Many species of fish, like the kobudai, are known as “sequential hermaphrodites”: they can switch sex permanently at a specific point in their lives. The majority of “sequential hermaphrodites” are known as “protogynous” (Greek for “female first”): they switch from female to male.
Approximately 5% of animal species have the ability to change sex throughout their lives to maximize reproductive success. Clownfish form pairs that live together for years in symbiosis with an anemone.
About 500 species of fish change sex in adulthood, a process known as sequential hermaphroditism. Animals that switch from female to male, like the bluehead wrasse, exhibit protogyny, while animals that switch from male to female, like clownfish, exhibit protandry.
Unlike most other sequential hermaphrodites that make the switch and stick with it, hawkfish can switch back again. Female-turned-male hawkfish may revert to female if, say, their new harem loses too many females or if a larger male challenges them.
Hermaphroditic animals—mostly invertebrates such as worms, bryozoans (moss animals), trematodes (flukes), snails, slugs, and barnacles—are usually parasitic, slow-moving, or permanently attached to another animal or plant.
Researchers have identified more than 500 fish species that regularly change sex as adults. Clown fish begin life as males, then change into females, and kobudai do the opposite. Some species, including gobies, can change sex back and forth. The transformation may be triggered by age, size, or social status.
It is possible for a female chicken to take on external characteristics of a male, a phenomenon referred to as sex reversal. (To date, spontaneous sex reversal from male to female has not been reported.)
Waters says the process uncovered for the first time a gene, called AMH [for Anti-Müllerian hormone], on the oldest of the platypus Y chromosomes that appears to determine if an animal becomes male. "If an animal has that gene it will act as a master switch to turn on testis development," he says.
The threes sexes of the Pleodorina starrii algae are male, female, and a third sex that researchers call bisexual in reference to the fact that it can produce both male and female sex cells in a single genotype and exists due to normal expression of the species' genes.
Caltech scientists have discovered a new species of worm thriving in the extreme environment of Mono Lake. This new species, temporarily dubbed Auanema sp., has three different sexes, can survive 500 times the lethal human dose of arsenic, and carries its young inside its body like a kangaroo.
A rough estimate of the number of hermaphroditic animal species is 65,000. The percentage of animal species that are hermaphroditic is about 5% in all animal species, or 33% excluding insects.
Based on the sole criterion of production of reproductive cells, there are two and only two sexes: the female sex, capable of producing large gametes (ovules), and the male sex, which produces small gametes (spermatozoa).
An intersex animal is one possessing the characteristics of both sexes. Intersex animals, also called pseudohermaphrodites or hermaphrodites, are classified on the basis of their gonads.
Though scientists are still investigating the specifics of the various species, crocodilians -- including crocodiles, alligators, caimans and gharials -- typically produce inherently female embryos, which can become male when certain environmental conditions are met.
The hen does not completely change into a rooster, however. This transition is limited to making the bird phenotypically male, meaning that although the hen will develop physical characteristics that will make her look male, she will remain genetically female.
There are reports of these birds producing semen capable of fathering offspring but most will not do so, nor will they lay eggs. The reverse switch doesn't seem to happen. Roosters don't automatically become hens.
A hen to rooster transformation is most definitely possible no matter how impossible it may seem. This occurrence usually occurs due to a genetic condition where the chickens only functioning ovary is damaged. The non-functioning ovary can then start to develop into a structure known as an avo-testis.
Other scientists believe that the big sharks, like some other species, change sex when they reach a certain size: males become females. The switch may ensure survival by allowing the largest, most experienced sharks to give birth to young.
As far as they know, frogs can only change sex during their tadpole phase.
All oysters start life as male, but most will change permanently to female after about a year. Their reproductive organs produce both sperm and eggs, giving them the capability to change gender. It is, therefore, possible for an oyster to fertilize its own eggs.
Indeed, Pliny says, the critter is “popularly believed to be bisexual and to become male and female in alternate years.” In Aesop's fable “The Hyenas,” they “change their sex each year.” Even Ernest Hemingway called the hyena a “hermaphroditic self-eating devourer of the dead, trailer of calving cows, ham-stringer, ...
Gynandromorphs (“gyne” from Greek meaning female, “andro” for male, and “morph” meaning variety) are individual animals that have both genetically male and female tissues and often have observable male and female characteristics.
Female Pseudohermaphrodite Dogs
Female pseudohermaphrodites have XX chromosomes and ovaries but the internal and external genitals appear masculine due to excess amounts of testosterone. In mild cases, the pet may just have an enlarged clitoris and otherwise appear normal.