structural and functional aspects of bufo americanus spermatozoa effects of inactivation and reactivation very little is known about the effects of manipulating toad sperm activity in vitro and such information is important in the development of a genetic resource bank for bufonid species the specific objectives of this study were to 1 identify the optimal inactivation and reactivation solutions for toad spermatozoa collected in urine 2 establish the length of time toad spermatozoa can be exposed to an inactivation buffer and still resume motility upon reactivation 3 evaluate the consequence of inactivation on specific sperm characteristics and 4 characterize the sperm mitochondria vesicle mv and its relationship to motility reactivated sperm motility was similar after inactivation in either simplified amphibian ringers sar solution or deboers db solution diluting the buffer by 80 with water provided the best method for reactivating sperm dilutions with nacl solutions 1050 mm produced inferior results sarinactivated spermatozoa could remain suspended up to 4 hr and still regain 25 of initial motility upon reactivation in water compared to the controls sperm motility was greater p001 over time for samples treated with sar although forward progression was significantly lower furthermore sar treatment resulted in sperm samples with a greater number of viable morphologically normal and intact mvs over time electron microscopy and fluorescent staining confirmed that the toad sperms mv contains a large number of active mitochondria with very few other cytoplasmic structures nearly all spermatozoa exhibiting motility had an intact mv and dissociation of this structure was clearly related to motility loss in conclusion toad spermatozoa can be effectively inactivated and reactivated by varying the osmolality of the external solutions and although sperm forward progression is reduced all other characteristics are well maintained moreover the increased number of spermatozoa with intact mv after inactivation suggests the process may help preserve this important structure