Changes in the flagellum morphology of intact and frozen/thawed Siberian sturgeon Acipenser baerii (Brandt) sperm during motility

Morphological investigations on the changes in flagellar beating was carrie d out on native (taken from the milt) and thawed sperm of the Siberian stur geon Acipenser baerii (Brandt). Immediately after activation, the pattern o f flagellar wave formation and distribution was the same in native and thaw ed sperm but, after 27-42 s, depending on the samples, the thawed flagella showed asymmetric and poorly developed waves. The swimming trajectories rec orded during 1-s exposure were much shorter in thawed than in native sperm after 26-28 s motility. In native sperm, the flagella remained in the same axis as the head during the entire motility course, while the head of thawe d sperm showed a right angle after 47 s. It is concluded that the freezing/ thawing procedure induces some alteration in the dynamics of flagellar beat ing in many sperm, but these sperm still show progressive displacement. The refore, the change in morphology of the flagellum during motion is a parame ter that should be taken into account in the evaluation of the impact of va rious treatments on sperm motility.