Quality of cryopreserved African catfish sperm following post-thaw storage

Abstract

Experiments were carried out to test the fertilizing capacity and viability of cryopreserved African catfish (Clarias gariepinus) sperm following post-thaw storage at 4°C and following activation with water. In the first experiment, cryopreserved sperm was thawed and stored in a refrigerator for time periods ranging from 0 to 96 h before being used for fertilization. In all cases sperm stored for 24 h resulted in the highest fertilization percentages (37 ± 9%) which was significantly higher than that observed with sperm used for fertilization immediately after thawing (21 ± 4%, P < 0.05). These observations were later confirmed by flow cytometric assessment of membrane integrity of spermatozoa which showed an increase of the percentage of membrane-intact cells from 2 h post-thaw (66 ± 3%) to 26 h (77 ± 3%). In the second experiment, thawed and fresh sperm of African catfish was activated with water and used for fertilization at different time periods post-activation ranging from 0 to 120 s. The highest fertilization rate with cryopreserved sperm (72 ± 12%) was observed when eggs were fertilized with sperm activated for 20 s, however, sperm cells activated for 120 s were still able to fertilize eggs, albeit at a low rate (2 ± 3%). It was also noted that in the second trial of experiment 2 cryopreserved sperm resulted in significantly higher fertilization percentages than freshly extracted semen (P < 0.05).