Variation in sperm parameters among Mus species during preparation for fertilization

SANSEGUNDO HERNANDO, ESTER; TOURMENTE, MAXIMILIANO; ROLDAN, EDUARDO R. S.

Lisboa

Congreso; 14th Rodents et Spatium; 2014

Mammalian spermatozoa must undergo a series of changes before participating in fertilization. This physiological "switching-on" (known as "capacitation") includes modifications in the pattern of sperm movement. Upon capacitation, sperm movement changes from a linear and symmetrical trajectory to an asymmetrical, vigorous and non-linear pattern ("hyperactivation"). We compared changes associated to capacitation in spermatozoa of three species of Mus (M. musculus, M. spretus and M. spicilegus) that differ in levels of sperm competition. Spermatozoa were incubated in capacitating (mT-BH) and control (mT-H) medium, and the following parameters were quantified every 30 min: percentages of sperm that were motile, capacitated, acrosome-reacted, and hyperactivated, along with descriptors of sperm swimming velocity, and sperm ATP content. Timing of capacitation differed between the three species: the species with higher sperm competition levels achieved a higher percentage of capacitated cells in a shorter period of time. Sperm hyperactivation was characterized by an increase in curvilinear velocity and lateral head displacement, and a decrease in straight-line velocity and linearity. There was no clear pattern of association betweeen hyperactivation and sperm competition levels. Therefore, sperm competition may act on certain sperm features (e.g., timing and proportion of cells completing capacitation), whereas other sperm traits may be selected by cryptic female choice or male-female coevolution.