Criopreservation of Pacu sperm (Piaractus mesopotamicus, Holmberg, 1887)

Abstract Due to the absence of effective cryopreservation methods for oocytes in fish, there has been a significant focus on protocols for the cryopreservation of male gametes to maintain genetic diversity in captive populations. This study evaluated the efficiency of various penetrating cryoprotectants that may lead to better conservation of Piaractus mesopotamicus sperm characteristics. The sperm samples were collected from 14 wild males by applying light abdominal compressions and diluted in Beltsville Thawing Solution (BTS), along with the following cryoprotectants at concentrations of 5%, 7.5%, 10%, 12.5%, and 15%: dimethyl sulfoxide (DMSO), glycerol, and methanol. Kinetics of spermatozoa and cellular integrity was estimated after thawing. Sperm motility was observed to be nil for all samples for glycerol concentrations higher than 7.5%. Usage of DMSO showed less than 11% motility and less than 19 s duration of motility at all concentrations. Sperm motility was greater than 20% with a > 30 s period of motility when using methanol. We recommend, based on our observations, that using 7.5% methanol added to BTS diluent exhibits the best sperm kinetics and cell functionality (P < .05) for sperm cryopreservation of Pacu (P. mesopotamicus).