Evaluation of cryodamage in small abalone, Haliotis diversicolor, spermatozoa by using a flow cytometer

We used flow cytometry to determine the quality of small abalone, Haliotis diversicolor, sperm before freezing and after thawing. We investigated the effects of cryopreservation on the characteristics of small abalone semen and determined the motility and fertilization capacity of the pre-freezing and post-thawed sperm. The percentages of motility and fertility were 61 +/- 2% and 67 +/- 1%, respectively, for the post-thawed sperm and 90 +/- 4% and 92 +/- 0%, respectively, for the pre-freezing sperm. Sperm cells were stained with specific fluorescent dyes to measure plasma and acrosomal membrane integrity, mitochondrial status, oxidation level, DNA compaction, and viability through flow cytometry. The frozen-thawed sperm exhibited significantly higher mitopotential activity (p < 0.05, damaged mitochondria; 25.01 +/- 1.18%) and oxidation value (p < 0.01, free radicals; 63.79 +/- 3.93%) compared with the pre-freezing sperm. The oxidation level was the most sensitive signal of the cryopreservation-induced small abalone sperm damage. Flow cytometry is valuable for the objective, accurate, and rapid assessment of pre-freezing and post-thaw small abalone sperm quality.