The life of the cottony cushion scale insect reads like something from the most ridiculous of tabloid newspapers. Dad leaves parasitic body parts in his own daughter, which produce sperm that fertilise her eggs. He is both father and grandfather to his own grandchildren.
Republish our articles for free, online or in print, under Creative Commons licence. A first international congress was devoted to it in To understand evolution, scientists start by observing living things, and by defining their characteristics.
In his lab, Pitnick engineers the heads of fruit fly sperm to glow a ghostly red and green so that he can observe them moving through dissected female fly reproductive tracts. He hopes his work will help reveal how sperm behave within female bodies, an area of research that's still in its relative infancy. These kinds of innovations could one day explain the great diversity of sperm shape and size across the animal kingdom.
The new study by Harini Iyer and Phillip A. The population of stem cells that develop into sperm, called spermatogonial stem cells SSCsmust continually renew themselves, while also differentiating into mature sperm. Too much self-renewal can create tumors and defects in differentiation can lead to infertility through malformed sperm.
Timothy James WisniewskiSyracuse University. The present study looks at the interaction between species recognition and mate choice within a set of sympatric species. In Mexico, a complex of species of internally fertilizing, viviparous fishes Genus Poeciliopsis live sympatrically with each other and with an array of clonal females.
Figenschou, I. Folstad, G. Rudolfsen, S.
Reinartz, Ellen. The influence of sperm competition and parasites on reproductive strategies in simultaneously hermaphroditic land snails. Downloads: Statistics Overview.
Spermalso called spermatozoon, plural spermatozoamale reproductive cellproduced by most animals. With the exception of nematode worms, decapods e. In higher vertebrates, especially mammals, sperm are produced in the testes. The sperm unites with fertilizes an ovum egg of the female to produce a new offspring.
The sperm that reaches the egg first gets to fertilise it. When multiple males are competing, this race can lead to the evolution of, for example, faster-swimming sperm. Now imagine a more difficult scenario: before its sperm can swim to the egg, the male would first need to race to make the sperm.
HHMI is a science philanthropy whose mission is to advance basic biomedical research and science education for the benefit of humanity. HHMI empowers exceptional scientists and students to pursue fundamental questions in basic science. A study of sperm formation in the worm Caenorhabditis elegans may point toward a major cause of infertility in humans.