Epididymal sperm storage in Ricketts big-footed bat (Myotis ricketti)

Spermatozoa were present in the cauda epididymidis of male Rickett's big-footed bat, Myotis ricketti, from late September to early April but absent from the testes from mid November until late August. Males thus store spermatozoa in the cauda epididymidis for 4.5–6.5 months of the year. Assessments of sperm motility, movement pattern and computer-assisted sperm analysis (CASA) were carried out on spermatozoa which had been stored for over 3.5 months in the cauda epididymidis. The motility of sperm stored for the same period of time and taken from a male which died over 9 h before assessment was 86%. Four kinds of culture media were screened for their suitability for future studies of sperm motility, and a low calcium minimal capacitation medium and a hamster fertilization medium were selected. Serum testosterone (T) concentration increased dramatically in September and began to fall in October, before returning to baseline for the remainder of winter. These results indicate that high levels of T are required for spermatogenesis and spermiogenesis but not for sperm storage.