A non-invasive method for obtaining spermatozoa from birds

摘要

Avian spermatozoa show remarkable morphological variation (Ballowitz 1888, Retzius 1909, McFarlane 1963, 1971, Koehler 1995). Although the sperm of relatively few species have been described in detail, it is clear that fundamental differences exist between the sperm of passerines and non-passerines (Humphreys 1972, Henley et al. 1978, Thurston & Hess 1987, Koehler 1995, Jamieson 1999). Passerine sperm are relatively long and possess a pointed acrosome, helically shaped head and, most characteristically, an elongated midpiece comprising a mitochondria! helix around the flagellum. Several factors are thought to influence the evolution of sperm shape and function: (1) phylogeny - taxonomists have routinely used sperm to distinguish between different taxa (Baccetti 1987, 1991, Jamieson 1999); and (2) post-copulatory sexual selection consisting of sperm competition and cryptic female choice - sperm competition will select for sperm traits that increase a male's chance of fertilization in a competitive situation (Briskie et al. 1997, see Snook 2005 for review); but whilst passing through the female reproductive tract sperm have to overcome the chemical and physical obstacles by which females select a tiny subset of sperm (Birkhead et al 1993).