Cryopreservation of tambaqui semen using a dry shipper and a programmed freezing machine

Abstract

Tambaqui (Colossoma macropomum) is a native freshwater fish that is of great importance for Brazilian aquaculture. Because of this importance, several techniques have been developed to improve the reproduction of this species in captivity. One of these techniques is the cryopreservation of sperm. In an effort to increase the efficiency of cryopreservation protocols, researchers have tried to determine suitable diluting solutions and freezing methods, which will provide a better post-thaw sperm quality. Thus, this study aimed to evaluate the efficiency of different diluents and freezing methods for the cryopreservation of tambaqui (C. macropomum) sperm. Samples of fresh semen were diluted in different treatments (Glucose 5% + 10% Dimethyl sulfoxide - DMSO, Glucose 5% + 10% Methyl glycol - MG, BTS + 10% DMSO and BTS + 10% MG) at a 1:9 dilution rate and frozen in a programmed freezing machine and a dry shipper. The semen samples were thawed and evaluated for vitality, sperm morphology and kinetics. Cryopreserved semen with DMSO and using the programmed freezing machine provided a greater percentage of motile sperm (15.44 ± 1.04%) after thawing compared to the dry shipper (3.99 ± 0.55%), regardless of the diluent. Additionally, DMSO showed better sperm velocities than MG regardless of the freezing method and the extender employed. A higher percentage of living spermatozoa was observed when glucose (37.28 ± 1.32%) (regardless of the freezing method and cryoprotectant) and DMSO (37.98 ± 1.25%) was used in the programmed freezing machine. For morphology, a greater amount of normal spermatozoa (46.10 ± 1.82%) was observed when the semen was cryopreserved using a freezing machine programmed with DMSO as the cryoprotectant and Glucose or BTS (38.16 ± 1.9% and 39.26 ± 1.87%, respectively) as extenders. Therefore, we suggest the use of the DMSO (10%) cryoprotectant in association with the Glucose (5%) extended in the programmed freezing machine for cryopreservation of C. macropomum semen.