Fig. 4. Morphological abnormalities of epididymal sperm from RIM-BP3 knockout mice. (A) Scanning electron micrographs. (a) Abnormal head shaping, tail detachment (arrowheads) and bending (arrow) occur in sperm of the mutant mouse. Scale bar: 20 µm. (b,c) Higher magnification of abnormal spermatid heads lacking the hook-shaped appearance typical of a normal spermatid from the wild-type mouse (d). Scale bar in d: 2 µm in b-d. (B) Transmission electron micrographs. Deformed nuclei were observed (asterisk) and most of the sperm heads in mutant mice display a detached acrosome (black arrow). Acr, acrosome; Nu, nucleus. Scale bars: 1 µm.