rakesh dwivedi

Non-genetic sex-determination systems See also: Temperature-dependent sex determination Many other sex-determination systems exist. In some species of reptiles, including alligators, some turtles, and the tuatara, sex is determined by the temperature at which the egg is incubated. Some species, such as some snails, practice sex change: adults start out male, then become female. In tropical clown fish, the dominant individual in a group becomes female while the other ones are male, and bluehead wrasses (Thalassoma bifasciatum) are the reverse. In the marine worm Bonellia viridis, larvae become males if they make physical contact with a female, and females if they end up on the bare sea floor. Some species, however, have no sex-determination system. Hermaphrodites include the common earthworm and certain species of snails. A few species of fish, reptiles, and insects reproduce by parthenogenesis and are female altogether. In some arthropods, sex is determined by infection, as when Bacteria of the genus Wolbachia alter their sexuality; some species consist entirely of ZZ individuals, with sex determined by the presence of Wolbachia. Other unusual systems (this section is still being researched): Swordtail fish The Chironomus midge species The Platypus has 10 sex chromosomes[5] but lacks the mammalian sex-determining gene SRY, meaning that the process of sex determination in the Platypus remains unknown.