Intact plasma membrane and functional mitochondria are important attributes for the fertilization capacity of fish sperm. In the present study, dimethyl sulfoxide (Me2SO) and glycine were investigated in an effort to improve plasma membrane integrity and mitochondrial function in cryopreserved striped bass (Morone saxatilis) sperm. Prior to freezing, no concentration of Me2SO (2.5, 5 or 10%) was found to affect (P > 0:05) the integrity of plasma membranes after sperm were exposed for 10 min. However, mitochondrial function decreased (P < 0:01) with increasing Me2SO
concentration. Both fluorescent staining and microscopic examination of the ultrastructure of post-thaw plasma membranes indicated that with increasing Me2SO concentration, plasma membranes were better protected, and 10%
Me2SO had the highest percentage of sperm with plasma membranes intact. However, sperm mitochondrial function decreased (P < 0:05) with increasing Me2SO concentration. The inverse relationship between plasma membrane integrity
and mitochondrial function, given the Me2SO concentration, suggests that care must be taken to select Me2SO concentration that will maximize the protection of both plasma membranes and mitochondrial function. The addition
of glycine to the cryomedia increased (P < 0:05) the percentage of sperm with post-thaw functional mitochondria and ATP content. However glycine did not provide (P > 0:05) protection to post-thaw plasma membrane integrity.
The highest percentage of sperm with both intact plasma membranes and functional mitochondria was obtained with 7.5% Me2SO and 75mM glycine