Light microscopy of emu (Dromaius novaehollandiae) sperm: preparatory technique, morphological features and morphometry

A comprehensive morphological 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 structure was visualized by making conventional semen smears from samples collected from the distal ductus deferens and fixed in 2.5% glutaraldehyde. This was followed by air-drying the smears and staining with a Romanowsky type stain. Examination of the smears using phase contrast illumination and a 100x oil immersion lens 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 sperm were 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