RESUMEN
A variety of media were compared for their ability to sustain the motility of tammar wallaby spermatozoa over an 8-h period following swim-up from coagulated semen. The study demonstrated that a modified Tyrode's solution, Biggers, Whitter and Whittingham medium (BWW) was significantly better than any of the other assessed media in supporting wallaby sperm motility. After 8h of incubation in BWW, motility was maintained at 79.3±9.3%, with 77.0±10.4% rapid and 65.7±8.7% progressively motile spermatozoa. By contrast, motility was <10% at the same 8-h time point in all of the other media assessed. After 2h of incubation in BWW, tammar spermatozoa consumed more oxygen than their counterparts in PBS (52.0±2.7 vs 75.0±6.6µL per 108 spermatozoa per 2h; P<0.001). Motility was not enhanced in any of these media by the addition of 5mM N-acetyl-D-glucosamine, the major energy substrate in wallaby semen. However, addition of dibutyryl cAMP and pentoxifylline in BWW resulted in the extremely rapid induction of hyperactivated motility in the entire sperm population. This burst of hyperactivated motility was entirely dependent on calcium in BWW and significantly inhibited by calmidazolium, a calmodulin inhibitor. A set of computer-assisted sperm analysis parameters were identified that permitted the accurate quantification of hyperactivation rates in this species. This is the first comparative analysis of media for harvesting and incubating marsupial spermatozoa and the first record of hyperactivated motility in any marsupial species.