Effects of Different Cryoprotectants, Cryoprotectant Concentrations and Extenders for Short Term Cryopreservation of African Catfish Clarias gariepinus (Burchell, 1822) Milt

Abstract

Abstract Aquaculture of Clarias gariepinus is on the increase in Africa. Among the challenges to its production is the scarcity and high cost of broodstocks and sacrifice of the male during induced breeding. Cryopreservation of the milt of the species is a solution to this challenge. However, cryopreservation success depends on right extender, cryoprotectant and concentration. Phosphate buffered solution (PBS) and freshwater ringer solution (extenders), Dimethyl sulphoxide (DMSO), glycerol and glucose (cryoprotectants) at 5% and 10% concentrations were used to investigate the best cryoprotectants, cryoprotectant concentrations and extenders for short term cryopreservation of Clarias gariepinus milt. Control using fresh milt was also set up. Fifteen each of matured male and female broodstocks of C. gariepinus, weighing between 1.1 – 2.0kg were used for the experiment. analysis of variance (ANOVA), followed by comparison of means using Duncan’s Multiple Range Test. Percentage data were calculated prior to analysis. All statistical analyses were performed using SPSS software (Version 16.0, 2005). Dimethyl sulphoxide + phosphate buffered solution (DP) had the highest fertilization rate of 65% and 78% for 5 and 10% cryoprotectant concentrations respectively. Lowest fertilization rate was in glucose + freshwater ringer solution (GF) with 5 and 10% concentration giving 5% and 8% fertilization. Fertilization in control was 88%. Hatching and survival followed fertilization trend with DP 10% > DP 5% > DF 10% > GLP 10% > DF 5% > GLP 5 % > GLF 10% > GLF 5% > GP 10% > GP 5% > GF 10% > GF 5%. Good quality sperm used, non-toxicity and high permeability of DMSO, osmolality effect of PBS on milt were some of the factors responsible for the success of the cryopreservation. 10% DMSO and PBS are the best cryoprotectant and extender for short term cryopreservation of African catfish milt for at least 5 days.