Fig. 3.

Ray sperm propulsion. (A) Schematic diagram of the sperm propulsion. The net drag force $f$, acting on each segment of both head and tail helixes, has a rotational component $f_l$ and the propulsive force $f_f$, which drives the sperm forward. From 381 samples, the average propulsion contribution from the helical head accounted for 31% of the total body. Bar = mean; error bar = SD. The detailed results of the cumulative (orange) and segmented (gray) propulsive force along with one sperm body are shown in B. The gray bars represent the segmented propulsive force of every 100 segments on the sperm body. (C) Fitting relationship between the rotational speed of tail and the forward speed of the sperm (mean ± SD). The forward speed grew with increasing tail rotational speed and the slopes for the five samples were 0.73, 1.31, 15.17, 3.40, and 7.54, respectively.