Almost all snakes reproduce sexually, with the participation of female and male. Only certain species are capable of parthenogenesis, i.e. the reproduction is not transmitted sexually, and from unfertilized eggs without the participation of a male. There among the snakes, as a rare exception, and true hermaphrodites, i.e. individuals who are simultaneously female and male. Such exceptional case was recorded on the small island of Queimada-Grande, South America. There were found the snake, dubbed the island bothrops, among which, in addition to ordinary females and males, meet bisexual individuals who make up the majority of the population. These individuals are females, while the ovaries are the male copulatory organs and Mature testes. Such individuals may in some cases play the role of females and to breed, and the males are fertilizing other females (ordinary or hermaphrodite). The existence in the population of the island bothrops such unusual females is so efficient, the need for normal males has dropped, and their share in recent years has declined.
The female from the male in the overwhelming majority of snake species difficult to distinguish. The serpent the visible Continue reading
Extreme situation. Venomous snakes and lizards
A large variety of venomous snakes occur in the tropics, however, some space of the globe completely devoid of poisonous snakes, including New Zealand, Cuba, Haiti, Jamaica, Puerto Rico and the Polynesian Islands. Some species of snakes are more aggressive than others, and can attack with no visible signs of provocation. However, aggression is the exception rather than the rule. The danger from snakes cannot be ignored in areas of high temperature where they are active day and night during the hot months. In cold weather they are passive or hibernate. In arid and semi-arid lands of the snake is more active early in the morning, afternoon they behave sluggish and hiding in the shadows. Many snakes are active only at night.
Considered the most poisonous vipers from Europe, Asia and Africa; copper-red and cotton, maksinova snakes in North America; shrubby and some other varieties in the American tropics. This is a long snake with venomous teeth.
Ordinary vipers and vipers “trench” (found in the pits) typically have a stout body and flat head.
Widely known varieties of the present (normal) vipers are found only in Europe, the Russell’s Viper in India, Viper with a hood in South Africa, American Viper — in dry areas of Africa and Arabia, Gabon-sky in tropical Continue reading
Found a gene that determines, will become a gamete sperm or egg
Japanese genetics found in the DNA of fish unusual gene that determines it, will the sex cell sperm or egg, and changed his work so that in the ovaries of female fish began to form spermatozoa and in the testes of males of the egg, according to a paper published in the journal Science .
“We knew that gametes can turn into sperm and ovum, but no one has suggested that these cells in the vertebrate animals have a special gene”switch” that determines their fate – to become a sperm or egg. Our results indicate that the cell is able to go all the way. This is a very important and unexpected discovery” – quoted by RIA “Novosti” scientist Minoru Tanaka from the Institute of General biology of Japan in the city of Okazaki.
Tanaka and his colleagues made this unusual discovery, watching the development of germ cells in testes and ovaries rice fish-oriii (Oryzias latipes). During maturation of sperm and egg cells, researchers monitored changes in the level of activity of different genes, trying to find the differences between future male and female reproductive cells.
The attention of scientists was attracted to gene foxl3 – “archival copy” of the gene foxl2, which is responsible for growth of eggs and maintaining Continue reading