Figure 5.

Female oviduct and sperm migration. The diagram shows the female tract of mammals and the three sperm guidance mechanisms, depending on the site in which they have been described to act. While rheotaxis and thermotaxis have been suggested to act mostly in long-range distances, chemotaxis is supposed to take place only in the proximity of the female egg (considering that the exact fertilization site is species-dependent). The colors represent the thermal and chemical gradient (from left to right).