Living sperm (spermatozoa) - like other cells - require suitable conditions for survival outside the body. The chemical make-up of the fluid medium in which they are suspended and the temperature at which it is maintained are two key variables. The technique of in vitro fertilisation (ivf) requires that sperm are kept in optimal condition for variable amounts of time before they are placed in contact with eggs for fertilisation. This can be done either by freezing and then re-thawing when required, or by incubation at normal body temperature for up to several hours in a suitable fluid medium (liu, clarke, and baker, 1986). The fluid has to be isotonic for the sperm and contain nutrients and other materials for the sperms’ survival. One of the difficulties in keeping sperm alive in a culture dish is that they produce oxygen free radicals. These are highly reactive molecules which at lower levels are thought to control normal sperm function, but which can become damaging at higher levels (aitken, 1995; gomez and aitken, 1996).
Sperm would not survive for long in plain water - although the seminal fluid would provide some protection initially, the water is very hypotonic to the sperm cells and would soon cause them to swell and disintegrate.
