This deduction would receive support if it could be established that a sperm entry hole does form in living material. Gently compressed eggs formed exovates only through this hole. The holes, and exovates, were not found except at sperm entry sites.
Maternal and paternal influences before fertilization can significantly affect the ultimate reproductive output. In avian species, previous studies have shown that concentrations of testosterone T in seminal plasma vary greatly and are related to sperm quality. To our knowledge, the presence of other reproductive hormones in avian seminal plasma and their potential influences on fertility remain unstudied.
Researchers at Karolinska Institutet in Sweden have obtained the first 3D snapshots of a sperm protein attached to a complementary egg coat protein at the beginning of fertilisation. The study, which reveals a common egg protein architecture that is involved in the interaction with sperm in both mollusc and mammal, is published in the scientific journal Cell. By transmitting the genetic information to the next generation and marking the beginning of a new life, the encounter between female and male gametes at fertilisation is one of the most fundamental processes in biology.
Artificial insemination is used to improve the genetics of dairy cattle, like this bull. The goal is to spread genes for desirable traits, such as disease resistance or heat tolerance, through a population of animals in fewer generations than is possible with conventional breeding. If scientists can surmount lingering technical hurdles, the technique could prove invaluable for pigs, chickens and other livestock that are tricky to breed using artificial insemination. The technique could also aid efforts to conserve species for which semen storage is difficult, including many birds.
It is the only living member of the genus Physeter and one of three extant species in the sperm whale familyalong with the pygmy sperm whale and dwarf sperm whale of the genus Kogia. The sperm whale is a pelagic mammal with a worldwide range, and will migrate seasonally for feeding and breeding. The females cooperate to protect and nurse their young.
Long, D. Bongalhardo, J. Saxena, P.
Traumatic inseminationalso known as hypodermic inseminationis the mating practice in some species of invertebrates in which the male pierces the female's abdomen with his aedeagus and injects his sperm through the wound into her abdominal cavity hemocoel. The process is detrimental to the female's health. It creates an open wound which impairs the female until it heals, and is susceptible to infection.
In high-school health class films, sperm cells are shown zooming around with quick flicks of their tails, but they only jump into action when they are in the right chemical conditions — usually that's in the female reproductive tract. Researchers have now figured out the precise chemical switch that turns on the sperm's motors, which could lead to the development of new treatments for infertility. Scientists have long known that sperm's activity level depends on the internal pH of the sperm cell —a measure of how acidic or alkaline a substance is. They start out with acidic insides when in the male reproductive tract, but once they enter the female tract, their internal environment becomes alkaline and off they zoom toward the egg.
Back to Sexual health. Puberty can be a confusing time, because your body and your feelings are changing as you grow up. Here are answers to some of the questions that boys often ask about their bodies.