Cryopreservation of African lungfish (protopterus aethiopicus) sperm using egg yolk, skimmed milk extenders and dimethyl-sulfoxide and glycerol cryoprotectants

Abstract

This study aimed at establishing the effects of cryopreservation on the spermatozoa quality of lungfish semen using two extenders and two cryoprotectants. Egg yolk and skimmed milk extenders both at 10% concentration, dimethyl-sulfoxide (DMSO) and glycerol cryoprotectants at 5% and 8% respectively were used for cryopreservation. Egg yolk extender was used with each of the cryoprotectants separately as it was for skimmed milk. Live mature male lungfish were obtained from Ggaba fish landing site on Lake Victoria and transported to COVAB on ice. After milt extraction, sperm quality measures of the fresh milt were established and the milt was then frozen under different extender-cryoprotectant mixtures in cryogenic straws following the freezing procedure in a Styrofoam box and later transferred into liquid nitrogen tank at -1960C. Sperm motility and live percentages of the cryopreserved milt were obtained at 0, 1 and 24 hours. After 24 hours of cryopreservation, 10% egg yolk + 5% DMSO mixture had the highest sperm motility (5.2 ± 1.04) % and second highest live sperm percentage (87.5 ± 0.87) % while 10% skimmed milk + 8% glycerol mixture showed the second highest sperm motility (3.7 ± 0.29) % and highest live sperm percentage (87.7 ± 1.15) %. There was a decline in both motility and live sperm percentage as hours of cryopreservation progressed in all the extender-cryoprotectant mixtures used but this decline was much greater in sperm motility than live sperm percentage. African lungfish (Protopterus aethiopicus) spermatozoa can be cryopreserved whereby 10% egg yolk was found a better extender than 10% skimmed milk and 5% DMSO found a better cryoprotectant than 8% glycerol.