A comprehensive morphologic description of emu sperm at the light microscopy level, an
essential prerequisite for the routine evaluation of semen quality in this species, is not
currently available. In this study, sperm morphology and morphometry were evaluated using
conventionally prepared Romanowsky-stained semen smears of samples collected from the
distal ductus deferens from 15 adult birds and fixed in 2.5% glutaraldehyde. Examination of
the smears using phase contrast under 100 magnification readily resolved the various
components of the cell, namely, the acrosome, nucleus, midpiece, principal piece, and endpiece.
This technique was simple to use and produced consistently reproducible results.
Normal emu spermwere typically filiform in appearance and closely resembled sperm of the
ostrich and other non-passerine species, particularly poultry. A previously undescribed
cytoplasmic appendage, associated with the base of the head, was a novel morphologic
feature. The acrosome was short (1.84 0.31 mm; mean standard deviation), whereas the
nucleusmeasured 11.77 0.93 mmin length. The length of the segments of the flagellumwere
2.91 0.4 mmfor the midpiece, 47.45 2.8 mmfor the principal piece, and 3.69 0.82 mm for
the endpiece. The total sperm length was 67.64 3.13 mm (range, 60.14–79.49) and the
head:tail ratio was 1:4. Sperm dimensions in the emu were similar to those of other ratites.