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.
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.
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.
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.
Frogs can change their sex even in pristine, pollution free settings. Past research suggested that male-to-female sex changes happening in frogs in suburban ponds may be caused by increased levels of estrogen released into the water. They found more female frogs than males in suburban areas.
Baby mice have been made with two mums and no dad, say researchers at the Chinese Academy of Sciences. It took a substantial feat of genetic engineering to break the rules of reproduction. The scientists said the "bimaternal" (two mammas) animals were healthy and went on to have pups of their own.
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.
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).
The process of changing from identifying as a boy to a girl, or vice versa, is called transitioning. The process doesn't always mean getting surgery. It can take several forms. Some are nonpermanent steps, such as choosing a new name, changing pronouns, and wearing different clothes and hairstyles.
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.
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.
The swamp wallaby is the only mammal that is permanently pregnant throughout its life according to new research about the reproductive habits of marsupials. Unlike humans, kangaroos and wallabies have two uteri. The new embryo formed at the end of pregnancy develops in the second, 'unused' uterus.
Ethical considerations preclude definitive research on the subject, but it's safe to say that human DNA has become so different from that of other animals that interbreeding would likely be impossible.
For some, of course, it's normal to only have one or a couple of offspring in a lifetime. But swamp wallabies, small hopping marsupials found throughout eastern Australia, are far outside the norm: New research suggests that most adult females are always pregnant.
Other species of jellyfish – sequential hermaphrodites – are either male and then female, or vice-versa, but not both simultaneously. These are natural transgender jellyfish. No special treatment is necessary.
A bit confusing, yet generally speaking a unique gland determines masculinity in crustaceans, at least in those species such as lobsters, prawns, crabs and crayfish where sex does not change naturally.
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.
At first glance it looks like the single-celled organism Tetrahymena thermophila has cracked this problem in spectacular fashion. It has not two but seven sexes, and each one can mate with any of the others, which opens up the field considerably.
One species of fungi, Schizophyllum commune, really shines when it comes to gender diversity. The white, fan-shaped mushroom has more than 23,000 different sexual identities, a result of widespread differentiation in the genetic locations that govern its sexual behavior.
Many species of whiptail lizards are all female. That's right: these badass ladies figured out how clone themselves, so they wouldn't have to bother having sex with males to maintain their species. This natural form of cloning is called "parthenogenesis" — and it isn't as complicated as it sounds.
Biological sex in healthy humans is determined by the presence of the sex chromosomes in the genetic code: two X chromosomes (XX) makes a girl, whereas an X and a Y chromosome (XY) makes a boy. In this way, it is the presence or absence of the Y chromosome in a healthy human that differentiates boy from girl.