Fig. 1. Boar spermatozoa stained with DiIC16 by back-exchange from BSA-DiIC16. Live spermatozoa (A,B,C and upper sperm in D) showed uniform fluorescence throughout the plasma membrane with varying numbers of small strongly fluorescent particles attached to the head region. Dead sperm (lower sperm in D) were typically heavily stained on the acrosomal region (see Fig. 3 for definitions of compartments within the sperm head region). Bar, 4 µm.