programs, biodiversity preservation platforms and assisted reproduction. In fish, according to the IUCN Red List (2014), there are 2,222 threatened species in the word, and therefore cryopreservation could be a secure method to preserve the genetic material of these species, providing the opportunity to maintain representative samples and further reconstruct the original strain, population or variety. The management of these banks requires technical capacity in genetics, reproductive physiology, cryobiology and data administration. Cryopreservation protocols must be carefully designed for each species and each type of cell. This review will be focused in the potential of cryobanking in fish species, embracing freshwater and marine fish species and different cell types such as spermatozoa, spermatogonia and somatic cells