Genetic rediscovery of an ‘extinct’ Galápagos giant tortoise species

their sperm. As mentioned above, if sperm were not adapted to survive (sperm longevity) inside the female’s reproductive tract, the female would be limited in her ability to maintain sperm. Males may face a trade-off between sperm competitive ability (fast-swimming sperm) and ability to be stored (long-lived and slow-swimming sperm). Sperm pre-adaptations for storage include a decreased sensitivity to sperm activation specifically, acrosomal reaction desensitization, and the presence of antioxidative enzymes. Also commonly observed and apparently important for storage is a decrease in sperm motility. In addition to changes to the spermatozoa, males may produce chemicals that increase sperm viability during their stay in the female’s reproductive tract. The notion that mate choice only occurs prior to copulation has been rejected for well over 40 years. However, the complexity of post-copulatory sexual selection and the potential for sexual conflict may be even greater than currently appreciated if the time-frames over which events occur are lengthened by weeks, months or even years through the storage of sperm. Sperm storage remains an exciting area for future research, including the refinement of associated terminology as well as studies relating to co-evolution.