By Michael Le Page. Sperm with stamina sire the healthiest, longest-lived offspring, at least in zebrafish. The finding challenges the prevailing orthodoxy about what determines the physical traits of sperm, which could have important evolutionary implications. It also suggests that the methods fertility clinics use to select sperm — which instead favour the sprinters — could be improved. One part was mixed with both eggs and water.
Sperm that live for longer before fertilising an egg produce healthier offspring -- according to new research from the University of East Anglia and Uppsala University in Sweden. New research published today shows that longer-lived sperm in an ejaculate of a zebrafish male produce offspring with longer and healthier lifespans -- who in turn produce more and healthier offspring themselves -- than the shorter-lived sperm in the same ejaculate. The findings may have important implications for human reproduction and fertility, particularly in the context of assisted fertilisation technologies. Lead researcher Dr Simone Immler, from UEA's School of Biological Sciences, said: "One male produces thousands to millions of sperm in a single ejaculate but only very few end up fertilizing an egg. The research team performed in vitro fertilisations by collecting gametes from males and females. They then split the ejaculate of a male into two halves. In one half, they selected for shorter-lived sperm and in the other for longer lived sperm.
Back to Your pregnancy and baby guide. Getting pregnant conception happens when a man's sperm fertilises a woman's egg. For some women this happens quickly, but for others it can take longer. Out of every couples trying for a baby, 80 to 90 will get pregnant within 1 year.
It has long been held that the window lasts only 3 days, allowing 2 days for survival of ejaculated sperm and at most a day for egg survival after ovulation. But pregnancy lengths in higher primates monkeys, apes, and humans seemingly vary twice as much as in other mammals. It is well known that female bats can store sperm for months between copulation and fertilization. But sperm storage has rarely been considered for primates. It has also been shown that human sperm can survive for at least 5 days in the uterus, but no attempt has been made to identify an upper limit.