Disruption of axoneme integrity and dynein arm defects in sperm of Pih1d3−/− mice. (A) TEM of the midpiece (a–d) and principal piece (e–h) of sperm collected from the cauda epididymis of adult WT (a and e) or Pih1d32/2 (b–d and f–h) mice. Boxed areas are shown at higher magnification in the insets. Red arrows and arrowheads indicate ODAs and IDAs, respectively, in WT sperm or their loss in Pih1d3−/− sperm. Red asterisks indicate loss of the 9+2 structural organization of microtubules in Pih1d3-deficient sperm. Bars, 200 nm. (B) Quantitation of ODAs, IDAs, and peripheral doublet microtubules in sperm of WT and Pih1d3−/− mice. The numbers of ODAs and IDAs in TEM sections of 14 WT sperm and 19 Pih1d3−/− sperm were counted, and the average number of each per sperm was calculated: 0.89 ODAs and 2.05 IDAs per mutant sperm, compared with 8.07 ODAs and 6.00 IDAs per WT sperm. Peripheral-doublet microtubules in 39 Pih1d3−/− sperm were also counted, with 17 sperm showing nine intact doublets (closed diamonds), 10 sperm showing nine abnormal doublets (open diamonds), and 12 sperm showing a reduced number of doublets (filled triangles).